Comparison of serum 25-hydroxyvitamin D levels between patients with multiple chemical sensitivity and healthy controls: A case–control study

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Whether such an association exists in multiple chemical sensitivity (MCS) has not been clarified. This study aimed to compare serum 25-hydroxyvitamin D (25[OH]D) concentrations between patients with MCS and healthy controls. We conducted a case–control study including 80 female patients with physician-diagnosed MCS and 5,518 controls. Serum 25(OH)D concentrations were compared using a general linear model with bias-corrected and accelerated bootstrap resampling (1,000 iterations), adjusting for age, sex, season of blood collection, smoking status, body mass index, alcohol intake, and physical activity. Vitamin D deficiency (< 20 ng/mL) was highly prevalent in both groups (78.8% in MCS vs. 75.3% in controls). Median serum 25(OH)D concentrations did not differ significantly between groups (14.6 vs. 15.6 ng/mL, p = 0.622). Adjusted analyses confirmed no statistically significant difference (adjusted difference = 1.07 ng/mL, 95% CI: −0.18 to 2.46, p = 0.119). Despite the high prevalence of vitamin D deficiency, patients with MCS did not differ significantly from controls in serum 25(OH)D concentrations. These findings indicate that vitamin D status does not distinguish individuals with MCS from the general population. Further longitudinal and mechanistic studies are warranted to clarify the potential relationship between vitamin D and MCS. Health sciences/Biomarkers Health sciences/Diseases Health sciences/Medical research Health sciences/Neurology Biological sciences/Neuroscience multiple chemical sensitivity vitamin D 25-hydroxyvitamin D Figures Figure 1 1. Introduction Vitamin D deficiency is associated with bone-related diseases as well as neurological dysregulation such as multiple sclerosis, mood disorders, and schizophrenia [ 1 – 6 ]. Furthermore, vitamin D deficiency is associated with allergic diseases such as asthma, atopic dermatitis, and allergic rhinitis [ 7 – 10 ]. This evidence suggests the possibility that vitamin D plays a role in neurological and allergic diseases. Multiple chemical sensitivity (MCS) shares the same aspects as neurological and allergic diseases. In terms of hypersensitivity, MCS is a disorder characterized by reactions to trace amounts of chemicals or environmental agents that healthy people do not react to, causing multisystem symptoms such as headache, dizziness, cough, and abdominal pain [ 11 , 12 ]. Additionally, MCS frequently co-occurs with allergic diseases such as allergic rhinitis [ 13 , 14 ]. From a neurological standpoint, MCS is a type of central sensitization syndrome in which brain or nerve hypersensitivity is thought to be involved [ 15 , 16 ]. Considering the immunological and neurological aspects of vitamin D and MCS, it is important to clarify whether vitamin D is involved in the development of MCS. Although the association between vitamin D and MCS has been discussed from a neurological perspective [ 17 ], a direct comparison of serum 25-hydroxyvitamin D (25[OH]D) levels between healthy individuals and individuals with MCS has not been reported. To this end, we aimed to compare the serum 25(OH)D status of MCS patients compared with that of healthy controls. 2. Material and methods 2.1. Study design In this case-control study, we included consecutive female patients diagnosed with MCS at the Immunology and Allergy Center of Shona Kamakura General Hospital between April 2023 and April 2024 as the MSC group. For the control group, we included all consecutive individuals who underwent routine medical examinations at the Centre for Preventive Medicine, Jikei University School of Medicine, and the Toriton Clinic of Jikei University Hospital in Tokyo between April 2019 and March 2020, excluding December 2019 and whose 25(OH)D levels were determined in a previous study [ 18 ]. The case group (n = 80) and the control group (n = 5,518) were recruited from geographically adjacent areas (Tokyo and Kanagawa) located at similar latitudes to minimize differences in environmental UV exposure. 2.2. Method for measuring serum 25 (OH) D Serum 25(OH)D levels in the case groups were measured using an electrochemiluminescence immunoassay (ECLIA). For the control group, 25(OH)D levels were determined using a fully automated LC-MS/MS platform consisting of the CLAM-2030 sample preparation module and the LCMS-8050 triple quadrupole mass spectrometer (both from Shimadzu Corporation). The correlation between ECLIA and LC-MS/MS methods has been verified in a previous study [ 18 ] (r = 0.949), and the equation used to determine this correlation is as follows: ( y [ECLIA] = 1.000×[LC-MS/MS] + 0.850). As such, serum 25(OH)D levels of the two groups were compared based on their ECLIA values. 2.3. Classification of 25(OH)D levels Levels of 25(OH)D were classified as follows: sufficient (≥ 30 ng/mL), insufficient (20–29.9 ng/mL), and deficient (< 20 ng/mL) [ 19 , 20 ]. 2.4. Diagnosis of multiple chemical sensitivity The Quick Environmental Exposure and Sensitivity Inventory (QEESI) is a commonly utilized questionnaire with demonstrated high diagnostic accuracy for identifying multiple chemical sensitivity (MCS), exhibiting a sensitivity of 92% and specificity of 95% [ 21 – 24 ]. This tool has been applied in MCS research across several countries, including the United States, Japan, and Germany. A validated Japanese version of the QEESI is also available [ 22 ]. The instrument comprises five distinct domains: (1) chemical exposures, (2) other exposures, (3) symptoms, (4) masking index, and (5) impact of sensitivity. All sections, except the masking index, are scored on a 0–100 scale. Additionally, risk stratification criteria are applied to the chemical exposure (1), symptoms (3), and masking index (4) sections. Individuals scoring 40 points or more in both the chemical exposure and symptoms domains are categorized as “highly suggestive” of MCS, a criterion employed for participant selection in this study. Further methodological details are outlined below. The QEESI is a self-reported assessment tool that captures individuals’ reactions to various environmental exposures, such as chemicals, food items, skin contactants, alcohol, and caffeine. Each of the first three scales — Chemical Exposures, Other Exposures, and Symptoms — comprises 10 items. Respondents rate their responses on a scale from 0 (no reaction) to 10 (severe reaction), based on symptom severity. The development and psychometric validation of these scales, including their sensitivity and specificity, have been described in earlier studies. 2.5. Chemical exposures scale (1) This domain evaluates participants’ sensitivity to ten diverse airborne substances. Participants assign a severity score from 0 to 10 for each item, which includes exposures such as exhaust from diesel or gasoline engines, tobacco smoke, pesticides, gasoline fumes, paints and thinners, scented products, cleaning agents, fresh asphalt or tar, nail products, hair spray, and new furniture. 2.6. Symptoms scale (3) This domain assesses a broad range of symptom categories, including head-related, musculoskeletal, respiratory and mucosal, cardiovascular, neuromuscular, gastrointestinal, cognitive, emotional, dermatologic, and genitourinary symptoms. Participants rate each symptom based on severity, where 0 indicates no symptoms, 5 indicates moderate symptoms, and 10 indicates severe or disabling symptoms. The total score for this scale ranges from 0 to 100, calculated by summing the scores of all 10 items. To enhance the accuracy of case identification, both the QEESI criteria and physician-confirmed diagnoses were employed in determining MCS status among participants. 2.7. Statistical analysis Because serum 25(OH)D levels are influenced by demographic and lifestyle factors such as age, sex, season of blood collection, smoking status, body mass index, alcohol intake, and physical activity [ 18 , 25 – 27 ], these variables were included as covariates in the general linear model with bias-corrected and accelerated bootstrap resampling. The distribution of serum 25(OH)D levels exhibited a slight leftward shift of the peak, resembling a log-normal distribution with noticeable deviation in skewness from a normal distribution. Therefore, bias-corrected and accelerated (BCa) bootstrap resampling was employed, given its robustness in handling skewed data with SPSS software (version 30; IBM Corp, Armonk, NY, USA). A p-value < 0.05 was considered statistically significant. 2.8. Ethics approval The central ethics committee of Tokusyukai approved the study protocol (No. TGE02540-024). All methods were performed in accordance with the relevant guidelines and regulations, including the Declaration of Helsinki and the Ethical Guidelines for Medical and Health Research Involving Human Subjects in Japan. For the case group, an opt-out approach was employed in accordance with these ethical guidelines, while written informed consent for secondary use of data was obtained from all participants in the control group. 