Delirium prevalence and incidence in acutely admitted older patients: an observational cohort study

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As the population ages and more people live with dementia, updated and accurate estimates of delirium prevalence are important. The primary aim of this study was to identify delirium point prevalence in the emergency department and incidence during hospitalisation. Our secondary aim was to compare outcomes: length of stay, need for a higher level of care, and mortality after discharge in patients with and without delirium. Methods In this unselected observational cohort study, all older adults aged 65 years or above acutely admitted to the emergency department of a large Norwegian hospital during a 5-day and 4-night midweek period, were screened for delirium by the 4 “A”s test. A final consensus delirium diagnosis was made based on review of all available information in the patients’ electronic health record to consider if The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition’s criteria (DSM-V) for delirium were fulfilled. Results Of 240 patients assessed, 14% (n = 33) fulfilled DSM-V criteria for delirium in the emergency department, and 8% (n = 17) of the remaining 207 patients developed delirium later during the hospitalization. Only 4 of the 50 patients with delirium (8%) had a documented diagnosis of delirium in their discharge summary. For patients with delirium, the current hospital admission was more often a readmission (42% vs 18%, p < 0.001). Delirium patients also had longer hospitalizations (4 vs 2 days, p < 0.001), and higher 9-month mortality (52% vs 13%, p < 0.001), corrected for age, gender and severity of acute illness by The National Early Warning Score 2. Conclusions Delirium was common and underdiagnosed in our study and associated with unfavourable outcomes for the patients. Delirium prevention, identification and management should be key priorities for the health care system. Trial registration Our article does not report results of a health care intervention, and the protocol is not registered in a trial registry. delirium prevalence occurrence older adults incidence acute-hospital emergency-department outcomes mortality length-of-stay screening 4AT under-reported Figures Figure 1 Figure 2 Strengths and limitations of this study We included 92% of all acutely admitted patients in the study period, which is high compared to similar studies and a strength in providing a precise and updated estimate of delirium occurrence. We registered both delirium prevalence in the emergency department and incidence during the rest of the hospitalisation. Delirium assessment was done systematically and independently by two geriatricians, with high interrater reliability, based on The Diagnostic and Statistical Manual of Mental Disorders, Fifth Editions criteria. We compared outcomes for patients with and without delirium but without data on comorbidities, which is a limitation. Background Delirium is an acute condition affecting cognition, arousal and attention, with underlying causes that should be identified and treated properly ( 1 , 2 ). Older patients often present with delirium when acutely ill, and old age, dementia, surgery and frailty are well known risk factors for delirium ( 2 , 3 ) Delirium prevalence and incidence varies in different patient populations ( 2 ). In intensive care units up to 70% of patients develop delirium ( 2 ). A 2020 meta-analysis found that approximately 25% of older hospital admitted patients develop delirium ( 4 ). This study did however only include studies on medical and geriatric inpatients which may constrain the applicability of the estimates of occurrence to other settings, such as that of all acutely admitted patients. Delirium is often underdiagnosed ( 5 ), and is associated with negative outcomes, including longer hospitalisations, institutionalisation, and increased mortality ( 6 , 7 ). Several studies show an association between delirium and an increased risk of cognitive decline and dementia ( 6 , 8 , 9 ). Delirium also increases the cost of hospitalisation and follow-up after discharge ( 10 ). Multicomponent interventions can prevent delirium ( 11 , 12 ) and are likely cost-effective ( 13 ). International guidelines for good management of delirium in different settings include advice on treating the causes of delirium and optimising multiple factors associated with sustained delirium ( 14 , 15 ). Few guidelines exist specifically for the emergency department (ED) setting, but screening to identify high-risk patients and the use of multicomponent interventions for risk reduction and management are recommended in an umbrella review ( 16 ). Patient admissions in the emergency departments are increasing yearly, with the largest increase in the age group 67–79 years ( 17 ). The number of people living with dementia is also increasing ( 18 , 19 ). Because dementia and old age are the most important risk factors for delirium development, the prevalence of delirium in the EDs will likely increase. Delirium prevention, identification and treatment will therefore be even more important for future sustainability of the health care system, optimising use of resources and reducing costs ( 13 ). Updated estimates of delirium prevalence will likely have consequences for clinical practice, as well as implications for the distribution of healthcare resources to best treat the increasing number of ageing patients. The primary objective of this study was to estimate the delirium occurrence in an unselected cohort of acutely admitted older adults, both in the emergency department (point prevalence) and during the consecutive hospitalisation (incidence). Our secondary objective was to compare outcomes: length of stay, need for higher level of care after discharge and 9-month mortality, for patients with and without delirium. Methods 2.1 Study design Observational unselected cohort study. 2.2 Study setting Stavanger University Hospital (SUH) is a large Norwegian hospital with an emergency department (ED) with approximately 100–120 daily admissions. SUH serves a population of approximately 390 000 patients and is the sole hospital in its catchment area. About 50% of the acutely admitted patients are 65 years or above. 2.3 Study participants, inclusion and data registered We included all patients, aged 65 years or above, acutely admitted to the emergency department (ED) at Stavanger University Hospital, for 5 days, including 4 nights. The screening period lasted from Monday, 02.10.2023, 08:00 a.m. until Friday, 06.10.2023, 08:00 p.m. For patients admitted more than once during this period, only the last admission was included. The study personnel, all trained in performing the 4AT, RASS and OSLA, assisted the staff in the ED in performing the screenings. When delirium was suspected, the responsible nurse or doctor in the ED was informed. Patients admitted with life-threatening conditions, those who were expected to die during or shortly after admission were also included. The delirium screening results were documented in the patient’s electronic charts. Patients not speaking Norwegian or English were excluded unless an interpreter was available. For included patients, we analysed data on sex, age and whether the admission represented a readmission. We used the Norwegian Directorate of Health’s definition of readmission: an acute admission between 8 hours and 30 days after the last hospital discharge ( 20 ). We also registered which department the patients were admitted to, if they were discharged directly home from the ED and whether they had a known diagnosis of dementia. The National Early Warning Score 2 (NEWS2), a system for identifying clinical deterioration in patients in the ED ( 21 ), was registered at admission, as well as length of hospital stay (in whole days), and if delirium was documented as a formal diagnosis in the discharge summary. We also registered whether the admitted patients needed a higher level of care at discharge and mortality until 9 months after discharge. 2.4 Delirium screening and diagnosis Initial delirium screening was done by the 4 “A”s test (4AT)- a rapid screening test for delirium, with high sensitivity and specificity ( 22 ). If the 4AT score was > 4, the study personnel performed the Richmond Agitation Sedation Scale (RASS) ( 23 ) and the Observational Scale of Level of Arousal (OSLA) ( 24 ) to evaluate the patient’s level of agitation and arousal. No additional delirium screening was performed for the rest of the hospitalization at the wards. For all patients, retrospective chart review based on The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition’s (DSM-V) criteria for delirium ( 1 ) was performed. Two geriatricians (MNPH and AKB) retrospectively evaluated all available information from the patients charts from the hospital admission and stay to determine if the patients fulfilled a diagnosis of delirium based on DSM-V criteria. This evaluation was based on a method described previously ( 25 ), slightly modified to suit our study (Appendix 1). Patients with acute changes in cognition and disturbances in attention or awareness in the emergency department or later during hospitalisation, but not fulfilling all the DSM-V criteria, were classified as having subsyndromal delirium. Disagreements were solved through discussion with an old-age psychiatrist (AOVM). The diagnosis of delirium, by DSM-V criteria, showed high interrater reliability with a kappa of 0.92 (0.87–0.98). 2.5 Statistical methods The variables are reported as median (IQR) and number (percent). Normality was considered by the Shapiro-Wilk and Kolmogorov-Smirnov tests. Nonparametric tests were used for comparing delirium and no delirium patients with not normally distributed data. Continuous variables were analysed using Mann-Whitney U test and categorical variables were analysed using Chi square (X 2 ) statistics. Regression analyses used to compare outcomes for patients with and without delirium and correct for age, gender and NEWS2-score were performed in R version 4.3.2. Poisson regression was used to explore the length of stay, logistic regression to estimate the odds ratio for being discharged to a higher level of care, and Cox regression to test 9-month mortality. Survival curves (Kaplan Meyer plots) and figures were created using R version 4.3.2. The flowchart was created using Biorender. Interrater reliability kappa score was calculated in R-package vcd. A two-tailed p-value of < 0.05 was considered statistically significant and we used IBM SPSS Statistics version 26 software for the statistical analyses. 2.6 Ethical considerations We conducted the study in accordance with the World Medical Association Declaration of Helsinki and the Regional Committee for Medical and Health Research Ethics of Western Norway approved the study prior to its start, in line with the Norwegian Health Research act. This committee is appointed by the Norwegian Ministry of Education and Health. The participants did not need to actively consent but received written information with a possibility for reservation from participation in the study after discharge, as approved by the Regional Committee for Medical and Health Research Ethics (Western Norway; REK 424462). Patients who fulfilled inclusion criteria and died during or shortly after the study period were directly included as approved by the Regional Ethics Committee. 2.7 Patient and public involvement The project has been presented for a panel of user representatives at SESAM- Centre for Age-Related Medicine in Stavanger, and a dedicated user representative has been involved and consulted during the planning of this study. Results 3.1 Patient enrolment A total of 259 patients aged 65 years or above were admitted during the study period. After exclusions (n = 6) and withdrawals (n = 10) 243 patients remained. We excluded three additional patients with critical illness where a conclusion regarding delirium was impossible to reach due to the patient’s clinical presentation in the emergency department, leaving 92.6% (n = 240) of all the admitted patients eligible for inclusion and further analysis. Patient enrolment is shown in detail in Fig. 1 . 3.2 Delirium prevalence and incidence Delirium point prevalence was 14% in the emergency department (ED), as 33 of 240 patients fulfilled DSM-V criteria for delirium. 17 of the 207 patients that did not have delirium in the ED developed delirium during the remaining hospital stay. The incidence of delirium development later during the hospitalisation was thus 8% (n = 17), and 3% (n = 7) fulfilled the criteria for a subsyndromal delirium. The total occurrence of delirium, both prevalent og incident, during the hospitalization was 21% (50 of 240 patients). 