3. Results Of 89 individuals included in the MCS cohort during the specified period, 9 individuals were excluded because of supplemental administration of vitamin D during the initial visit. The control group included data from 5,518 individuals; however, their vitamin D supplement administration was unknown. In European countries and the United States, people actively consume vitamin D through supplements, and 25(OH)D₂ is often added to foods; therefore, the 25(OH)D₂ concentrations detected in populations in these regions are higher than those observed in the Japanese study [ 18 ]. In the data of controls, the 25(OH)D₂ levels in most participants were below the detection limit, suggesting that vitamin D supplements are not commonly used in this control group [ 18 ]. Therefore, in total, 80 cases and 5,518 controls were included in the analysis. We found that 78.8% of the individuals in the MCS group had vitamin D deficiency, and no significant difference was observed when compared with the rate in the control group (75.3%; Table 1 ). The serum 25(OH)D levels of the MCS group (measured by ECLIA) were not significantly different from that of the control group after conversion of LC-MS/MS values to ECLIA values [ 16 ] (median [interquartile range]: 14.6 [11.8–19.4] vs. 15.6 [12.0–20.0] ng/mL, p = 0.622]; Table. 1). The adjusted analysis using a general linear model with bootstrap resampling (1,000 samples) showed no statistically significant difference in serum 25(OH)D₃ levels between the case and control groups after adjusting for sex, measurement season, smoking status, age, BMI, alcohol index, and physical activity (Difference = 1.07, 95% CI [BCa]: −0.18 to 2.46, p = 0.119; Table 2 ). Among the covariates, sex, age, time of blood sampling, and alcohol index were significant predictors of serum 25(OH)D levels, while BMI and physical activity were not. Smoking showed a borderline effect (p = 0.069; Table 2 ). Adjusted means were 17.04 ng/mL (95% CI [BCa]: 15.81–18.38) for the case group and 15.98 ng/mL (95% CI [BCa]: 15.48–16.45) for the control group, with an adjusted difference of 1.07 ng/mL (95% CI [BCa]: −0.18 to 2.46, p = 0.119; Table 3 , Fig. 1 ). Table 1 Demographics and serum 25(OH)D levels Case group, n = 80 Control group, n = 5,518 P value Sex, female/male 77/3 2,118/3,400 < 0.001 Age (years), median (IQR) 53 (43–65) 50 (39–59) 0.005 Time of blood sampling Winter (January to March), n (%) 16 (20.0) 600 (10.9) < 0.001 Spring (April to June), n (%) 16 (20.0) 2,800 (50.7) Summer (July to September), n (%) 14 (17.5) 2,088 (37.8) Fall (October to December), n (%) 34 (42.5) 30 (0.5) Smoking [Current/ (past + never)] 597/4921 0/80 0.002 BMI (kg/m²) 22.6 (19.8–25.1) 22.4 (20.3–24.7) 0.874 Alcohol index (g/day) 0 (0–0) 0 (0–137) < 0.001 Physical activity (min/day) 0 (0–0) 30 (0–60) < 0.001 Levels of 25-hydroxyvitamin D 25(OH)D, median (IQR), (ng/mL) 14.6 (11.8–19.4) 15.6 (12.0–20.0) † 0.622 Sufficient as ≥ 30 ng/mL, n (%) 2 (2.5) 145 (2.6) 0.765 Insufficiency as 20–29.9 ng/mL, n (%) 15 (18.8) 1,220 (22.1) Deficiency as < 20 ng/mL, n (%) 63 (78.8) 4,153 (75.3) IQR, interquartile range; 25-hydroxyvitamin D, 25(OH)D † The values of the control group are adjusted values calculated using the following formula. The correlation between ECLIA and LC-MS/MS methods has been verified in the previous studiy 6 , r = 0.949 (P < 0.01), and the equation describing this correlation is y (ECLIA) = 1.000 x (LC-MS/MS) + 0.850. Table 2 General Linear Model with Bootstrap Variables B (Estimate) 95% CI (BCa) Bootstrap p-value Group (Ref. control) Case 1.07 −0.18 to 2.46 0.119 Sex (Ref. female) Male 2.11 1.77 to 2.43 0.001 Age (year) 0.077 0.064 to 0.088 0.001 Time of blood sampling [Ref. Winter (Jan to Mar)] Spring (Apr to Jun) 1.43 0.93 to 1.97 0.001 Summer (Jul to Sep) 1.15 0.62 to 1.69 0.001 Fall (Oct to Dec) 0.63 −1.11 to 2.21 0.448 Smoking (Ref. Current) Others (past + never) −0.54 −1.14 to 0.04 0.069 BMI (kg/m²) −0.033 −0.080 to 0.012 0.160 Alcohol index 0.001 0.000 to 0.002 0.014 Physical activity (min/day) −0.001 −0.003 to 0.002 0.679 Dependent variable: Serum 25(OH)D, ng/mL BCa, bias-corrected and accelerated bootstrap confidence interval (1,000 resamples) Table 3 Adjusted Means of Serum 25(OH)D by Group Group Adjusted Mean (ng/mL) 95% CI (BCa) Case 17.04 15.81 to 18.38 Control 15.98 15.48 to 16.45 Difference (Case – Control) 1.07 −0.18 to 2.46 Bootstrap p-value for adjusted difference: 0.119 (not significant). BCa, bias-corrected and accelerated bootstrap confidence interval (1,000 resamples) 4. Discussion 4.1. Comparison of 25(OH)D levels between MCS patients and healthy controls To our knowledge, this is the first study to compare 25(OH)D levels between patients with MCS and healthy controls. We found that although a high percentage of patients with MCS (78.8%) had vitamin D deficiency, an adjusted analysis using a general linear model with bootstrap resampling revealed no significant difference in 25(OH)D levels between patients with MCS and healthy controls. Our findings indicate that sex, age, and seasonal variation were observed to be associated with vitamin D status, whereas BMI and physical activity were not significant predictors. Interestingly, alcohol intake showed a modest positive association with serum 25(OH)D₃, while current smoking exhibited a borderline negative association. These results are consistent with previous reports highlighting the influence of seasonal sunlight exposure and age-related metabolic changes on vitamin D levels [ 26 , 28 ]. The lack of a significant group effect suggests that the observed differences in vitamin D status may primarily reflect demographic and behavioral factors rather than disease status itself. 4.2. Contradictory findings in previous studies In a previous study, vitamin D levels in patients with multiple sclerosis show no significant difference compared to that of healthy controls, with both groups exhibiting low levels [ 29 ]. However, another study revealed significant differences, yielding contradictory results [ 30 ]. These discrepancies may be because 25(OH)D levels can vary depending on measurement conditions, such as age, sex, and seasonal variations in UV exposure[ 18 ]. Therefore, in this study, analyses were adjusted for sex, age, season of blood collection, smoking status, body mass index, alcohol consumption, and physical activity. Moreover, the hospitals attended by the patient and control groups were in nearby areas, and the climate and the number of hours of sunlight were approximately the same. 4.3. Potential role of vitamin D in inflammatory diseases Research has suggested an inverse relationship between 25(OD)D levels and disease activity under various inflammatory conditions. Patients with rheumatoid arthritis have lower vitamin D levels than healthy controls, with a negative correlation between serum 25(OH)D levels and disease severity [ 31 ]. Similarly, in early inflammatory polyarthritis, higher 25(OH)D levels are associated with lower disease activity and C-reactive protein levels [ 32 ]. For ankylosing spondylitis, cross-sectional studies have indicated lower vitamin D levels in patients than in controls, with some evidence of an inverse correlation between 25(OH)D and disease activity [ 33 ]. Active patients with Behçet’s disease have significantly lower serum 25(OH)D levels than healthy controls and inactive patients [ 34 ]. These findings suggest a potential immunomodulatory role of vitamin D in inflammatory diseases, although longitudinal studies are needed to establish causality. While the relationship between MCS severity and serum 25(OH)D level is also interesting, we did not assess this relationship in this study. Notably, the assessment of MCS severity is subjective, as there are currently no established objective markers. 4.4. Uncertainty in the effectiveness of Vitamin D supplementation To date, the results of randomized controlled trials have been inconsistent, and clear evidence of the effects of vitamin D is difficult to achieve [ 35 , 36 ]. With respect to the efficacy of vitamin D supplementation, the minimum effective serum 25(OH)D level is thought to vary with disease. This may be because the cut-off levels of serum 25(OH)D indicating deficiency or sufficiency may be disease-dependent, just as vitamin D metabolism is tissue-dependent [ 37 ]. Therefore, the relationship between vitamin D levels and disease activity remains unclear and may vary by disease. These insights provide important guidance for considering an appropriate approach for vitamin D supplementation therapy. 