3.3 Study population characteristics Population characteristics are shown in Table 1 . The median age of the patients with delirium was significantly higher than that of the patients without delirium (82 vs 76 years, p < 0.001). 54% (n = 27) of patients with delirium were female compared to 41% (n = 75) of patients without delirium. 94% of patients with delirium were 70 years of age or older. Median NEWS-score in the ED was 3 for patients with delirium compared to 1 for patients without delirium (p = 0.004). 14% (n = 7) of the patients with delirium had a known diagnosis of dementia, compared to 1.6% (n = 3) for patients without delirium (p = 0.001). This hospital admission was a readmission for 23% of all the patients. Readmissions were more prevalent in patients with delirium compared to patients with no delirium (42 vs 18%, p < 0.001, see Table 2 ). Overall, patients were mostly admitted to the department of internal medicine 33% (n = 79), orthopaedic surgery 7% (n = 17) and surgical departments 13% (n = 31). Delirium patients showed a similar distribution regarding which departments they were admitted to. Table 1 Population characteristics and comparisons for acutely admitted patients > 65 years and with and without delirium by DSM-V criteria during the hospitalization. Characteristic Overall N = 233 1 Delirium anytime during hospitalization N = 50 1 No delirium during hospitalization N = 183 1 p-value 2 Age 77 (72, 84) 82 (76, 88) 76 (70, 83) < 0.001 Sex 0.10 Male 131(56%) 23(46%) 108(59%) Female 102(44%) 27(54%) 75(41%) NEWS score ED 2.00 (0.00,3.00) 3.00 (0.50, 5.50) 1.00 (0.00, 3.00) 0.004 Unknown 47 ( 20 ) 7( 14 ) 40( 22 ) Known dementia* 0.001 No 223(96%) 43(86%) 180(98%) Yes 10(4.3%) 7(14%) 3(1.6%) Is the admission a readmission? < 0.001 No 179(77%) 29(58%) 150(82%) Yes 54(23%) 21(42%) 33(18%) Delirium diagnosis at discharge? 0.002 No 229(98%) 46(92%) 183(100%) Yes 4(1.7%) 4(8.0%) 0(0%) Discharged home from ED? < 0.001 No 174(75%) 48(96%) 126(69%) Yes 59(25%) 2(4.0%) 57(31%) 1 Median (IQR); n(%) 2 Mann-Whitney u test; Pearson’s Chi-squared test; Fisher’s exact test *Dementia was based on chart review from all the information in the patient’s hospital records related to the hospital admission in the study period to see if they had an documented diagnosis of dementia. 3.4 Delirium screening and diagnosis at discharge Of all patients eligible for inclusion 96.7% (232 of 240) were screened by 4AT in the emergency department, and 70% (23 of 33) of the patients with delirium had a 4AT-score equal to or above 4, compared to 1% (2 of 207) of the patients with no delirium in the ED (p < 0.001). A total of 8% (n = 4) of patients with delirium by DSM-V criteria, both in the ED and during the consecutive hospitalisation, had a documented diagnosis of delirium at discharge from the hospital. 3.5 Outcomes A comparison of outcomes for patients with and without delirium is visualized in Table 2 . Patients with delirium were more often discharged to a higher level of care, 48% vs 20% compared to patients without delirium, but when corrected for age, gender and severity of acute illness by NEWS2-score the difference was not statistically significant (p = 0.156). 31% of acutely admitted patients > 65 years without delirium were discharged directly home from the ED vs 4% (p < 0.001) of patients with delirium. The length of hospital stay in whole days was significantly longer in patients with delirium (4.0 days, CI 2-9.5), compared to patients without delirium (2.0 days, CI 0–4, p 65 years, with and without delirium during their hospitalization: higher level of care, length of hospital stay and cumulative 9-month mortality, corrected for age and severity of acute illness by The National Early Warning Score. Overall, N = 233 1 Delirium anytime during hospitalization, N = 50 1 No delirium during hospitalization, N = 183 1 Estimates (95% CI) p-value 2 Higher level of care after hospitalization* 21 (48) 37 ( 20 ) OR 1.83 (0.79; 4.22) 0.156 Length of hospital stay* 4.0 (2.0-9.5) 2.0 (0.0–4.0) OR 1.72 (1.48; 2.0) < 0.001 Cumulative 9-month mortality * 26 (52) 25 ( 14 ) HR 2.90 (1.50; 5.62) 0.002 1 Median (IQR); n(%) 2 Logistic regression; Poisson regression; Cox regression *NEWS score is missing for n=50 patients. For all patients included in this study, the 9-month mortality was 21%. Cumulative 9-month mortality was 52% (n = 26) for patients with delirium, compared to 14% (n = 25) for patients without delirium (p = 0.002, HR 2.90 (1.50;5.62)), adjusted for age, gender and NEWS-2 score. Figure 2 shows Kaplan Meyer plots comparing days to death in patients with and without delirium during the hospitalization, corrected for age, gender and NEWS2-score, showing a significant difference in cumulative 9-month mortality between patients with and without delirium. Discussion This study found delirium to be common in acutely admitted older adults, with a point prevalence of 14% in the emergency department. The incidence was 8% during the rest of the hospitalisation for patients without delirium in the ED, giving a total occurrence of 21%. This is in line with estimates from a previous meta-analysis of published estimates of delirium occurrence in medical and geriatric inpatients over decades, showing an overall occurrence of 23% ( 4 ). Our study design allowed for an unselected inclusion of all acutely admitted patients which is important as many previous studies have examined specific cohorts of patients, such as medical geriatric patients ( 26 ), oncological patients ( 27 ), patients receiving non-invasive positive pressure ventilation ( 28 ), acute medical patients ( 29 ), or intensive care patients ( 30 ). In later years the “delirium day” studies have aimed to estimate delirium point prevalence of acutely admitted patients, but with varying percentages of all acutely admitted patients included- such as 56% in a Norwegian study of medical and surgical wards ( 31 ) and 84% in a study across 108 acute and 12 rehabilitation wards in Italy ( 32 ). It is a potential challenge in delirium studies that systematic assessments of capacity for consent, may lead to the exclusion of patients with delirium ( 33 ). We included a very high percentage (92.6%) of all the acutely admitted patients in the study period without obtaining consent but gave the patients an opportunity for reservation, as approved by the ethical committee. A large international study conducted by the World Delirium Awareness Day team reported on delirium prevalence at two specific time points during one day in 2023 ( 34 ). In this study, 2502 wards or units started, yet only 66.5% (n = 1664 wards) were analysed, meaning that even though the final number of patients was high the estimates of occurrence may have been biased. Ideally, delirium prevalence studies should include large numbers of patients and in addition include as many of the eligible patients as possible. The cut off for inclusion was > 65 years in our study, and the median age of the patients included was 77 years. The patients with delirium were with a median age of 82 years significantly older than the non-delirious patients. Knowing that delirium risk is increased with higher age, the estimates would be expected to increase if we set the inclusion age higher, e.g. at > 75 years. We chose 65 years as this is a commonly used definition of older adults, used among others by the United States National Institute of Aging ( 35 ). Our finding that 94% of the patients with delirium were > 70 years is relevant in terms of which patient groups should be the focus of delirium identification. The National Institute for Health and Care Excellence guidelines highlight that patients aged > 65 years are at an increased risk of delirium development ( 15 ). Yet, delirium identification in all admitted patients in this age group is resource demanding and a specification of which patients to prioritise for screening could be useful. Interestingly, for patients with delirium the current admission was a readmission for 42% compared to 18% for patients without a delirium. Potential reasons could be a higher burden of comorbidity or frailty in delirium patients. This finding is still relevant information for health care personnel working in the emergency departments, particularly if resources are scant and not sufficient to perform delirium identification in all patients > 65 years. The high screening percentage of 96.7% in our study period is not indicative of the general screening rate of delirium in our emergency department. In our study only 70% of the patients who fulfilled a delirium diagnosis by DSM-V criteria had a 4AT score of 4 or above, which is low considering the diagnostic accuracy of the 4AT described previously ( 22 ). Our study has a unselected design meaning that 4AT could be less sensitive in this setting, which is supported by the findings of a sensitivity of 4AT of 76% in a randomized study performed in a similar setting ( 36 ). We found that delirium patients are admitted to most of the departments examined in our study, highlighting the need for delirium knowledge and awareness throughout the hospital. 3% of the patients presented with subsyndromal delirium (SSD) during the hospitalization. We did not find a higher 9-month mortality in this group, which could be explained by a low number of patients. SSD is nonetheless relevant as several previous studies have shown that patients with SSD have an increased risk of negative outcomes ( 37 , 38 ). Only 8% of patients with delirium had a formal diagnosis documented in their electronic chart at discharge, which is low, but expected given results from other studies ( 5 , 39 ). This number stands in contrast to the identified delirium occurrence in our hospital and could indicate that most cases of delirium are never identified and thus not treated according to recommendations for good practice ( 14 , 15 ). Yet, it is uplifting to see that only 2 (4%) of patients with delirium were discharged directly home from the ED, indicating that the health care personnel have been aware of these patients and treated them in hospital. The increased risk of delirium development in dementia is well established ( 2 , 40 ), and the patients with dementia had, as expected, a significantly higher occurrence of delirium in our study. The National Early Warning Score 2 (NEWS2) was significantly higher for delirium patients in our study, most likely indicating increased severity of the presenting illness in delirious patients. We found, in line with previous studies ( 6 , 7 ), that length of hospital stay and mortality was significantly associated with delirium. Former studies have found 4AT > 4 to be a strong predictor of death ( 41 ). We did not find a statistically significant difference in level of care after discharge between patients with and without delirium when correcting for age and NEWS, which could be because delirium was not diagnosed and acknowledged. This finding was not in line with a previous meta-analysis which found delirium to be associated with an increased risk of institutionalisation [6]. A large 2025 study of more than 18000 hip fracture patients found delirium to be associated with a lower likelihood of returning home within 30 days ( 42 ). Strengths and limitations A strength of our study is the high proportion of eligible patients included, as more than 92% of the target population for the study was included, which is rather high compared to similar studies. Our high inclusion rate is a strength in providing an accurate estimate of delirium prevalence and incidence. Stavanger University Hospital is the only hospital in our catchment area, meaning that hospitalised patients with delirium are not admitted elsewhere, which could be the case in other countries and cities where several hospitals share a specified catchment area. We have based our formal delirium diagnosis on The Diagnostic and Statistical Manual of Mental Disorders, Fifth Editions criteria ( 1 ), conducted by two independent geriatricians experienced in delirium diagnosis. This is a strength, because although the sensitivity and specificity of the 4As test is high ( 22 ), it does not represent a formal delirium diagnosis. For some patients an increased score on the 4As may not represent a delirium, particularly in patients with existing cognitive decline and dementia, where a formal diagnosis of delirium can be challenging ( 40 ). It is well known that delirium estimates differ based on the diagnostic criteria used, with DMS-IV showing higher estimates than DSM-V ( 4 ), which was used in our study. Our chart-based delirium diagnosis is a potential limitation compared to a more comprehensive diagnostic process in the clinic, yet patients were screened and assessed for delirium in the ED in addition to the chart-based method. It is also a strength that we estimate both a point prevalence and an incidence for delirium, as many studies in recent years provide only a delirium point prevalence ( 31 , 32 , 34 ). No systematical daily delirium screening was conducted after the emergency department, which means that the retrospective diagnosis of delirium in the hospital wards is based on the notes in the medical record, which is a limitation. Systematically considering delirium daily throughout the hospitalisation could possibly have identified more patients with a hypoactive delirium and thus increased the estimates of delirium incidence. This study also has limitations: it was conducted in a single hospital, and only included patients for 5 days and 4 nights, which is a short period, and did not include the weekend. This could have led to a selection bias. We had to balance the need for a high inclusion rate to provide an accurate estimate of prevalence with the secondary aims of examining outcomes for delirium patients. It would be relevant to adjust our outcomes for frailty as well as for comorbidity to explore whether the negative outcomes observed in delirium patients might indeed be caused by delirium itself. To get a high inclusion rate, we were given approval from the ethic committee to collect information without obtaining consent from the participants first but were limited to collecting only some predefined data. Our primary aim was to investigate the occurrence of delirium, and we thus chose to prioritize this in the design of our study. Conclusions We found delirium to be common, with a total occurrence of 21% among hospitalised unselected older adults > 65 years acutely admitted in the study period. Only 8% of those with delirium had a formal delirium diagnosis documented in the discharge summaries. Patients with delirium showed significantly increased length of stay and 9-month mortality. As the population ages and the number of people living with dementia increases, updated estimates of delirium prevalence in unselected cohorts are important to increase the attention and focus on delirium. Delirium prevention, identification and management are key aspects of a sustainable health care system facing an increasing proportion of older adults with multifaceted health issues and varying levels of cognitive dysfunction. Future studies should include a larger number of patients, diagnose delirium by verified diagnostic criteria and assess as high a percentage of all eligible patients as possible to provide accurate and non-biased estimates of delirium prevalence. Repeated cross-sectional studies could be relevant to examine the change of delirium prevalence over time. Abbreviations 4AT: The 4 “A” s test DSM-V: The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition ED: Emergency department IQR: Inter quartile range NEWS: National Early Warning Score OSLA: Observational Scale of Level of Arousal RASS: Richmond Agitation Sedation Scale SESAM: Centre for Age-Related Medicine SUH: Stavanger University Hospital NIH: National Institute of Aging NICE: National Institute for Health and Care Excellence Declarations Declaration of interest: the authors all declare no conflict of interest. Supplementary figure showing a distribution of which departments patients with delirium were admitted to. Ethical approval and consent to participate We conducted the study in accordance with the World Medical Association Declaration of Helsinki and the Regional Committee for Medical and Health Research Ethics of Western Norway approved the study prior to its start, in line with the Norwegian legislation- the research ethics act and the Health Research act. This committee is appointed by the Norwegian Ministry of Education and Health. The patients received written information with a possibility for reservation from participation in the study after discharge, as approved by the Regional Committee for Medical and Health Research Ethics (Western Norway; REK 424462). Patients who fulfilled inclusion criteria and died during or shortly after the study period were directly included as approved by the Regional Ethics Committee. The patients did not need to consent to participate in the study, this was approved by the Regional Committee for Medical and Health Research Ethics. Consent for publication Not applicable. Availability of data and materials The dataset analyzed during the current study can upon request to the first author be made available, but only after application to and approval by The Regional Ethical Committee. Competing interests The authors declare that they have no competing interests. Funding The study was funded by the Norwegian Health Association and The Western Norway Regional Health Authorities (Grant numbers F-12592 and F12614), and by Helse Stavanger by a grant from the Psychiatric Division. Authors contributions MNPH contributed to the concept, study design, collection of data, statistical analysis and drafted the manuscript. HS contributed to the concept, study design, collection of data and revised the manuscript. HBH contributed to the study design, statistical analysis and revised the manuscript. AOVM contributed to the study design and revised the manuscript. AD contributed to the study design and revised the manuscript. AS contributed to the study design, collection of data and revised the manuscript. RTWO contributed to the study design, collection of data and revised the manuscript. LOW contributed to the study design and revised the manuscript. DA contributed to the concept, study design and revised the manuscript. AKB contributed to the concept, study design and revised the manuscript. All authors read and approved the final manuscript. Acknowledgments We thank the research nurses and staff of the emergency department at Stavanger University Hospital for their valuable contributions to this study. References American Psychiatric Association.The Diagnostic and Statistical Manual of Mental Disorders: DSM-V. 5th edition. Washington, D.C:: American Psychiatric Association.; 2013. Wilson JE, Mart MF, Cunningham C, Shehabi Y, Girard TD, MacLullich AMJ, et al. Delirium. Nat Rev Dis Primers. 2020;6(1):90. Deiner SG, Marcantonio ER, Trivedi S, Inouye SK, Travison TG, Schmitt EM, et al. Comparison of the frailty index and frailty phenotype and their associations with postoperative delirium incidence and severity. J Am Geriatr Soc. 2024;72(6):1781-92. Gibb K, Seeley A, Quinn T, Siddiqi N, Shenkin S, Rockwood K, Davis D. 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Akunne A, Murthy L, Young J. Cost-effectiveness of multi-component interventions to prevent delirium in older people admitted to medical wards. Age Ageing. 2012;41(3):285-91. (SIGN) SIGN. Risk reduction and management of delirium. Edinburgh: SIGN; 2019. 2019 [07.10.2024]. Available from: https://www.sign.ac.uk/media/1423/sign157.pdf. National Institute for Health and Care Excellence (NICE). Delirium: prevention, diagnosis and management in hospital and long-term care: National Institute for Health and Care Excellence; 2010 [updated 18.01.2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553009/. Filiatreault S, Grimshaw JM, Kreindler SA, Chochinov A, Linton J, Chatterjee R, et al. A critical appraisal and recommendation synthesis of delirium clinical practice guidelines relevant to the care of older adults in the emergency department: An umbrella review. J Eval Clin Pract. 2023;29(6):1039-53. Nummedal MA, Markussen DL, Næss LE, Laugsand LE, Bjørnsen LP. Patient influx to emergency departments at two Norwegian university hospitals from 2012-21. Tidsskr Nor Laegeforen. 2024;144(8). Gjøra L, Strand BH, Bergh S, Borza T, Brækhus A, Engedal K, et al. Current and Future Prevalence Estimates of Mild Cognitive Impairment, Dementia, and Its Subtypes in a Population-Based Sample of People 70 Years and Older in Norway: The HUNT Study. J Alzheimers Dis. 2021;79(3):1213-26. Estimation of the global prevalence of dementia in 2019 and forecasted prevalence in 2050: an analysis for the Global Burden of Disease Study 2019. Lancet Public Health. 2022;7(2):e105-e25. Healths NDo. Reinnleggelse blant eldre 30 dager etter utskrivning [12.03.2025]. Available from: https://www.helsedirektoratet.no/statistikk/kvalitetsindikatorer/behandling-av-sykdom-og-overlevelse/reinnleggelse-blant-eldre-30-dager-etter-utskrivning#:~:text=Reinnleggelse%20er%20definert%20som%20en,en%20utskrivning%20fra%20et%20sykehus. Physicians RCO. National Early Warning Score (NEWS) 2 Standardising the assessment of acute-illness severity in the NHS. 2017 [05.05.2025]. Available from: https://www.rcp.ac.uk/media/a4ibkkbf/news2-final-report_0_0.pdf. Tieges Z, Maclullich AMJ, Anand A, Brookes C, Cassarino M, O'Connor M, et al. Diagnostic accuracy of the 4AT for delirium detection in older adults: systematic review and meta-analysis. Age Ageing. 2021;50(3):733-43. Sessler CN, Gosnell MS, Grap MJ, Brophy GM, O'Neal PV, Keane KA, et al. The Richmond Agitation-Sedation Scale: validity and reliability in adult intensive care unit patients. Am J Respir Crit Care Med. 2002;166(10):1338-44. Tieges Z, McGrath A, Hall RJ, Maclullich AM. Abnormal level of arousal as a predictor of delirium and inattention: an exploratory study. Am J Geriatr Psychiatry. 2013;21(12):1244-53. Watne LO, Pollmann CT, Neerland BE, Quist-Paulsen E, Halaas NB, Idland AV, et al. Cerebrospinal fluid quinolinic acid is strongly associated with delirium and mortality in hip-fracture patients. Journal of Clinical Investigation. 2023;133(2). Evensen S, Saltvedt I, Lydersen S, Wyller TB, Taraldsen K, Sletvold O. Environmental factors and risk of delirium in geriatric patients: an observational study. BMC Geriatr. 2018;18(1):282. Grandahl MG, Nielsen SE, Koerner EA, Schultz HH, Arnfred SM. Prevalence of delirium among patients at a cancer ward: Clinical risk factors and prediction by bedside cognitive tests. Nord J Psychiatry. 2016;70(6):413-7. Chan KY, Cheng LS, Mak IW, Ng SW, Yiu MG, Chu CM. Delirium is a Strong Predictor of Mortality in Patients Receiving Non-invasive Positive Pressure Ventilation. Lung. 2017;195(1):115-25. Pendlebury ST, Lovett NG, Smith SC, Dutta N, Bendon C, Lloyd-Lavery A, et al. Observational, longitudinal study of delirium in consecutive unselected acute medical admissions: age-specific rates and associated factors, mortality and re-admission. BMJ Open. 2015;5(11):e007808. Krewulak KD, Stelfox HT, Leigh JP, Ely EW, Fiest KM. Incidence and Prevalence of Delirium Subtypes in an Adult ICU: A Systematic Review and Meta-Analysis. Crit Care Med. 2018;46(12):2029-35. Instenes I, Eide LSP, Andersen H, Fålun N, Pettersen T, Ranhoff AH, et al. Detection of delirium in older patients-A point prevalence study in surgical and non-surgical hospital wards. Scand J Caring Sci. 2024;38(3):579-88. Bellelli G, Morandi A, Di Santo SG, Mazzone A, Cherubini A, Mossello E, et al. "Delirium Day": a nationwide point prevalence study of delirium in older hospitalized patients using an easy standardized diagnostic tool. BMC Medicine. 2016;14:106. Adamis D, Martin FC, Treloar A, Macdonald AJ. Capacity, consent, and selection bias in a study of delirium. J Med Ethics. 2005;31(3):137-43. Lindroth H, Liu K, Szalacha L, Ashkenazy S, Bellelli G, van den Boogaard M, et al. World delirium awareness and quality survey in 2023-a worldwide point prevalence study. Age Ageing. 2024;53(11). Aging NIo. Age 2025 [Available from: https://www.nih.gov/nih-style-guide/age#:~:text=The%20National%20Institute%20on%20Aging,these%20terms%2C%20ask%20for%20specifics. Shenkin SD, Fox C, Godfrey M, Siddiqi N, Goodacre S, Young J, et al. Delirium detection in older acute medical inpatients: a multicentre prospective comparative diagnostic test accuracy study of the 4AT and the confusion assessment method. BMC Med. 2019;17(1):138. Shim J, DePalma G, Sands LP, Leung JM. Prognostic Significance of Postoperative Subsyndromal Delirium. Psychosomatics. 2015;56(6):644-51. Cole M, McCusker J, Dendukuri N, Han L. The prognostic significance of subsyndromal delirium in elderly medical inpatients. J Am Geriatr Soc. 2003;51(6):754-60. Ibitoye T, So S, Shenkin SD, Anand A, Reed MJ, Vardy E, et al. Delirium is under-reported in discharge summaries and in hospital administrative systems: a systematic review. Delirium (Bielef). 