4.5. Study limitations This study has several limitations. First, although we adjusted for age, sex, season of blood collection, smoking status, BMI, alcohol consumption, and physical activity, other potential determinants of serum 25(OH)D levels such as dietary intake, comorbid conditions, or genetic polymorphisms were not assessed. Second, sun exposure, which is a major determinant of vitamin D status, was not directly measured in this study. Although previous studies have shown that sun exposure generally influences serum 25(OH)D levels [ 38 , 39 ], a study reported no significant association between sun exposure and serum vitamin D in multiple sclerosis patients, while an effect remained in healthy controls [ 29 ]. Therefore, the potential influence of sun exposure on our results cannot be completely excluded. Third, the sample size of the MCS group was relatively small compared to the large control cohort, which may have limited the statistical power to detect subtle differences. Finally, the case–control design restricts causal inference, and the cross-sectional assessment precludes evaluation of temporal or disease-severity–related associations between vitamin D status and MCS. 5. Conclusion In this case–control study, no significant differences in serum 25(OH)D levels were observed between patients with MCS and healthy controls after adjusting for demographic and lifestyle factors. While vitamin D deficiency was prevalent in both groups, our findings suggest that reduced vitamin D levels are unlikely to represent a disease-specific marker of MCS. These results should be interpreted with caution given the observational design and limited case sample size. Future longitudinal and mechanistic studies are warranted to clarify whether vitamin D plays any contributory or modulatory role in the pathophysiology of MCS. Abbreviations 25(OH)D: 25-hydroxyvitamin D ECLIA: electrochemiluminescence immunoassay LC-MS/MS: liquid chromatography-tandem mass spectrometry MCS: multiple chemical sensitivity Declarations Ethics approval and consent to participate The central ethics committee of Tokusyukai approved the study protocol (No. TGE02540-024). For the case group, an opt-out approach was employed in accordance with ethical guidelines, while written informed consent for secondary use of data was obtained from all participants in the control group. Consent for publication Not applicable. Availability of data and materials Due to ethical considerations, the dataset is not publicly available. However, pseudonymized data may be provided by the corresponding author upon a justified request. Competing interests All authors declare that they have no conflicts of interest related to this work. Funding statement The authors declare that this work was carried out independently and did not benefit from any designated funding from public, commercial, or philanthropic sources. Authors’ contributions KW, SO, and TM conceptualized and designed the study. Data collection was carried out by KW, SO, and TM. Statistical analyses were performed by KW and KA. Data interpretation involved contributions from KW, SO, and TM. The manuscript was drafted by KW, with KA providing critical revisions. All authors reviewed and approved the final manuscript. Acknowledgements We sincerely thank all patients with MCS and healthy control participants for their valuable contribution to this study. References Nakamura, K. et al . The Murakami Cohort Study of vitamin D for the prevention of musculoskeletal and other age-related diseases: a study protocol. Environ. Health Prev. Med. 23 , 28 (2018). Yu, X. H. et al. Association between 25(OH) vitamin D and multiple sclerosis: cohort, shared genetics, and Causality. Nutr. J. 23 , 151 (2024). Alelyani, M. et al . Assessment of vitamin D status and associated risk factors in high-altitude populations affected by multiple sclerosis: A case-control study. Medicine 103 , e38369 (2024). Hollinshead, V. R. B. B., Piaskowski, J. L. & Chen, Y. Low vitamin D concentration is associated with increased depression risk in adults 20-44 years old, an NHANES 2007-2018 data analysis with a focus on perinatal and breastfeeding status. Nutrients 16 , 1876 (2024). Kalejahi, P., Kheirouri, S. & Noorazar, S. G. A randomized controlled trial of vitamin D supplementation in Iranian patients with schizophrenia: effects on serum levels of glycogen synthase kinase-3β and symptom severity. Int. J. Psychiatry Med. 58 , 559-575 (2023). Shahini, N., Jazayeri, S. M. M. Z., Jahanshahi, R. & Charkazi, A. Relationship of serum homocysteine and vitamin D with positive, negative, and extrapyramidal symptoms in schizophrenia: a case-control study in Iran. BMC Psychiatry 22 , 681 (2022). Doumat, G. et al . Association between vitamin D status at 3 years and eosinophilic asthma in 6-year-old children with a history of severe bronchiolitis. Thorax 80 , 180–183 (2025). Shen, C. H. et al. Vitamin D level is inversely related to allergen sensitization for risking atopic dermatitis in early childhood. World Allergy Organ. J. 17 , 100890 (2024). Chen, Y. S. et al . The association of prenatal vitamin D sufficiency with aeroallergen sensitization and allergic rhinitis in early childhood. J. Allergy Clin. Immunol. Pract. 9 , 3788–3796.e3 (2021). Brustad, N. et al . Fish oil and vitamin D in pregnancy for the prevention of early childhood asthma: study protocol for two double-blinded, randomised controlled trials. BMJ Open 14 , e092902 (2024). Idiopathic environmental intolerances. American Academy of Allergy, Asthma and Immunology (AAAAI) Board of Directors. J. Allergy Clin. Immunol. 103 , 36-40 (1999). ACOEM position statement. Multiple chemical sensitivities: idiopathic environmental intolerance. College of Occupational and Environmental Medicine. J. Occup. Environ. Med. 41 , 940-942 (1999). Azuma, K., Uchiyama, I. & Kunugita, N. Potential factors affecting chronic chemical intolerance associated with constitutional predisposition or lifestyle and environment during childhood: from a six-year follow-up study. J. Psychosom. Res. 151 , 110665 (2021). Watai, K. et al. Epidemiological association between multiple chemical sensitivity and birth by caesarean section: a nationwide case-control study. Environ. Health 17 , 89 (2018). Yunus, M. B. Fibromyalgia and overlapping disorders: the unifying concept of central sensitivity syndromes. Semin. Arthritis Rheum. 36 , 339-356 (2007). Cui, X. et al. Evaluation of genetic polymorphisms in patients with multiple chemical sensitivity. PLOS One 8 , e73708 (2013). Molot, J., Sears, M., Marshall, L. M. & Bray, R. I. Neurological susceptibility to environmental exposures: pathophysiological mechanisms in neurodegeneration and multiple chemical sensitivity. Rev. Environ. Health 37 , 509-530 (2022). Miyamoto, H. et al . Determination of a serum 25-hydroxyvitamin D reference ranges in Japanese adults using fully automated liquid chromatography-tandem mass spectrometry. J. Nutr. 153 , 1253-1264 (2023). Okazaki, R. et al . Assessment criteria for vitamin D deficiency/insufficiency in Japan: proposal by an expert panel supported by the Research Program of Intractable Diseases, Ministry of Health, Labour and Welfare, Japan, the Japanese Society for Bone and Mineral Research and the Japan Endocrine Society [Opinion]. J. Bone Miner. Metab. 35 , 1-5 (2017). Hossein-Nezhad, A. & Holick, M. F. Vitamin D for health: a global perspective. Mayo Clin. Proc. 88 , 720-755 (2013). Miller, C. S. & Prihoda, T. J. The Environmental Exposure and Sensitivity Inventory (EESI): a standardized approach for measuring chemical intolerances for research and clinical applications. Toxicol. Ind. Health 15 , 370-385 (1999). Hojo, S., Kumano, H., Yoshino, H., Kakuta, K. & Ishikawa, S. Application of Quick Environment Exposure Sensitivity Inventory (QEESI) for Japanese population: study of reliability and validity of the questionnaire. Toxicol. Ind. Health 19 , 41-49 (2003). Schnakenberg, E. et al . A cross-sectional study of self-reported chemical-related sensitivity is associated with gene variants of drug-metabolizing enzymes. Environ. Health 6 , 6 (2007). Skovbjerg, S., Berg, N. D., Elberling, J. & Christensen, K. B. Evaluation of the quick environmental exposure and sensitivity inventory in a Danish population. J. Environ. Public Health 2012 , 304314 (2012). Ono, Y. et al . Seasonal changes of serum 25-hydroxyvitamin D and intact parathyroid hormone levels in a normal Japanese population. J. Bone Miner. Metab. 23 , 147-151 (2005). Weng, F. L., Shults, J., Leonard, M. B., Stallings, V. A. & Zemel, B. S. Risk factors for low serum 25-hydroxyvitamin D concentrations in otherwise healthy children and adolescents. Am. J. Clin. Nutr. 86 , 150-158 (2007). Tardelli, V. S., Lago, M. P. P. D., Silveira, D. X. D. & Fidalgo, T. M. Vitamin D and alcohol: a review of the current literature. Psychiatry Res. 248 , 83-86 (2017). Yang, L. et al . Smoking behavior and circulating vitamin D levels in adults: A meta-analysis. Food Sci. Nutr. 9 , 5820-5832 (2021). Hejazi, E., Amani, R., SharafodinZadeh, N. & Cheraghian, B. Comparison of antioxidant status and vitamin D levels between multiple sclerosis patients and healthy matched subjects. Mult. Scler. Int. 2014 , 539854 (2014). Shaygannejad, V., Golabchi, K., Haghighi, S., Dehghan, H. & Moshayedi, A. A comparative study of 25 (OH) vitamin D serum levels in Patients with Multiple Sclerosis and Control Group in Isfahan, Iran. Int. J. Prev. Med. 1 , 195-201 (2010). Lin, J., Liu, J., Davies, M. L. & Chen, W. Serum vitamin D level and rheumatoid arthritis disease activity: review and meta-analysis. PLOS One 11 , e0146351 (2016). Patel, S. et al. Association between serum vitamin D metabolite levels and disease activity in patients with early inflammatory polyarthritis. Arthritis Rheum. 