2023;2023:74541. Fong TG, Inouye SK. The inter-relationship between delirium and dementia: the importance of delirium prevention. Nature Reviews Neurology. 2022;18(10):579-96. Anand A, Cheng M, Ibitoye T, Maclullich AMJ, Vardy E. Positive scores on the 4AT delirium assessment tool at hospital admission are linked to mortality, length of stay and home time: two-centre study of 82,770 emergency admissions. Age Ageing. 2022;51(3). Penfold RS, Farrow L, Hall AJ, Clement ND, Ward K, Donaldson L, et al. Delirium on presentation with a hip fracture is associated with adverse outcomes : a multicentre observational study of 18,040 patients using national clinical registry data. Bone Joint J. 2025;107-b(4):470-8. Appendix 1 Appendix 1 is not available with this version. Additional Declarations No competing interests reported. Supplementary Files Supplementaryfigure.docx RevisedDSMVdiagnostictable.pdf Cite Share Download PDF Status: Published Journal Publication published 19 Dec, 2025 Read the published version in BMC Geriatrics → Version 1 posted Editorial decision: Revision requested 30 Oct, 2025 Reviews received at journal 15 Oct, 2025 Reviewers agreed at journal 15 Oct, 2025 Reviewers agreed at journal 09 Sep, 2025 Reviews received at journal 02 Sep, 2025 Reviewers agreed at journal 28 Aug, 2025 Reviewers agreed at journal 06 Aug, 2025 Reviewers invited by journal 06 Aug, 2025 Editor assigned by journal 29 Jul, 2025 Editor invited by journal 29 Jul, 2025 Submission checks completed at journal 29 Jul, 2025 First submitted to journal 29 Jul, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Hospital","correspondingAuthor":false,"prefix":"","firstName":"Hogne","middleName":"","lastName":"Soennesyn","suffix":""},{"id":497965434,"identity":"cdb75608-98d9-45fa-a2dd-8c3c731fc7df","order_by":2,"name":"Hanne Brit Hetland","email":"","orcid":"","institution":"Stavanger University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Hanne","middleName":"Brit","lastName":"Hetland","suffix":""},{"id":497965435,"identity":"72685132-4baf-42b6-b21e-dd4af2be0ae5","order_by":3,"name":"Audun Osland Vik-Mo","email":"","orcid":"","institution":"University of Bergen","correspondingAuthor":false,"prefix":"","firstName":"Audun","middleName":"Osland","lastName":"Vik-Mo","suffix":""},{"id":497965437,"identity":"6728d8a4-ae89-4ebf-a6d7-52dd5392c5b0","order_by":4,"name":"Ane Djuv","email":"","orcid":"","institution":"University of Bergen","correspondingAuthor":false,"prefix":"","firstName":"Ane","middleName":"","lastName":"Djuv","suffix":""},{"id":497965439,"identity":"a9bc9954-824b-4761-82c8-2826555e4e09","order_by":5,"name":"Anita Sunde","email":"","orcid":"","institution":"University of Bergen","correspondingAuthor":false,"prefix":"","firstName":"Anita","middleName":"","lastName":"Sunde","suffix":""},{"id":497965442,"identity":"7c0aabd0-5318-461d-91f2-050d0cdca794","order_by":6,"name":"Rune Tord Wathne Oftedal","email":"","orcid":"","institution":"Stavanger University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Rune","middleName":"Tord Wathne","lastName":"Oftedal","suffix":""},{"id":497965443,"identity":"54f1c8b4-f120-4384-9064-e0f2edd7914d","order_by":7,"name":"Leiv Otto Watne","email":"","orcid":"","institution":"University of Oslo","correspondingAuthor":false,"prefix":"","firstName":"Leiv","middleName":"Otto","lastName":"Watne","suffix":""},{"id":497965444,"identity":"872dd9f0-b71b-48cd-b242-11872e9b3c90","order_by":8,"name":"Dag Aarsland","email":"","orcid":"","institution":"King’s College London","correspondingAuthor":false,"prefix":"","firstName":"Dag","middleName":"","lastName":"Aarsland","suffix":""},{"id":497965445,"identity":"5f165fa3-df71-4790-9eac-cdff1532c315","order_by":9,"name":"Anne Katrine Bergland","email":"","orcid":"","institution":"University of Bergen","correspondingAuthor":false,"prefix":"","firstName":"Anne","middleName":"Katrine","lastName":"Bergland","suffix":""}],"badges":[],"createdAt":"2025-07-22 08:38:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7184588/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7184588/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12877-025-06903-8","type":"published","date":"2025-12-19T15:58:13+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":88897998,"identity":"7dc38f27-3957-4798-809c-8481cd5be613","added_by":"auto","created_at":"2025-08-12 13:19:12","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":295852,"visible":true,"origin":"","legend":"\u003cp\u003eFlow chart presenting an overview of enrolment of acutely admitted patients to the emergency department in the study period, and the conclusion regarding delirium diagnosis according to The Diagnostic and Statistical Manual of Mental Disorders, Fifth Editions criteria.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7184588/v1/6a767c7f80aaa66710ce904e.png"},{"id":88899247,"identity":"72c0c66e-77f1-4ee2-9104-d37ec3ba3752","added_by":"auto","created_at":"2025-08-12 13:27:12","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":187350,"visible":true,"origin":"","legend":"\u003cp\u003eKaplan Meyer plots, comparing days to death in A) acutely admitted patients aged \u003cu\u003e\u0026gt;\u003c/u\u003e65 years, with and without delirium during the hospitalization, corrected for age, gender and NEWS2-score, showing a significant difference in cumulative 9-month mortality. B) the same patients divided into delirium subgroups; delirium present in the emergency department, delirium developed later during hospitalization, subsyndromal delirium during hospitalization and no delirium during hospitalization showing that the difference is mainly due to the patients with delirium prevalent in the emergency department.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7184588/v1/ee99028fee67f65fd51d3a99.png"},{"id":98814141,"identity":"5aa15940-3e7b-48ed-b0ac-6987a459e2a0","added_by":"auto","created_at":"2025-12-22 16:11:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1408488,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7184588/v1/15e86236-37f2-4ad5-bec4-1c2654db852d.pdf"},{"id":88897070,"identity":"ceafe446-69e3-4bb6-97f2-3a8bae656b93","added_by":"auto","created_at":"2025-08-12 13:11:12","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":230397,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryfigure.docx","url":"https://assets-eu.researchsquare.com/files/rs-7184588/v1/da8be0121f1a3f62a230e1a1.docx"},{"id":88898000,"identity":"4d9157d2-0e2a-4d45-be57-caf8fc231e02","added_by":"auto","created_at":"2025-08-12 13:19:13","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":421504,"visible":true,"origin":"","legend":"","description":"","filename":"RevisedDSMVdiagnostictable.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7184588/v1/cc0ac8f73c37c695a49e2b3e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Delirium prevalence and incidence in acutely admitted older patients: an observational cohort study","fulltext":[{"header":"Strengths and limitations of this study","content":"\u003cul\u003e\n \u003cli\u003eWe included 92% of all acutely admitted patients in the study period, which is high compared to similar studies and a strength in providing a precise and updated estimate of delirium occurrence.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eWe registered both delirium prevalence in the emergency department and incidence during the rest of the hospitalisation.\u003c/li\u003e\n \u003cli\u003eDelirium assessment was done systematically and independently by two geriatricians, with high interrater reliability, based on The Diagnostic and Statistical Manual of Mental Disorders, Fifth Editions criteria.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eWe compared outcomes for patients with and without delirium but without data on comorbidities, which is a limitation. \u0026nbsp;\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"Background","content":"\u003cp\u003eDelirium is an acute condition affecting cognition, arousal and attention, with underlying causes that should be identified and treated properly (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). Older patients often present with delirium when acutely ill, and old age, dementia, surgery and frailty are well known risk factors for delirium (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eDelirium prevalence and incidence varies in different patient populations (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). In intensive care units up to 70% of patients develop delirium (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). A 2020 meta-analysis found that approximately 25% of older hospital admitted patients develop delirium (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). This study did however only include studies on medical and geriatric inpatients which may constrain the applicability of the estimates of occurrence to other settings, such as that of all acutely admitted patients. Delirium is often underdiagnosed (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e), and is associated with negative outcomes, including longer hospitalisations, institutionalisation, and increased mortality (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). Several studies show an association between delirium and an increased risk of cognitive decline and dementia (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). Delirium also increases the cost of hospitalisation and follow-up after discharge (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). Multicomponent interventions can prevent delirium (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e) and are likely cost-effective (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). International guidelines for good management of delirium in different settings include advice on treating the causes of delirium and optimising multiple factors associated with sustained delirium (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). Few guidelines exist specifically for the emergency department (ED) setting, but screening to identify high-risk patients and the use of multicomponent interventions for risk reduction and management are recommended in an umbrella review (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e).\u003c/p\u003e\u003cp\u003ePatient admissions in the emergency departments are increasing yearly, with the largest increase in the age group 67\u0026ndash;79 years (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). The number of people living with dementia is also increasing (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). Because dementia and old age are the most important risk factors for delirium development, the prevalence of delirium in the EDs will likely increase. Delirium prevention, identification and treatment will therefore be even more important for future sustainability of the health care system, optimising use of resources and reducing costs (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). Updated estimates of delirium prevalence will likely have consequences for clinical practice, as well as implications for the distribution of healthcare resources to best treat the increasing number of ageing patients.\u003c/p\u003e\u003cp\u003eThe primary objective of this study was to estimate the delirium occurrence in an unselected cohort of acutely admitted older adults, both in the emergency department (point prevalence) and during the consecutive hospitalisation (incidence). Our secondary objective was to compare outcomes: length of stay, need for higher level of care after discharge and 9-month mortality, for patients with and without delirium.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Study design\u003c/h2\u003e\u003cp\u003eObservational unselected cohort study.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Study setting\u003c/h2\u003e\u003cp\u003eStavanger University Hospital (SUH) is a large Norwegian hospital with an emergency department (ED) with approximately 100\u0026ndash;120 daily admissions. SUH serves a population of approximately 390 000 patients and is the sole hospital in its catchment area. About 50% of the acutely admitted patients are 65 years or above.