56 , 2143-2149 (2007). Zhao, S., Duffield, S. J., Moots, R. J. & Goodson, N. J. Systematic review of association between vitamin D levels and susceptibility and disease activity of ankylosing spondylitis. Rheumatol. (Oxf. Engl.) 53 , 1595-1603 (2014). Khabbazi, A., Ghojazadeh, M., Hajebrahimi, S. & Nikniaz, Z. Relationship between vitamin D level and Bechcet’s disease activity: A systematic review and meta-analysis. Int. J. Vitam. Nutr. Res. 90 , 527-534 (2020). Reijven, P. L. M. & Soeters, P. B. Vitamin D: A magic bullet or a myth? Clin. Nutr. 39 , 2663-2674 (2020). Rebelos, E., Tentolouris, N. & Jude, E. The role of vitamin D in health and disease: A narrative review on the mechanisms linking vitamin D with disease and the effects of supplementation. Drugs 83 , 665-685 (2023). Spedding, S., Vanlint, S., Morris, H. & Scragg, R. Does vitamin D sufficiency equate to a single serum 25-hydroxyvitamin D level or are different levels required for non-skeletal diseases? Nutrients 5 , 5127-5139 (2013). Kimlin, M. G. et al . The contributions of solar ultraviolet radiation exposure and other determinants to serum 25-hydroxyvitamin D concentrations in Australian adults: The AusD study. Am. J. Epidemiol. 179 , 864-874 (2014). Nair-Shalliker, V., Clements, M., Fenech, M. & Armstrong, B. K. Personal sun exposure and serum 25-hydroxy vitamin D concentrations. Photochem. Photobiol. 89 , 208-214 (2013). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 17 Mar, 2026 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 16 Oct, 2025 Reviews received at journal 15 Oct, 2025 Reviews received at journal 13 Oct, 2025 Reviews received at journal 10 Oct, 2025 Reviewers agreed at journal 10 Oct, 2025 Reviewers agreed at journal 10 Oct, 2025 Reviews received at journal 09 Oct, 2025 Reviewers agreed at journal 08 Oct, 2025 Reviewers agreed at journal 08 Oct, 2025 Reviewers agreed at journal 08 Oct, 2025 Reviewers invited by journal 08 Oct, 2025 Editor assigned by journal 07 Oct, 2025 Editor invited by journal 23 Sep, 2025 Submission checks completed at journal 05 Sep, 2025 First submitted to journal 05 Sep, 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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Watai","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+UlEQVRIiWNgGAWjYLCChAogcYCN4QADGwMPWEQCr3pmoJYzJGthbINoYWBgI8JNBsfPH/zwcN42Ob4DbImHC8rsZBjYDz9gsNyBR8uZZGaJxG23jSUPsB04PONcMg8DT5oBg+QZ3FrMDiQzgLQkbjjA3nCYt40Z6JccBgbJNjxazj9m/pE453Y9VEs9DwP/GwJabiSzSSQ23E4wADmMt+0wD4MEAVvsbzw2s0g4dttw5mG2hMM8547zsEk8MziAzy+S/YmPb/6ouS3Pd7zN+DNPWbU9P3/yw8eSeEIMAZihNChqDks2EKMFGTB+JFnLKBgFo2AUDGMAANjUUbpAcVgTAAAAAElFTkSuQmCC","orcid":"","institution":"Kindai University Faculty of Medicine","correspondingAuthor":true,"prefix":"","firstName":"Kentaro","middleName":"","lastName":"Watai","suffix":""},{"id":530698207,"identity":"f3164039-7f40-4d98-8029-20842dfd519e","order_by":1,"name":"Sae Ochi","email":"","orcid":"","institution":"The Jikei University School of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Sae","middleName":"","lastName":"Ochi","suffix":""},{"id":530698209,"identity":"d5e40900-891a-43bc-97c9-4d7a1999f7b5","order_by":2,"name":"Tomokazu Matsuura","email":"","orcid":"","institution":"The Jikei University School of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Tomokazu","middleName":"","lastName":"Matsuura","suffix":""},{"id":530698211,"identity":"c46ca6ed-a69f-449f-aca9-9ede22d67cc0","order_by":3,"name":"Kenichi Azuma","email":"","orcid":"","institution":"Kindai University Faculty of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Kenichi","middleName":"","lastName":"Azuma","suffix":""}],"badges":[],"createdAt":"2025-09-03 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14:24:47","extension":"html","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":102728,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7525214/v1/7f4aec78b9192f5180114b25.html"},{"id":93949177,"identity":"f5f351f2-e666-4c44-9c9c-ba02ad2b615b","added_by":"auto","created_at":"2025-10-20 14:40:46","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":134112,"visible":true,"origin":"","legend":"\u003cp\u003eAdjusted means of serum 25(OH)D (ng/mL) by group with 95% confidence intervals (BCa bootstrap, 1,000 resamples). Bootstrap p-value for adjusted difference: 0.119. BCa, bias-corrected and accelerated bootstrap confidence interval\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-7525214/v1/f406c8036ee62164a3e7bb67.png"},{"id":105223398,"identity":"f423233a-5b7c-45e6-9e29-24dc7639c07c","added_by":"auto","created_at":"2026-03-23 16:05:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1041803,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7525214/v1/d4636898-acc0-49dc-96a0-3a307d3b33f3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Comparison of serum 25-hydroxyvitamin D levels between patients with multiple chemical sensitivity and healthy controls: A case–control study","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eVitamin D deficiency is associated with bone-related diseases as well as neurological dysregulation such as multiple sclerosis, mood disorders, and schizophrenia [\u003cspan additionalcitationids=\"CR2 CR3 CR4 CR5\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Furthermore, vitamin D deficiency is associated with allergic diseases such as asthma, atopic dermatitis, and allergic rhinitis [\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. This evidence suggests the possibility that vitamin D plays a role in neurological and allergic diseases. Multiple chemical sensitivity (MCS) shares the same aspects as neurological and allergic diseases. In terms of hypersensitivity, MCS is a disorder characterized by reactions to trace amounts of chemicals or environmental agents that healthy people do not react to, causing multisystem symptoms such as headache, dizziness, cough, and abdominal pain [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Additionally, MCS frequently co-occurs with allergic diseases such as allergic rhinitis [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. From a neurological standpoint, MCS is a type of central sensitization syndrome in which brain or nerve hypersensitivity is thought to be involved [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Considering the immunological and neurological aspects of vitamin D and MCS, it is important to clarify whether vitamin D is involved in the development of MCS. Although the association between vitamin D and MCS has been discussed from a neurological perspective [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], a direct comparison of serum 25-hydroxyvitamin D (25[OH]D) levels between healthy individuals and individuals with MCS has not been reported. To this end, we aimed to compare the serum 25(OH)D status of MCS patients compared with that of healthy controls.\u003c/p\u003e"},{"header":"2. Material and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Study design\u003c/h2\u003e\u003cp\u003eIn this case-control study, we included consecutive female patients diagnosed with MCS at the Immunology and Allergy Center of Shona Kamakura General Hospital between April 2023 and April 2024 as the MSC group. For the control group, we included all consecutive individuals who underwent routine medical examinations at the Centre for Preventive Medicine, Jikei University School of Medicine, and the Toriton Clinic of Jikei University Hospital in Tokyo between April 2019 and March 2020, excluding December 2019 and whose 25(OH)D levels were determined in a previous study [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The case group (n\u0026thinsp;=\u0026thinsp;80) and the control group (n\u0026thinsp;=\u0026thinsp;5,518) were recruited from geographically adjacent areas (Tokyo and Kanagawa) located at similar latitudes to minimize differences in environmental UV exposure.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Method for measuring serum 25 (OH) D\u003c/h2\u003e\u003cp\u003eSerum 25(OH)D levels in the case groups were measured using an electrochemiluminescence immunoassay (ECLIA). For the control group, 25(OH)D levels were determined using a fully automated LC-MS/MS platform consisting of the CLAM-2030 sample preparation module and the LCMS-8050 triple quadrupole mass spectrometer (both from Shimadzu Corporation). The correlation between ECLIA and LC-MS/MS methods has been verified in a previous study [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] (r\u0026thinsp;=\u0026thinsp;0.949), and the equation used to determine this correlation is as follows: ( y [ECLIA]\u0026thinsp;=\u0026thinsp;1.000\u0026times;[LC-MS/MS]\u0026thinsp;+\u0026thinsp;0.850). As such, serum 25(OH)D levels of the two groups were compared based on their ECLIA values.