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Study participants, inclusion and data registered\u003c/h2\u003e\u003cp\u003eWe included all patients, aged 65 years or above, acutely admitted to the emergency department (ED) at Stavanger University Hospital, for 5 days, including 4 nights. The screening period lasted from Monday, 02.10.2023, 08:00 a.m. until Friday, 06.10.2023, 08:00 p.m. For patients admitted more than once during this period, only the last admission was included. The study personnel, all trained in performing the 4AT, RASS and OSLA, assisted the staff in the ED in performing the screenings. When delirium was suspected, the responsible nurse or doctor in the ED was informed. Patients admitted with life-threatening conditions, those who were expected to die during or shortly after admission were also included. The delirium screening results were documented in the patient\u0026rsquo;s electronic charts. Patients not speaking Norwegian or English were excluded unless an interpreter was available. For included patients, we analysed data on sex, age and whether the admission represented a readmission. We used the Norwegian Directorate of Health\u0026rsquo;s definition of readmission: an acute admission between 8 hours and 30 days after the last hospital discharge (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e). We also registered which department the patients were admitted to, if they were discharged directly home from the ED and whether they had a known diagnosis of dementia. The National Early Warning Score 2 (NEWS2), a system for identifying clinical deterioration in patients in the ED (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e), was registered at admission, as well as length of hospital stay (in whole days), and if delirium was documented as a formal diagnosis in the discharge summary. We also registered whether the admitted patients needed a higher level of care at discharge and mortality until 9 months after discharge.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Delirium screening and diagnosis\u003c/h2\u003e\u003cp\u003eInitial delirium screening was done by the 4 \u0026ldquo;A\u0026rdquo;s test (4AT)- a rapid screening test for delirium, with high sensitivity and specificity (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). If the 4AT score was \u0026gt;\u0026thinsp;4, the study personnel performed the Richmond Agitation Sedation Scale (RASS) (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e) and the Observational Scale of Level of Arousal (OSLA) (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e) to evaluate the patient\u0026rsquo;s level of agitation and arousal. No additional delirium screening was performed for the rest of the hospitalization at the wards. For all patients, retrospective chart review based on The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition\u0026rsquo;s (DSM-V) criteria for delirium (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) was performed. Two geriatricians (MNPH and AKB) retrospectively evaluated all available information from the patients charts from the hospital admission and stay to determine if the patients fulfilled a diagnosis of delirium based on DSM-V criteria. This evaluation was based on a method described previously (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e), slightly modified to suit our study (Appendix 1). Patients with acute changes in cognition and disturbances in attention or awareness in the emergency department or later during hospitalisation, but not fulfilling all the DSM-V criteria, were classified as having subsyndromal delirium. Disagreements were solved through discussion with an old-age psychiatrist (AOVM). The diagnosis of delirium, by DSM-V criteria, showed high interrater reliability with a kappa of 0.92 (0.87\u0026ndash;0.98).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5 Statistical methods\u003c/h2\u003e\u003cp\u003eThe variables are reported as median (IQR) and number (percent). Normality was considered by the Shapiro-Wilk and Kolmogorov-Smirnov tests. Nonparametric tests were used for comparing delirium and no delirium patients with not normally distributed data. Continuous variables were analysed using Mann-Whitney U test and categorical variables were analysed using Chi square (X\u003csup\u003e2\u003c/sup\u003e) statistics. Regression analyses used to compare outcomes for patients with and without delirium and correct for age, gender and NEWS2-score were performed in R version 4.3.2. Poisson regression was used to explore the length of stay, logistic regression to estimate the odds ratio for being discharged to a higher level of care, and Cox regression to test 9-month mortality. Survival curves (Kaplan Meyer plots) and figures were created using R version 4.3.2. The flowchart was created using Biorender. Interrater reliability kappa score was calculated in R-package vcd. A two-tailed p-value of \u0026lt;\u0026thinsp;0.05 was considered statistically significant and we used IBM SPSS Statistics version 26 software for the statistical analyses.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6 Ethical considerations\u003c/h2\u003e\u003cp\u003e We conducted the study in accordance with the World Medical Association Declaration of Helsinki and the Regional Committee for Medical and Health Research Ethics of Western Norway approved the study prior to its start, in line with the Norwegian Health Research act. This committee is appointed by the Norwegian Ministry of Education and Health. The participants did not need to actively consent but received written information with a possibility for reservation from participation in the study after discharge, as approved by the Regional Committee for Medical and Health Research Ethics (Western Norway; REK 424462). Patients who fulfilled inclusion criteria and died during or shortly after the study period were directly included as approved by the Regional Ethics Committee.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.7 Patient and public involvement\u003c/h2\u003e\u003cp\u003eThe project has been presented for a panel of user representatives at SESAM- Centre for Age-Related Medicine in Stavanger, and a dedicated user representative has been involved and consulted during the planning of this study.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Patient enrolment\u003c/h2\u003e\u003cp\u003eA total of 259 patients aged 65 years or above were admitted during the study period. After exclusions (n\u0026thinsp;=\u0026thinsp;6) and withdrawals (n\u0026thinsp;=\u0026thinsp;10) 243 patients remained. We excluded three additional patients with critical illness where a conclusion regarding delirium was impossible to reach due to the patient\u0026rsquo;s clinical presentation in the emergency department, leaving 92.6% (n\u0026thinsp;=\u0026thinsp;240) of all the admitted patients eligible for inclusion and further analysis. Patient enrolment is shown in detail in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Delirium prevalence and incidence\u003c/h2\u003e\u003cp\u003eDelirium point prevalence was 14% in the emergency department (ED), as 33 of 240 patients fulfilled DSM-V criteria for delirium. 17 of the 207 patients that did not have delirium in the ED developed delirium during the remaining hospital stay. The incidence of delirium development later during the hospitalisation was thus 8% (n\u0026thinsp;=\u0026thinsp;17), and 3% (n\u0026thinsp;=\u0026thinsp;7) fulfilled the criteria for a subsyndromal delirium. The total occurrence of delirium, both prevalent og incident, during the hospitalization was 21% (50 of 240 patients).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Study population characteristics\u003c/h2\u003e\u003cp\u003ePopulation characteristics are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The median age of the patients with delirium was significantly higher than that of the patients without delirium (82 vs 76 years, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). 54% (n\u0026thinsp;=\u0026thinsp;27) of patients with delirium were female compared to 41% (n\u0026thinsp;=\u0026thinsp;75) of patients without delirium. 94% of patients with delirium were 70 years of age or older. Median NEWS-score in the ED was 3 for patients with delirium compared to 1 for patients without delirium (p\u0026thinsp;=\u0026thinsp;0.004). 14% (n\u0026thinsp;=\u0026thinsp;7) of the patients with delirium had a known diagnosis of dementia, compared to 1.6% (n\u0026thinsp;=\u0026thinsp;3) for patients without delirium (p\u0026thinsp;=\u0026thinsp;0.001). This hospital admission was a readmission for 23% of all the patients. Readmissions were more prevalent in patients with delirium compared to patients with no delirium (42 vs 18%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001, see Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Overall, patients were mostly admitted to the department of internal medicine 33% (n\u0026thinsp;=\u0026thinsp;79), orthopaedic surgery 7% (n\u0026thinsp;=\u0026thinsp;17) and surgical departments 13% (n\u0026thinsp;=\u0026thinsp;31). Delirium patients showed a similar distribution regarding which departments they were admitted to.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003ePopulation characteristics and comparisons for acutely admitted patients\u0026thinsp;\u0026gt;\u0026thinsp;65 years and with and without delirium by DSM-V criteria during the hospitalization.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCharacteristic\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOverall\u003c/p\u003e\u003cp\u003eN\u0026thinsp;=\u0026thinsp;233\u003csup\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDelirium anytime during hospitalization\u003c/p\u003e\u003cp\u003eN\u0026thinsp;=\u0026thinsp;50\u003csup\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNo delirium during hospitalization\u003c/p\u003e\u003cp\u003eN\u0026thinsp;=\u0026thinsp;183\u003csup\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003ep-value\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e77 (72, 84)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e82 (76, 88)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e76 (70, 83)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSex\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e131(56%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e23(46%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e108(59%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFemale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e102(44%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e27(54%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e75(41%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNEWS score ED\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2.00 (0.00,3.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.00 (0.50, 5.50)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.00 (0.00, 3.00)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.004\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eUnknown\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e47 (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7(\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e40(\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKnown dementia*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e223(96%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e43(86%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e180(98%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10(4.3%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7(14%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3(1.6%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIs the admission a readmission?\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e179(77%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e29(58%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e150(82%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e54(23%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e21(42%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e33(18%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDelirium diagnosis at discharge?\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e229(98%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e46(92%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e183(100%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4(1.7%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4(8.0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0(0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDischarged home from ED?