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Classification of 25(OH)D levels\u003c/h2\u003e\u003cp\u003eLevels of 25(OH)D were classified as follows: sufficient (\u0026ge;\u0026thinsp;30 ng/mL), insufficient (20\u0026ndash;29.9 ng/mL), and deficient (\u0026lt;\u0026thinsp;20 ng/mL) [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Diagnosis of multiple chemical sensitivity\u003c/h2\u003e\u003cp\u003eThe Quick Environmental Exposure and Sensitivity Inventory (QEESI) is a commonly utilized questionnaire with demonstrated high diagnostic accuracy for identifying multiple chemical sensitivity (MCS), exhibiting a sensitivity of 92% and specificity of 95% [\u003cspan additionalcitationids=\"CR22 CR23\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. This tool has been applied in MCS research across several countries, including the United States, Japan, and Germany. A validated Japanese version of the QEESI is also available [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The instrument comprises five distinct domains: (1) chemical exposures, (2) other exposures, (3) symptoms, (4) masking index, and (5) impact of sensitivity. All sections, except the masking index, are scored on a 0\u0026ndash;100 scale. Additionally, risk stratification criteria are applied to the chemical exposure (1), symptoms (3), and masking index (4) sections. Individuals scoring 40 points or more in both the chemical exposure and symptoms domains are categorized as \u0026ldquo;highly suggestive\u0026rdquo; of MCS, a criterion employed for participant selection in this study. Further methodological details are outlined below.\u003c/p\u003e\u003cp\u003eThe QEESI is a self-reported assessment tool that captures individuals\u0026rsquo; reactions to various environmental exposures, such as chemicals, food items, skin contactants, alcohol, and caffeine. Each of the first three scales \u0026mdash; Chemical Exposures, Other Exposures, and Symptoms \u0026mdash; comprises 10 items. Respondents rate their responses on a scale from 0 (no reaction) to 10 (severe reaction), based on symptom severity. The development and psychometric validation of these scales, including their sensitivity and specificity, have been described in earlier studies.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Chemical exposures scale (1)\u003c/h2\u003e\u003cp\u003eThis domain evaluates participants\u0026rsquo; sensitivity to ten diverse airborne substances. Participants assign a severity score from 0 to 10 for each item, which includes exposures such as exhaust from diesel or gasoline engines, tobacco smoke, pesticides, gasoline fumes, paints and thinners, scented products, cleaning agents, fresh asphalt or tar, nail products, hair spray, and new furniture.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6. Symptoms scale (3)\u003c/h2\u003e\u003cp\u003eThis domain assesses a broad range of symptom categories, including head-related, musculoskeletal, respiratory and mucosal, cardiovascular, neuromuscular, gastrointestinal, cognitive, emotional, dermatologic, and genitourinary symptoms. Participants rate each symptom based on severity, where 0 indicates no symptoms, 5 indicates moderate symptoms, and 10 indicates severe or disabling symptoms. The total score for this scale ranges from 0 to 100, calculated by summing the scores of all 10 items.\u003c/p\u003e\u003cp\u003eTo enhance the accuracy of case identification, both the QEESI criteria and physician-confirmed diagnoses were employed in determining MCS status among participants.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.7. Statistical analysis\u003c/h2\u003e\u003cp\u003eBecause serum 25(OH)D levels are influenced by demographic and lifestyle factors such as age, sex, season of blood collection, smoking status, body mass index, alcohol intake, and physical activity [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan additionalcitationids=\"CR26\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], these variables were included as covariates in the general linear model with bias-corrected and accelerated bootstrap resampling. The distribution of serum 25(OH)D levels exhibited a slight leftward shift of the peak, resembling a log-normal distribution with noticeable deviation in skewness from a normal distribution. Therefore, bias-corrected and accelerated (BCa) bootstrap resampling was employed, given its robustness in handling skewed data with SPSS software (version 30; IBM Corp, Armonk, NY, USA). A p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e2.8. Ethics approval\u003c/h2\u003e\u003cp\u003eThe central ethics committee of Tokusyukai approved the study protocol (No. TGE02540-024). All methods were performed in accordance with the relevant guidelines and regulations, including the Declaration of Helsinki and the Ethical Guidelines for Medical and Health Research Involving Human Subjects in Japan. For the case group, an opt-out approach was employed in accordance with these ethical guidelines, while written informed consent for secondary use of data was obtained from all participants in the control group.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eOf 89 individuals included in the MCS cohort during the specified period, 9 individuals were excluded because of supplemental administration of vitamin D during the initial visit. The control group included data from 5,518 individuals; however, their vitamin D supplement administration was unknown. In European countries and the United States, people actively consume vitamin D through supplements, and 25(OH)D₂ is often added to foods; therefore, the 25(OH)D₂ concentrations detected in populations in these regions are higher than those observed in the Japanese study [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In the data of controls, the 25(OH)D₂ levels in most participants were below the detection limit, suggesting that vitamin D supplements are not commonly used in this control group [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Therefore, in total, 80 cases and 5,518 controls were included in the analysis.\u003c/p\u003e\u003cp\u003eWe found that 78.8% of the individuals in the MCS group had vitamin D deficiency, and no significant difference was observed when compared with the rate in the control group (75.3%; Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The serum 25(OH)D levels of the MCS group (measured by ECLIA) were not significantly different from that of the control group after conversion of LC-MS/MS values to ECLIA values [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] (median [interquartile range]: 14.6 [11.8\u0026ndash;19.4] vs. 15.6 [12.0\u0026ndash;20.0] ng/mL, p\u0026thinsp;=\u0026thinsp;0.622]; Table. 1). The adjusted analysis using a general linear model with bootstrap resampling (1,000 samples) showed no statistically significant difference in serum 25(OH)D₃ levels between the case and control groups after adjusting for sex, measurement season, smoking status, age, BMI, alcohol index, and physical activity (Difference\u0026thinsp;=\u0026thinsp;1.07, 95% CI [BCa]: \u0026minus;0.18 to 2.46, p\u0026thinsp;=\u0026thinsp;0.119; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Among the covariates, sex, age, time of blood sampling, and alcohol index were significant predictors of serum 25(OH)D levels, while BMI and physical activity were not. Smoking showed a borderline effect (p\u0026thinsp;=\u0026thinsp;0.069; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Adjusted means were 17.04 ng/mL (95% CI [BCa]: 15.81\u0026ndash;18.38) for the case group and 15.98 ng/mL (95% CI [BCa]: 15.48\u0026ndash;16.45) for the control group, with an adjusted difference of 1.07 ng/mL (95% CI [BCa]: \u0026minus;0.18 to 2.46, p\u0026thinsp;=\u0026thinsp;0.119; Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\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\u003eDemographics and serum 25(OH)D levels\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\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=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCase group,\u003c/p\u003e\u003cp\u003en\u0026thinsp;=\u0026thinsp;80\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eControl group,\u003c/p\u003e\u003cp\u003en\u0026thinsp;=\u0026thinsp;5,518\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eP value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSex, female/male\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e77/3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2,118/3,400\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\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\u003eAge (years), median (IQR)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e53 (43\u0026ndash;65)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e50 (39\u0026ndash;59)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.005\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime of blood sampling\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\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWinter (January to March), n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e16 (20.