\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e174(75%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e48(96%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e126(69%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eYes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e59(25%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2(4.0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e57(31%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e\u003cp\u003e\u003csup\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sup\u003e\u0026nbsp;Median (IQR); n(%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e\u003cp\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026nbsp;Mann-Whitney u test; Pearson\u0026rsquo;s Chi-squared test; Fisher\u0026rsquo;s exact test\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e*Dementia was based on chart review from all the information in the patient\u0026rsquo;s hospital records related to the hospital admission in the study period to see if they had an documented diagnosis of dementia.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.4 Delirium screening and diagnosis at discharge\u003c/h2\u003e\u003cp\u003eOf all patients eligible for inclusion 96.7% (232 of 240) were screened by 4AT in the emergency department, and 70% (23 of 33) of the patients with delirium had a 4AT-score equal to or above 4, compared to 1% (2 of 207) of the patients with no delirium in the ED (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). A total of 8% (n\u0026thinsp;=\u0026thinsp;4) of patients with delirium by DSM-V criteria, both in the ED and during the consecutive hospitalisation, had a documented diagnosis of delirium at discharge from the hospital.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.5 Outcomes\u003c/h2\u003e\u003cp\u003eA comparison of outcomes for patients with and without delirium is visualized in Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Patients with delirium were more often discharged to a higher level of care, 48% vs 20% compared to patients without delirium, but when corrected for age, gender and severity of acute illness by NEWS2-score the difference was not statistically significant (p\u0026thinsp;=\u0026thinsp;0.156). 31% of acutely admitted patients\u0026thinsp;\u0026gt;\u0026thinsp;65 years without delirium were discharged directly home from the ED vs 4% (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) of patients with delirium. The length of hospital stay in whole days was significantly longer in patients with delirium (4.0 days, CI 2-9.5), compared to patients without delirium (2.0 days, CI 0\u0026ndash;4, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), adjusted for age, gender and severity of acute illness by NEWS-2 score.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eOutcomes comparing acutely admitted patients\u0026thinsp;\u0026gt;\u0026thinsp;65 years, with and without delirium during their hospitalization: higher level of care, length of hospital stay and cumulative 9-month mortality, corrected for age and severity of acute illness by The National Early Warning Score.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"8\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOverall, N\u0026thinsp;=\u0026thinsp;233\u003csup\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDelirium anytime during hospitalization, N\u0026thinsp;=\u0026thinsp;50\u003csup\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eNo delirium during hospitalization, N\u0026thinsp;=\u0026thinsp;183\u003csup\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eEstimates (95% CI)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003ep-value\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHigher level of care after hospitalization*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e21 (48)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e37 (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eOR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.83 (0.79; 4.22)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.156\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLength of hospital stay*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.0 (2.0-9.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.0 (0.0\u0026ndash;4.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eOR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1.72 (1.48; 2.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCumulative 9-month mortality *\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e26 (52)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e25 (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e\u003cp\u003eHR\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e2.90 (1.50; 5.62)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cem\u003e\u003csup\u003e1\u003c/sup\u003e\u003c/em\u003e\u0026nbsp; Median (IQR); n(%)\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003csup\u003e2\u003c/sup\u003e\u003c/em\u003e Logistic regression; Poisson regression; Cox regression\u003c/p\u003e\n\u003cp\u003e*NEWS score is missing for n=50 patients.\u003c/p\u003e\u003cp\u003eFor all patients included in this study, the 9-month mortality was 21%. Cumulative 9-month mortality was 52% (n\u0026thinsp;=\u0026thinsp;26) for patients with delirium, compared to 14% (n\u0026thinsp;=\u0026thinsp;25) for patients without delirium (p\u0026thinsp;=\u0026thinsp;0.002, HR 2.90 (1.50;5.62)), adjusted for age, gender and NEWS-2 score. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows Kaplan Meyer plots comparing days to death in patients with and without delirium during the hospitalization, corrected for age, gender and NEWS2-score, showing a significant difference in cumulative 9-month mortality between patients with and without delirium.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study found delirium to be common in acutely admitted older adults, with a point prevalence of 14% in the emergency department. The incidence was 8% during the rest of the hospitalisation for patients without delirium in the ED, giving a total occurrence of 21%. This is in line with estimates from a previous meta-analysis of published estimates of delirium occurrence in medical and geriatric inpatients over decades, showing an overall occurrence of 23% (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eOur study design allowed for an unselected inclusion of all acutely admitted patients which is important as many previous studies have examined specific cohorts of patients, such as medical geriatric patients (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e), oncological patients (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e), patients receiving non-invasive positive pressure ventilation (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e), acute medical patients (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e), or intensive care patients (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e). In later years the \u0026ldquo;delirium day\u0026rdquo; studies have aimed to estimate delirium point prevalence of acutely admitted patients, but with varying percentages of all acutely admitted patients included- such as 56% in a Norwegian study of medical and surgical wards (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e) and 84% in a study across 108 acute and 12 rehabilitation wards in Italy (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e). It is a potential challenge in delirium studies that systematic assessments of capacity for consent, may lead to the exclusion of patients with delirium (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e). We included a very high percentage (92.6%) of all the acutely admitted patients in the study period without obtaining consent but gave the patients an opportunity for reservation, as approved by the ethical committee. A large international study conducted by the World Delirium Awareness Day team reported on delirium prevalence at two specific time points during one day in 2023 (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e). In this study, 2502 wards or units started, yet only 66.5% (n\u0026thinsp;=\u0026thinsp;1664 wards) were analysed, meaning that even though the final number of patients was high the estimates of occurrence may have been biased. Ideally, delirium prevalence studies should include large numbers of patients and in addition include as many of the eligible patients as possible.\u003c/p\u003e\u003cp\u003eThe cut off for inclusion was \u0026gt;\u0026thinsp;65 years in our study, and the median age of the patients included was 77 years. The patients with delirium were with a median age of 82 years significantly older than the non-delirious patients. Knowing that delirium risk is increased with higher age, the estimates would be expected to increase if we set the inclusion age higher, e.g. at \u0026gt;\u0026thinsp;75 years. We chose 65 years as this is a commonly used definition of older adults, used among others by the United States National Institute of Aging (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e). Our finding that 94% of the patients with delirium were \u0026gt;\u0026thinsp;70 years is relevant in terms of which patient groups should be the focus of delirium identification. The National Institute for Health and Care Excellence guidelines highlight that patients aged\u0026thinsp;\u0026gt;\u0026thinsp;65 years are at an increased risk of delirium development (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). Yet, delirium identification in all admitted patients in this age group is resource demanding and a specification of which patients to prioritise for screening could be useful. Interestingly, for patients with delirium the current admission was a readmission for 42% compared to 18% for patients without a delirium. Potential reasons could be a higher burden of comorbidity or frailty in delirium patients. This finding is still relevant information for health care personnel working in the emergency departments, particularly if resources are scant and not sufficient to perform delirium identification in all patients\u0026thinsp;\u0026gt;\u0026thinsp;65 years. The high screening percentage of 96.7% in our study period is not indicative of the general screening rate of delirium in our emergency department. In our study only 70% of the patients who fulfilled a delirium diagnosis by DSM-V criteria had a 4AT score of 4 or above, which is low considering the diagnostic accuracy of the 4AT described previously (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). Our study has a unselected design meaning that 4AT could be less sensitive in this setting, which is supported by the findings of a sensitivity of 4AT of 76% in a randomized study performed in a similar setting (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e). We found that delirium patients are admitted to most of the departments examined in our study, highlighting the need for delirium knowledge and awareness throughout the hospital.\u003c/p\u003e\u003cp\u003e3% of the patients presented with subsyndromal delirium (SSD) during the hospitalization. We did not find a higher 9-month mortality in this group, which could be explained by a low number of patients. SSD is nonetheless relevant as several previous studies have shown that patients with SSD have an increased risk of negative outcomes (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eOnly 8% of patients with delirium had a formal diagnosis documented in their electronic chart at discharge, which is low, but expected given results from other studies (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e). This number stands in contrast to the identified delirium occurrence in our hospital and could indicate that most cases of delirium are never identified and thus not treated according to recommendations for good practice (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). Yet, it is uplifting to see that only 2 (4%) of patients with delirium were discharged directly home from the ED, indicating that the health care personnel have been aware of these patients and treated them in hospital. The increased risk of delirium development in dementia is well established (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e), and the patients with dementia had, as expected, a significantly higher occurrence of delirium in our study. The National Early Warning Score 2 (NEWS2) was significantly higher for delirium patients in our study, most likely indicating increased severity of the presenting illness in delirious patients. We found, in line with previous studies (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e), that length of hospital stay and mortality was significantly associated with delirium. Former studies have found 4AT\u0026thinsp;\u0026gt;\u0026thinsp;4 to be a strong predictor of death (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e). We did not find a statistically significant difference in level of care after discharge between patients with and without delirium when correcting for age and NEWS, which could be because delirium was not diagnosed and acknowledged. This finding was not in line with a previous meta-analysis which found delirium to be associated with an increased risk of institutionalisation [6]. A large 2025 study of more than 18000 hip fracture patients found delirium to be associated with a lower likelihood of returning home within 30 days (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eStrengths and limitations\u003c/p\u003e\u003cp\u003eA strength of our study is the high proportion of eligible patients included, as more than 92% of the target population for the study was included, which is rather high compared to similar studies. Our high inclusion rate is a strength in providing an accurate estimate of delirium prevalence and incidence. Stavanger University Hospital is the only hospital in our catchment area, meaning that hospitalised patients with delirium are not admitted elsewhere, which could be the case in other countries and cities where several hospitals share a specified catchment area. We have based our formal delirium diagnosis on The Diagnostic and Statistical Manual of Mental Disorders, Fifth Editions criteria (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e), conducted by two independent geriatricians experienced in delirium diagnosis. This is a strength, because although the sensitivity and specificity of the 4As test is high (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e), it does not represent a formal delirium diagnosis. For some patients an increased score on the 4As may not represent a delirium, particularly in patients with existing cognitive decline and dementia, where a formal diagnosis of delirium can be challenging (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e). It is well known that delirium estimates differ based on the diagnostic criteria used, with DMS-IV showing higher estimates than DSM-V (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e), which was used in our study. Our chart-based delirium diagnosis is a potential limitation compared to a more comprehensive diagnostic process in the clinic, yet patients were screened and assessed for delirium in the ED in addition to the chart-based method. It is also a strength that we estimate both a point prevalence and an incidence for delirium, as many studies in recent years provide only a delirium point prevalence (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e). No systematical daily delirium screening was conducted after the emergency department, which means that the retrospective diagnosis of delirium in the hospital wards is based on the notes in the medical record, which is a limitation. Systematically considering delirium daily throughout the hospitalisation could possibly have identified more patients with a hypoactive delirium and thus increased the estimates of delirium incidence.\u003c/p\u003e\u003cp\u003eThis study also has limitations: it was conducted in a single hospital, and only included patients for 5 days and 4 nights, which is a short period, and did not include the weekend. This could have led to a selection bias. We had to balance the need for a high inclusion rate to provide an accurate estimate of prevalence with the secondary aims of examining outcomes for delirium patients. It would be relevant to adjust our outcomes for frailty as well as for comorbidity to explore whether the negative outcomes observed in delirium patients might indeed be caused by delirium itself. To get a high inclusion rate, we were given approval from the ethic committee to collect information without obtaining consent from the participants first but were limited to collecting only some predefined data. Our primary aim was to investigate the occurrence of delirium, and we thus chose to prioritize this in the design of our study.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eWe found delirium to be common, with a total occurrence of 21% among hospitalised unselected older adults\u0026thinsp;\u0026gt;\u0026thinsp;65 years acutely admitted in the study period. Only 8% of those with delirium had a formal delirium diagnosis documented in the discharge summaries. Patients with delirium showed significantly increased length of stay and 9-month mortality. As the population ages and the number of people living with dementia increases, updated estimates of delirium prevalence in unselected cohorts are important to increase the attention and focus on delirium. Delirium prevention, identification and management are key aspects of a sustainable health care system facing an increasing proportion of older adults with multifaceted health issues and varying levels of cognitive dysfunction. Future studies should include a larger number of patients, diagnose delirium by verified diagnostic criteria and assess as high a percentage of all eligible patients as possible to provide accurate and non-biased estimates of delirium prevalence. Repeated cross-sectional studies could be relevant to examine the change of delirium prevalence over time.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e\u003cstrong\u003e4AT:\u0026nbsp;\u003c/strong\u003eThe 4 \u0026ldquo;A\u0026rdquo; s test\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDSM-V:\u003c/strong\u003e The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eED:\u003c/strong\u003e Emergency department\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eIQR:\u0026nbsp;\u003c/strong\u003eInter quartile range\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNEWS:\u0026nbsp;\u003c/strong\u003eNational Early Warning Score\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOSLA:\u003c/strong\u003e Observational Scale of Level of Arousal\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRASS:\u003c/strong\u003e Richmond Agitation Sedation Scale\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSESAM:\u003c/strong\u003e Centre for Age-Related Medicine\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSUH:\u003c/strong\u003e Stavanger University Hospital\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNIH:\u0026nbsp;\u003c/strong\u003eNational Institute of Aging\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNICE:\u0026nbsp;\u003c/strong\u003eNational Institute for Health and Care Excellence\u003c/p\u003e\n"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of interest:\u003c/strong\u003e the authors all declare no conflict of interest.\u003c/p\u003e\n\u003cp\u003eSupplementary figure showing a distribution of which departments patients with delirium were admitted to.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe conducted the study in accordance with the World Medical Association Declaration of Helsinki and the Regional Committee for Medical and Health Research Ethics of Western Norway approved the study prior to its start, in line with the Norwegian legislation- the research ethics act and the Health Research act. This committee is appointed by the Norwegian Ministry of Education and Health. The patients received written information with a possibility for reservation from participation in the study after discharge, as approved by the Regional Committee for Medical and Health Research Ethics (Western Norway; REK 424462). Patients who fulfilled inclusion criteria and died during or shortly after the study period were directly included as approved by the Regional Ethics Committee. The patients did not need to consent to participate in the study, this was approved by the Regional Committee for Medical and Health Research Ethics.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe dataset analyzed during the current study can upon request to the first author be made available, but only after application to and approval by The Regional Ethical Committee.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was funded by the Norwegian Health Association and The Western Norway Regional Health Authorities (Grant numbers F-12592 and F12614), and by Helse Stavanger by a grant from the Psychiatric Division.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eAuthors contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMNPH contributed to the concept, study design, collection of data, statistical analysis and drafted the manuscript. HS contributed to the concept, study design, collection of data and revised the manuscript. HBH contributed to the study design, statistical analysis and revised the manuscript. AOVM contributed to the study design and revised the manuscript. AD contributed to the study design and revised the manuscript. AS contributed to the study design, collection of data and revised the manuscript. RTWO contributed to the study design, collection of data and revised the manuscript. LOW contributed to the study design and revised the manuscript. DA contributed to the concept, study design and revised the manuscript. AKB contributed to the concept, study design and revised the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank the research nurses and staff of the emergency department at Stavanger University Hospital for their valuable contributions to this study.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAmerican Psychiatric Association.The Diagnostic and Statistical Manual of Mental Disorders: DSM-V. 5th edition. Washington, D.C:: American Psychiatric Association.; 2013.\u003c/li\u003e\n\u003cli\u003eWilson JE, Mart MF, Cunningham C, Shehabi Y, Girard TD, MacLullich AMJ, et al. Delirium. Nat Rev Dis Primers. 2020;6(1):90.\u003c/li\u003e\n\u003cli\u003eDeiner SG, Marcantonio ER, Trivedi S, Inouye SK, Travison TG, Schmitt EM, et al. Comparison of the frailty index and frailty phenotype and their associations with postoperative delirium incidence and severity. J Am Geriatr Soc. 2024;72(6):1781-92.\u003c/li\u003e\n\u003cli\u003eGibb K, Seeley A, Quinn T, Siddiqi N, Shenkin S, Rockwood K, Davis D. The consistent burden in published estimates of delirium occurrence in medical inpatients over four decades: a systematic review and meta-analysis study. Age Ageing. 2020;49(3):352-60.\u003c/li\u003e\n\u003cli\u003eTitlestad I, Haugarvoll K, Solvang SH, Norekv\u0026aring;l TM, Skogseth RE, Andreassen OA, et al. Delirium is frequently underdiagnosed among older hospitalised patients despite available information in hospital medical records. Age Ageing. 2024;53(2).\u003c/li\u003e\n\u003cli\u003eWitlox J, Eurelings LS, de Jonghe JF, Kalisvaart KJ, Eikelenboom P, van Gool WA. Delirium in elderly patients and the risk of postdischarge mortality, institutionalization, and dementia: a meta-analysis. Jama. 2010;304(4):443-51.\u003c/li\u003e\n\u003cli\u003eHan JH, Eden S, Shintani A, Morandi A, Schnelle J, Dittus RS, et al. Delirium in older emergency department patients is an independent predictor of hospital length of stay. Acad Emerg Med. 2011;18(5):451-7.\u003c/li\u003e\n\u003cli\u003eGoldberg TE, Chen C, Wang Y, Jung E, Swanson A, Ing C, et al. Association of Delirium With Long-term Cognitive Decline: A Meta-analysis. JAMA Neurol. 2020;77(11):1373-81.\u003c/li\u003e\n\u003cli\u003eKrogseth M, Davis D, Jackson TA, Zetterberg H, Watne LO, Lindberg M, et al. Delirium, neurofilament light chain, and progressive cognitive impairment: analysis of a prospective Norwegian population-based cohort. Lancet Healthy Longev. 2023;4(8):e399-e408.\u003c/li\u003e\n\u003cli\u003eCaplan GA, Teodorczuk A, Streatfeild J, Agar MR. The financial and social costs of delirium. European geriatric medicine. 2020;11(1):105-12.\u003c/li\u003e\n\u003cli\u003eInouye SK, Bogardus ST, Jr., Charpentier PA, Leo-Summers L, Acampora D, Holford TR, Cooney LM, Jr. A multicomponent intervention to prevent delirium in hospitalized older patients. The New England Journal of Medicine. 1999;340(9):669-76.\u003c/li\u003e\n\u003cli\u003eLudolph P, Stoffers-Winterling J, Kunzler AM, Rosch R, Geschke K, Vahl CF, Lieb K. Non-Pharmacologic Multicomponent Interventions Preventing Delirium in Hospitalized People. Journal of American Geriatrics Society. 2020;68(8):1864-71.\u003c/li\u003e\n\u003cli\u003eAkunne A, Murthy L, Young J. Cost-effectiveness of multi-component interventions to prevent delirium in older people admitted to medical wards. Age Ageing. 2012;41(3):285-91.\u003c/li\u003e\n\u003cli\u003e(SIGN) SIGN. Risk reduction and management of delirium. Edinburgh: SIGN; 2019. 2019 [07.10.2024]. Available from: https://www.sign.ac.uk/media/1423/sign157.pdf.