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e600 (10.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\" morerows=\"3\" rowspan=\"4\"\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\u003eSpring (April to June), n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e16 (20.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2,800 (50.7)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSummer (July to September), n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14 (17.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2,088 (37.8)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFall (October to December), n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e34 (42.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30 (0.5)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSmoking [Current/ (past +\u0026thinsp;never)]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e597/4921\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0/80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBMI (kg/m\u0026sup2;)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e22.6 (19.8\u0026ndash;25.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.4 (20.3\u0026ndash;24.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.874\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAlcohol index (g/day)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 (0\u0026ndash;137)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\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\u003ePhysical activity (min/day)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0\u0026ndash;0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30 (0\u0026ndash;60)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\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\u003eLevels of 25-hydroxyvitamin D\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\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e25(OH)D, median (IQR), (ng/mL)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14.6 (11.8\u0026ndash;19.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e15.6 (12.0\u0026ndash;20.0)\u003csup\u003e\u0026dagger;\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.622\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSufficient as \u0026ge;\u0026thinsp;30 ng/mL, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2 (2.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e145 (2.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e0.765\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eInsufficiency as 20\u0026ndash;29.9 ng/mL, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e15 (18.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1,220 (22.1)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDeficiency as \u0026lt;\u0026thinsp;20 ng/mL, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e63 (78.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4,153 (75.3)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eIQR, interquartile range; 25-hydroxyvitamin D, 25(OH)D\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003e\u0026dagger; The values of the control group are adjusted values calculated using the following formula. The correlation between ECLIA and LC-MS/MS methods has been verified in the previous studiy\u003csup\u003e6\u003c/sup\u003e, r\u0026thinsp;=\u0026thinsp;0.949 (P\u0026thinsp;\u0026lt;\u0026thinsp;0.01), and the equation describing this correlation is y (ECLIA)\u0026thinsp;=\u0026thinsp;1.000 x (LC-MS/MS)\u0026thinsp;+\u0026thinsp;0.850.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\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\u003eGeneral Linear Model with Bootstrap\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" 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=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariables\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eB (Estimate)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95% CI (BCa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBootstrap p-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGroup (Ref. control)\u003c/p\u003e\u003cp\u003eCase\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026minus;0.18 to 2.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.119\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSex (Ref. female)\u003c/p\u003e\u003cp\u003eMale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.77 to 2.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAge (year)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.077\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.064 to 0.088\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTime of blood sampling\u003c/p\u003e\u003cp\u003e[Ref. Winter (Jan to Mar)]\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\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpring (Apr to Jun)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.93 to 1.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSummer (Jul to Sep)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.62 to 1.69\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFall (Oct to Dec)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026minus;1.11 to 2.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.448\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSmoking (Ref. Current)\u003c/p\u003e\u003cp\u003eOthers (past +\u0026thinsp;never)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e\u0026minus;0.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026minus;1.14 to 0.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.069\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBMI (kg/m\u0026sup2;)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e\u0026minus;0.033\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026minus;0.080 to 0.012\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.160\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAlcohol index\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.000 to 0.002\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.014\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePhysical activity (min/day)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e\u0026minus;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026minus;0.003 to 0.002\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.679\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eDependent variable: Serum 25(OH)D, ng/mL\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eBCa, bias-corrected and accelerated bootstrap confidence interval (1,000 resamples)\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eAdjusted Means of Serum 25(OH)D by Group\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAdjusted Mean (ng/mL)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e95% CI (BCa)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCase\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e17.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e15.81 to 18.38\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eControl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e15.98\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e15.48 to 16.45\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDifference (Case \u0026ndash; Control)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026minus;0.18 to 2.46\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"3\"\u003eBootstrap p-value for adjusted difference: 0.119 (not significant).\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"3\"\u003eBCa, bias-corrected and accelerated bootstrap confidence interval (1,000 resamples)\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e4.1. Comparison of 25(OH)D levels between MCS patients and healthy controls\u003c/h2\u003e\u003cp\u003eTo our knowledge, this is the first study to compare 25(OH)D levels between patients with MCS and healthy controls. We found that although a high percentage of patients with MCS (78.8%) had vitamin D deficiency, an adjusted analysis using a general linear model with bootstrap resampling revealed no significant difference in 25(OH)D levels between patients with MCS and healthy controls. Our findings indicate that sex, age, and seasonal variation were observed to be associated with vitamin D status, whereas BMI and physical activity were not significant predictors. Interestingly, alcohol intake showed a modest positive association with serum 25(OH)D₃, while current smoking exhibited a borderline negative association. These results are consistent with previous reports highlighting the influence of seasonal sunlight exposure and age-related metabolic changes on vitamin D levels [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The lack of a significant group effect suggests that the observed differences in vitamin D status may primarily reflect demographic and behavioral factors rather than disease status itself.