\u003c/li\u003e\n\u003cli\u003eNational Institute for Health and Care Excellence (NICE). Delirium: prevention, diagnosis and management in hospital and long-term care: National Institute for Health and Care Excellence; 2010 [updated 18.01.2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553009/.\u003c/li\u003e\n\u003cli\u003eFiliatreault S, Grimshaw JM, Kreindler SA, Chochinov A, Linton J, Chatterjee R, et al. A critical appraisal and recommendation synthesis of delirium clinical practice guidelines relevant to the care of older adults in the emergency department: An umbrella review. J Eval Clin Pract. 2023;29(6):1039-53.\u003c/li\u003e\n\u003cli\u003eNummedal MA, Markussen DL, N\u0026aelig;ss LE, Laugsand LE, Bj\u0026oslash;rnsen LP. Patient influx to emergency departments at two Norwegian university hospitals from 2012-21. Tidsskr Nor Laegeforen. 2024;144(8).\u003c/li\u003e\n\u003cli\u003eGj\u0026oslash;ra L, Strand BH, Bergh S, Borza T, Br\u0026aelig;khus A, Engedal K, et al. Current and Future Prevalence Estimates of Mild Cognitive Impairment, Dementia, and Its Subtypes in a Population-Based Sample of People 70 Years and Older in Norway: The HUNT Study. J Alzheimers Dis. 2021;79(3):1213-26.\u003c/li\u003e\n\u003cli\u003eEstimation of the global prevalence of dementia in 2019 and forecasted prevalence in 2050: an analysis for the Global Burden of Disease Study 2019. Lancet Public Health. 2022;7(2):e105-e25.\u003c/li\u003e\n\u003cli\u003eHealths NDo. Reinnleggelse blant eldre 30 dager etter utskrivning [12.03.2025]. Available from: https://www.helsedirektoratet.no/statistikk/kvalitetsindikatorer/behandling-av-sykdom-og-overlevelse/reinnleggelse-blant-eldre-30-dager-etter-utskrivning#:~:text=Reinnleggelse%20er%20definert%20som%20en,en%20utskrivning%20fra%20et%20sykehus.\u003c/li\u003e\n\u003cli\u003ePhysicians RCO. National Early Warning Score (NEWS) 2 Standardising the assessment of acute-illness severity in the NHS. 2017 [05.05.2025]. Available from: https://www.rcp.ac.uk/media/a4ibkkbf/news2-final-report_0_0.pdf.\u003c/li\u003e\n\u003cli\u003eTieges Z, Maclullich AMJ, Anand A, Brookes C, Cassarino M, O\u0026apos;Connor M, et al. Diagnostic accuracy of the 4AT for delirium detection in older adults: systematic review and meta-analysis. Age Ageing. 2021;50(3):733-43.\u003c/li\u003e\n\u003cli\u003eSessler CN, Gosnell MS, Grap MJ, Brophy GM, O\u0026apos;Neal PV, Keane KA, et al. The Richmond Agitation-Sedation Scale: validity and reliability in adult intensive care unit patients. Am J Respir Crit Care Med. 2002;166(10):1338-44.\u003c/li\u003e\n\u003cli\u003eTieges Z, McGrath A, Hall RJ, Maclullich AM. Abnormal level of arousal as a predictor of delirium and inattention: an exploratory study. Am J Geriatr Psychiatry. 2013;21(12):1244-53.\u003c/li\u003e\n\u003cli\u003eWatne LO, Pollmann CT, Neerland BE, Quist-Paulsen E, Halaas NB, Idland AV, et al. Cerebrospinal fluid quinolinic acid is strongly associated with delirium and mortality in hip-fracture patients. Journal of Clinical Investigation. 2023;133(2).\u003c/li\u003e\n\u003cli\u003eEvensen S, Saltvedt I, Lydersen S, Wyller TB, Taraldsen K, Sletvold O. Environmental factors and risk of delirium in geriatric patients: an observational study. BMC Geriatr. 2018;18(1):282.\u003c/li\u003e\n\u003cli\u003eGrandahl MG, Nielsen SE, Koerner EA, Schultz HH, Arnfred SM. Prevalence of delirium among patients at a cancer ward: Clinical risk factors and prediction by bedside cognitive tests. Nord J Psychiatry. 2016;70(6):413-7.\u003c/li\u003e\n\u003cli\u003eChan KY, Cheng LS, Mak IW, Ng SW, Yiu MG, Chu CM. Delirium is a Strong Predictor of Mortality in Patients Receiving Non-invasive Positive Pressure Ventilation. Lung. 2017;195(1):115-25.\u003c/li\u003e\n\u003cli\u003ePendlebury ST, Lovett NG, Smith SC, Dutta N, Bendon C, Lloyd-Lavery A, et al. Observational, longitudinal study of delirium in consecutive unselected acute medical admissions: age-specific rates and associated factors, mortality and re-admission. BMJ Open. 2015;5(11):e007808.\u003c/li\u003e\n\u003cli\u003eKrewulak KD, Stelfox HT, Leigh JP, Ely EW, Fiest KM. Incidence and Prevalence of Delirium Subtypes in an Adult ICU: A Systematic Review and Meta-Analysis. Crit Care Med. 2018;46(12):2029-35.\u003c/li\u003e\n\u003cli\u003eInstenes I, Eide LSP, Andersen H, F\u0026aring;lun N, Pettersen T, Ranhoff AH, et al. Detection of delirium in older patients-A point prevalence study in surgical and non-surgical hospital wards. Scand J Caring Sci. 2024;38(3):579-88.\u003c/li\u003e\n\u003cli\u003eBellelli G, Morandi A, Di Santo SG, Mazzone A, Cherubini A, Mossello E, et al. \u0026quot;Delirium Day\u0026quot;: a nationwide point prevalence study of delirium in older hospitalized patients using an easy standardized diagnostic tool. BMC Medicine. 2016;14:106.\u003c/li\u003e\n\u003cli\u003eAdamis D, Martin FC, Treloar A, Macdonald AJ. Capacity, consent, and selection bias in a study of delirium. J Med Ethics. 2005;31(3):137-43.\u003c/li\u003e\n\u003cli\u003eLindroth H, Liu K, Szalacha L, Ashkenazy S, Bellelli G, van den Boogaard M, et al. World delirium awareness and quality survey in 2023-a worldwide point prevalence study. Age Ageing. 2024;53(11).\u003c/li\u003e\n\u003cli\u003eAging NIo. Age 2025 [Available from: https://www.nih.gov/nih-style-guide/age#:~:text=The%20National%20Institute%20on%20Aging,these%20terms%2C%20ask%20for%20specifics.\u003c/li\u003e\n\u003cli\u003eShenkin SD, Fox C, Godfrey M, Siddiqi N, Goodacre S, Young J, et al. Delirium detection in older acute medical inpatients: a multicentre prospective comparative diagnostic test accuracy study of the 4AT and the confusion assessment method. BMC Med. 2019;17(1):138.\u003c/li\u003e\n\u003cli\u003eShim J, DePalma G, Sands LP, Leung JM. Prognostic Significance of Postoperative Subsyndromal Delirium. Psychosomatics. 2015;56(6):644-51.\u003c/li\u003e\n\u003cli\u003eCole M, McCusker J, Dendukuri N, Han L. The prognostic significance of subsyndromal delirium in elderly medical inpatients. J Am Geriatr Soc. 2003;51(6):754-60.\u003c/li\u003e\n\u003cli\u003eIbitoye T, So S, Shenkin SD, Anand A, Reed MJ, Vardy E, et al. Delirium is under-reported in discharge summaries and in hospital administrative systems: a systematic review. Delirium (Bielef). 2023;2023:74541.\u003c/li\u003e\n\u003cli\u003eFong TG, Inouye SK. The inter-relationship between delirium and dementia: the importance of delirium prevention. Nature Reviews Neurology. 2022;18(10):579-96.\u003c/li\u003e\n\u003cli\u003eAnand A, Cheng M, Ibitoye T, Maclullich AMJ, Vardy E. Positive scores on the 4AT delirium assessment tool at hospital admission are linked to mortality, length of stay and home time: two-centre study of 82,770 emergency admissions. Age Ageing. 2022;51(3).\u003c/li\u003e\n\u003cli\u003ePenfold RS, Farrow L, Hall AJ, Clement ND, Ward K, Donaldson L, et al. Delirium on presentation with a hip fracture is associated with adverse outcomes : a multicentre observational study of 18,040 patients using national clinical registry data. Bone Joint J. 2025;107-b(4):470-8.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Appendix 1","content":"\u003cp\u003eAppendix 1 is not available with this version.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-geriatrics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bgtc","sideBox":"Learn more about [BMC Geriatrics](http://bmcgeriatr.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bgtc/default.aspx","title":"BMC Geriatrics","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"delirium, prevalence, occurrence, older adults, incidence, acute-hospital, emergency-department, outcomes, mortality, length-of-stay, screening, 4AT, under-reported","lastPublishedDoi":"10.21203/rs.3.rs-7184588/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7184588/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eDelirium is common in acutely ill older adults and is associated with multiple unfavourable outcomes, including an increased risk of dementia and death. As the population ages and more people live with dementia, updated and accurate estimates of delirium prevalence are important. The primary aim of this study was to identify delirium point prevalence in the emergency department and incidence during hospitalisation. Our secondary aim was to compare outcomes: length of stay, need for a higher level of care, and mortality after discharge in patients with and without delirium.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eIn this unselected observational cohort study, all older adults aged 65 years or above acutely admitted to the emergency department of a large Norwegian hospital during a 5-day and 4-night midweek period, were screened for delirium by the 4 \u0026ldquo;A\u0026rdquo;s test. A final consensus delirium diagnosis was made based on review of all available information in the patients\u0026rsquo; electronic health record to consider if The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition\u0026rsquo;s criteria (DSM-V) for delirium were fulfilled.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eOf 240 patients assessed, 14% (n\u0026thinsp;=\u0026thinsp;33) fulfilled DSM-V criteria for delirium in the emergency department, and 8% (n\u0026thinsp;=\u0026thinsp;17) of the remaining 207 patients developed delirium later during the hospitalization. Only 4 of the 50 patients with delirium (8%) had a documented diagnosis of delirium in their discharge summary. For patients with delirium, the current hospital admission was more often a readmission (42% vs 18%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Delirium patients also had longer hospitalizations (4 vs 2 days, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), and higher 9-month mortality (52% vs 13%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), corrected for age, gender and severity of acute illness by The National Early Warning Score 2.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e\u003cp\u003eDelirium was common and underdiagnosed in our study and associated with unfavourable outcomes for the patients. Delirium prevention, identification and management should be key priorities for the health care system.\u003c/p\u003e\u003ch2\u003eTrial registration\u003c/h2\u003e\u003cp\u003eOur article does not report results of a health care intervention, and the protocol is not registered in a trial registry.\u003c/p\u003e","manuscriptTitle":"Delirium prevalence and incidence in acutely admitted older patients: an observational cohort study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-12 13:03:08","doi":"10.21203/rs.3.rs-7184588/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-30T13:31:37+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-15T20:12:25+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"171917729163266025296793003538611443015","date":"2025-10-15T17:33:52+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"188014491460874548651991795237875510754","date":"2025-09-09T14:24:05+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-02T10:30:48+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"281042739607440519159901515587920427679","date":"2025-08-28T09:23:25+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"69349179560858495944080728183029896462","date":"2025-08-06T22:47:53+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-06T18:42:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-29T13:13:15+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-07-29T08:41:52+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-29T07:52:49+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Geriatrics","date":"2025-07-29T07:48:43+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-geriatrics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bgtc","sideBox":"Learn more about [BMC Geriatrics](http://bmcgeriatr.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bgtc/default.aspx","title":"BMC Geriatrics","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"18667a55-9abb-45c9-8bab-2daf05fefed5","owner":[],"postedDate":"August 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-22T16:06:14+00:00","versionOfRecord":{"articleIdentity":"rs-7184588","link":"https://doi.org/10.1186/s12877-025-06903-8","journal":{"identity":"bmc-geriatrics","isVorOnly":false,"title":"BMC Geriatrics"},"publishedOn":"2025-12-19 15:58:13","publishedOnDateReadable":"December 19th, 2025"},"versionCreatedAt":"2025-08-12 13:03:08","video":"","vorDoi":"10.1186/s12877-025-06903-8","vorDoiUrl":"https://doi.org/10.1186/s12877-025-06903-8","workflowStages":[]},"version":"v1","identity":"rs-7184588","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7184588","identity":"rs-7184588","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}