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e4.2. Contradictory findings in previous studies\u003c/h2\u003e\u003cp\u003eIn a previous study, vitamin D levels in patients with multiple sclerosis show no significant difference compared to that of healthy controls, with both groups exhibiting low levels [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. However, another study revealed significant differences, yielding contradictory results [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. These discrepancies may be because 25(OH)D levels can vary depending on measurement conditions, such as age, sex, and seasonal variations in UV exposure[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Therefore, in this study, analyses were adjusted for sex, age, season of blood collection, smoking status, body mass index, alcohol consumption, and physical activity. Moreover, the hospitals attended by the patient and control groups were in nearby areas, and the climate and the number of hours of sunlight were approximately the same.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e4.3. Potential role of vitamin D in inflammatory diseases\u003c/h2\u003e\u003cp\u003eResearch has suggested an inverse relationship between 25(OD)D levels and disease activity under various inflammatory conditions. Patients with rheumatoid arthritis have lower vitamin D levels than healthy controls, with a negative correlation between serum 25(OH)D levels and disease severity [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Similarly, in early inflammatory polyarthritis, higher 25(OH)D levels are associated with lower disease activity and C-reactive protein levels [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. For ankylosing spondylitis, cross-sectional studies have indicated lower vitamin D levels in patients than in controls, with some evidence of an inverse correlation between 25(OH)D and disease activity [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Active patients with Beh\u0026ccedil;et\u0026rsquo;s disease have significantly lower serum 25(OH)D levels than healthy controls and inactive patients [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. These findings suggest a potential immunomodulatory role of vitamin D in inflammatory diseases, although longitudinal studies are needed to establish causality. While the relationship between MCS severity and serum 25(OH)D level is also interesting, we did not assess this relationship in this study. Notably, the assessment of MCS severity is subjective, as there are currently no established objective markers.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e4.4. Uncertainty in the effectiveness of Vitamin D supplementation\u003c/h2\u003e\u003cp\u003eTo date, the results of randomized controlled trials have been inconsistent, and clear evidence of the effects of vitamin D is difficult to achieve [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. With respect to the efficacy of vitamin D supplementation, the minimum effective serum 25(OH)D level is thought to vary with disease. This may be because the cut-off levels of serum 25(OH)D indicating deficiency or sufficiency may be disease-dependent, just as vitamin D metabolism is tissue-dependent [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Therefore, the relationship between vitamin D levels and disease activity remains unclear and may vary by disease. These insights provide important guidance for considering an appropriate approach for vitamin D supplementation therapy.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e4.5. Study limitations\u003c/h2\u003e\u003cp\u003eThis study has several limitations. First, although we adjusted for age, sex, season of blood collection, smoking status, BMI, alcohol consumption, and physical activity, other potential determinants of serum 25(OH)D levels such as dietary intake, comorbid conditions, or genetic polymorphisms were not assessed. Second, sun exposure, which is a major determinant of vitamin D status, was not directly measured in this study. Although previous studies have shown that sun exposure generally influences serum 25(OH)D levels [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e], a study reported no significant association between sun exposure and serum vitamin D in multiple sclerosis patients, while an effect remained in healthy controls [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Therefore, the potential influence of sun exposure on our results cannot be completely excluded. Third, the sample size of the MCS group was relatively small compared to the large control cohort, which may have limited the statistical power to detect subtle differences. Finally, the case\u0026ndash;control design restricts causal inference, and the cross-sectional assessment precludes evaluation of temporal or disease-severity\u0026ndash;related associations between vitamin D status and MCS.\u003c/p\u003e\u003c/div\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eIn this case\u0026ndash;control study, no significant differences in serum 25(OH)D levels were observed between patients with MCS and healthy controls after adjusting for demographic and lifestyle factors. While vitamin D deficiency was prevalent in both groups, our findings suggest that reduced vitamin D levels are unlikely to represent a disease-specific marker of MCS. These results should be interpreted with caution given the observational design and limited case sample size. Future longitudinal and mechanistic studies are warranted to clarify whether vitamin D plays any contributory or modulatory role in the pathophysiology of MCS.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e25(OH)D: 25-hydroxyvitamin D\u003c/p\u003e\n\u003cp\u003eECLIA: electrochemiluminescence immunoassay\u003c/p\u003e\n\u003cp\u003eLC-MS/MS: liquid chromatography-tandem mass spectrometry\u003c/p\u003e\n\u003cp\u003eMCS: multiple chemical sensitivity\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe central ethics committee of Tokusyukai approved the study protocol (No. TGE02540-024).\u0026nbsp;For the case group, an opt-out approach was employed in accordance with ethical guidelines, while written informed consent for secondary use of data was obtained from all participants in the control group.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDue to ethical considerations, the dataset is not publicly available. However, pseudonymized data may be provided by the corresponding author upon a justified request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors declare that they have no conflicts of interest related to this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that this work was carried out independently and did not benefit from any designated funding from public, commercial, or philanthropic sources.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eKW, SO, and TM conceptualized and designed the study. Data collection was carried out by KW, SO, and TM. Statistical analyses were performed by KW and KA. Data interpretation involved contributions from KW, SO, and TM. The manuscript was drafted by KW, with KA providing critical revisions. All authors reviewed and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe sincerely thank all patients with MCS and healthy control participants for their valuable contribution to this study.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eNakamura, K. \u003cem\u003eet al\u003c/em\u003e. The Murakami Cohort Study of vitamin D for the prevention of musculoskeletal and other age-related diseases: a study protocol. \u003cem\u003eEnviron. Health Prev. Med.\u003c/em\u003e \u003cstrong\u003e23\u003c/strong\u003e, 28 (2018).\u003c/li\u003e\n\u003cli\u003eYu, X. H. \u003cem\u003eet al.\u003c/em\u003e Association between 25(OH) vitamin D and multiple sclerosis: cohort, shared genetics, and Causality. \u003cem\u003eNutr. J.\u003c/em\u003e \u003cstrong\u003e23\u003c/strong\u003e, 151 (2024).\u003c/li\u003e\n\u003cli\u003eAlelyani, M. \u003cem\u003eet al\u003c/em\u003e. Assessment of vitamin D status and associated risk factors in high-altitude populations affected by multiple sclerosis: A case-control study. \u003cem\u003eMedicine\u003c/em\u003e \u003cstrong\u003e103\u003c/strong\u003e, e38369 (2024).\u003c/li\u003e\n\u003cli\u003eHollinshead, V. R. B. B., Piaskowski, J. L. \u0026amp; Chen, Y. Low vitamin D concentration is associated with increased depression risk in adults 20-44 years old, an NHANES 2007-2018 data analysis with a focus on perinatal and breastfeeding status. \u003cem\u003eNutrients\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 1876 (2024).\u003c/li\u003e\n\u003cli\u003eKalejahi, P., Kheirouri, S. \u0026amp; Noorazar, S. G. A randomized controlled trial of vitamin D supplementation in Iranian patients with schizophrenia: effects on serum levels of glycogen synthase kinase-3\u0026beta; and symptom severity. \u003cem\u003eInt. J. Psychiatry Med.\u003c/em\u003e \u003cstrong\u003e58\u003c/strong\u003e, 559-575 (2023).\u003c/li\u003e\n\u003cli\u003eShahini, N., Jazayeri, S. M. M. Z., Jahanshahi, R. \u0026amp; Charkazi, A. Relationship of serum homocysteine and vitamin D with positive, negative, and extrapyramidal symptoms in schizophrenia: a case-control study in Iran. \u003cem\u003eBMC Psychiatry\u003c/em\u003e \u003cstrong\u003e22\u003c/strong\u003e, 681 (2022).\u003c/li\u003e\n\u003cli\u003eDoumat, G. \u003cem\u003eet al\u003c/em\u003e. Association between vitamin D status at 3 years and eosinophilic asthma in 6-year-old children with a history of severe bronchiolitis. \u003cem\u003eThorax\u003c/em\u003e \u003cstrong\u003e80\u003c/strong\u003e, 180\u0026ndash;183 (2025).\u003c/li\u003e\n\u003cli\u003eShen, C. H. \u003cem\u003eet al.\u003c/em\u003e Vitamin D level is inversely related to allergen sensitization for risking atopic dermatitis in early childhood. \u003cem\u003eWorld Allergy Organ. J.\u003c/em\u003e \u003cstrong\u003e17\u003c/strong\u003e, 100890 (2024).\u003c/li\u003e\n\u003cli\u003eChen, Y. S. \u003cem\u003eet al\u003c/em\u003e. The association of prenatal vitamin D sufficiency with aeroallergen sensitization and allergic rhinitis in early childhood. \u003cem\u003eJ. Allergy Clin. Immunol. Pract.\u003c/em\u003e \u003cstrong\u003e9\u003c/strong\u003e, 3788\u0026ndash;3796.e3 (2021).\u003c/li\u003e\n\u003cli\u003eBrustad, N. \u003cem\u003eet al\u003c/em\u003e. Fish oil and vitamin D in pregnancy for the prevention of early childhood asthma: study protocol for two double-blinded, randomised controlled trials. \u003cem\u003eBMJ Open\u003c/em\u003e \u003cstrong\u003e14\u003c/strong\u003e, e092902 (2024).\u003c/li\u003e\n\u003cli\u003eIdiopathic environmental intolerances. American Academy of Allergy, Asthma and Immunology (AAAAI) Board of Directors. \u003cem\u003eJ. Allergy Clin. Immunol.\u003c/em\u003e \u003cstrong\u003e103\u003c/strong\u003e, 36-40 (1999).\u003c/li\u003e\n\u003cli\u003eACOEM position statement. Multiple chemical sensitivities: idiopathic environmental intolerance. College of Occupational and Environmental Medicine. \u003cem\u003eJ. Occup. Environ. Med.\u003c/em\u003e \u003cstrong\u003e41\u003c/strong\u003e, 940-942 (1999).\u003c/li\u003e\n\u003cli\u003eAzuma, K., Uchiyama, I. \u0026amp; Kunugita, N. Potential factors affecting chronic chemical intolerance associated with constitutional predisposition or lifestyle and environment during childhood: from a six-year follow-up study. \u003cem\u003eJ. Psychosom. Res.\u003c/em\u003e \u003cstrong\u003e151\u003c/strong\u003e, 110665 (2021).\u003c/li\u003e\n\u003cli\u003eWatai, K. \u003cem\u003eet al.\u003c/em\u003e Epidemiological association between multiple chemical sensitivity and birth by caesarean section: a nationwide case-control study. \u003cem\u003eEnviron. Health\u003c/em\u003e \u003cstrong\u003e17\u003c/strong\u003e, 89 (2018).\u003c/li\u003e\n\u003cli\u003eYunus, M. B. Fibromyalgia and overlapping disorders: the unifying concept of central sensitivity syndromes. \u003cem\u003eSemin. Arthritis Rheum.\u003c/em\u003e \u003cstrong\u003e36\u003c/strong\u003e, 339-356 (2007).\u003c/li\u003e\n\u003cli\u003eCui, X. \u003cem\u003eet al.\u003c/em\u003e Evaluation of genetic polymorphisms in patients with multiple chemical sensitivity. \u003cem\u003ePLOS One\u003c/em\u003e \u003cstrong\u003e8\u003c/strong\u003e, e73708 (2013).\u003c/li\u003e\n\u003cli\u003eMolot, J., Sears, M., Marshall, L. M. \u0026amp; Bray, R. I. Neurological susceptibility to environmental exposures: pathophysiological mechanisms in neurodegeneration and multiple chemical sensitivity. \u003cem\u003eRev. Environ. Health\u003c/em\u003e \u003cstrong\u003e37\u003c/strong\u003e, 509-530 (2022).\u003c/li\u003e\n\u003cli\u003eMiyamoto, H. \u003cem\u003eet al\u003c/em\u003e. Determination of a serum 25-hydroxyvitamin D reference ranges in Japanese adults using fully automated liquid chromatography-tandem mass spectrometry. \u003cem\u003eJ. Nutr.\u003c/em\u003e \u003cstrong\u003e153\u003c/strong\u003e, 1253-1264 (2023).\u003c/li\u003e\n\u003cli\u003eOkazaki, R. \u003cem\u003eet al\u003c/em\u003e. Assessment criteria for vitamin D deficiency/insufficiency in Japan: proposal by an expert panel supported by the Research Program of Intractable Diseases, Ministry of Health, Labour and Welfare, Japan, the Japanese Society for Bone and Mineral Research and the Japan Endocrine Society [Opinion]. \u003cem\u003eJ. Bone Miner. Metab.\u003c/em\u003e \u003cstrong\u003e35\u003c/strong\u003e, 1-5 (2017).\u003c/li\u003e\n\u003cli\u003eHossein-Nezhad, A. \u0026amp; Holick, M. F. Vitamin D for health: a global perspective. \u003cem\u003eMayo Clin. Proc.\u003c/em\u003e \u003cstrong\u003e88\u003c/strong\u003e, 720-755 (2013).\u003c/li\u003e\n\u003cli\u003eMiller, C. S. \u0026amp; Prihoda, T. J. The Environmental Exposure and Sensitivity Inventory (EESI): a standardized approach for measuring chemical intolerances for research and clinical applications. \u003cem\u003eToxicol. Ind. Health\u003c/em\u003e \u003cstrong\u003e15\u003c/strong\u003e, 370-385 (1999).\u003c/li\u003e\n\u003cli\u003eHojo, S., Kumano, H., Yoshino, H., Kakuta, K. \u0026amp; Ishikawa, S. Application of Quick Environment Exposure Sensitivity Inventory (QEESI) for Japanese population: study of reliability and validity of the questionnaire. \u003cem\u003eToxicol. Ind. Health\u003c/em\u003e \u003cstrong\u003e19\u003c/strong\u003e, 41-49 (2003).\u003c/li\u003e\n\u003cli\u003eSchnakenberg, E. \u003cem\u003eet al\u003c/em\u003e. A cross-sectional study of self-reported chemical-related sensitivity is associated with gene variants of drug-metabolizing enzymes. \u003cem\u003eEnviron. Health\u003c/em\u003e \u003cstrong\u003e6\u003c/strong\u003e, 6 (2007).\u003c/li\u003e\n\u003cli\u003eSkovbjerg, S., Berg, N. D., Elberling, J. \u0026amp; Christensen, K. B. Evaluation of the quick environmental exposure and sensitivity inventory in a Danish population. \u003cem\u003eJ. Environ. Public Health\u003c/em\u003e \u003cstrong\u003e2012\u003c/strong\u003e, 304314 (2012).\u003c/li\u003e\n\u003cli\u003eOno, Y. \u003cem\u003eet al\u003c/em\u003e. Seasonal changes of serum 25-hydroxyvitamin D and intact parathyroid hormone levels in a normal Japanese population. \u003cem\u003eJ. Bone Miner. Metab.\u003c/em\u003e \u003cstrong\u003e23\u003c/strong\u003e, 147-151 (2005).\u003c/li\u003e\n\u003cli\u003eWeng, F. L., Shults, J., Leonard, M. B., Stallings, V. A. \u0026amp; Zemel, B. S. Risk factors for low serum 25-hydroxyvitamin D concentrations in otherwise healthy children and adolescents. \u003cem\u003eAm. J. Clin. Nutr.\u003c/em\u003e \u003cstrong\u003e86\u003c/strong\u003e, 150-158 (2007).\u003c/li\u003e\n\u003cli\u003eTardelli, V. S., Lago, M. P. P. D., Silveira, D. X. D. \u0026amp; Fidalgo, T. M. Vitamin D and alcohol: a review of the current literature. \u003cem\u003ePsychiatry Res.\u003c/em\u003e \u003cstrong\u003e248\u003c/strong\u003e, 83-86 (2017).\u003c/li\u003e\n\u003cli\u003eYang, L. \u003cem\u003eet al\u003c/em\u003e. Smoking behavior and circulating vitamin D levels in adults: A meta-analysis. \u003cem\u003eFood Sci. Nutr.\u003c/em\u003e \u003cstrong\u003e9\u003c/strong\u003e, 5820-5832 (2021).\u003c/li\u003e\n\u003cli\u003eHejazi, E., Amani, R., SharafodinZadeh, N. \u0026amp; Cheraghian, B. Comparison of antioxidant status and vitamin D levels between multiple sclerosis patients and healthy matched subjects. \u003cem\u003eMult. Scler. Int.\u003c/em\u003e \u003cstrong\u003e2014\u003c/strong\u003e, 539854 (2014).\u003c/li\u003e\n\u003cli\u003eShaygannejad, V., Golabchi, K., Haghighi, S., Dehghan, H. \u0026amp; Moshayedi, A. A comparative study of 25 (OH) vitamin D serum levels in Patients with Multiple Sclerosis and Control Group in Isfahan, Iran. \u003cem\u003eInt. J. Prev. Med.\u003c/em\u003e \u003cstrong\u003e1\u003c/strong\u003e, 195-201 (2010).\u003c/li\u003e\n\u003cli\u003eLin, J., Liu, J., Davies, M. L. \u0026amp; Chen, W. Serum vitamin D level and rheumatoid arthritis disease activity: review and meta-analysis. \u003cem\u003ePLOS One\u003c/em\u003e \u003cstrong\u003e11\u003c/strong\u003e, e0146351 (2016).\u003c/li\u003e\n\u003cli\u003ePatel, S. \u003cem\u003eet al.\u003c/em\u003e Association between serum vitamin D metabolite levels and disease activity in patients with early inflammatory polyarthritis. \u003cem\u003eArthritis Rheum.\u003c/em\u003e \u003cstrong\u003e56\u003c/strong\u003e, 2143-2149 (2007).\u003c/li\u003e\n\u003cli\u003eZhao, S., Duffield, S. J., Moots, R. J. \u0026amp; Goodson, N. J. Systematic review of association between vitamin D levels and susceptibility and disease activity of ankylosing spondylitis. \u003cem\u003eRheumatol. (Oxf. Engl.)\u003c/em\u003e \u003cstrong\u003e53\u003c/strong\u003e, 1595-1603 (2014).\u003c/li\u003e\n\u003cli\u003eKhabbazi, A., Ghojazadeh, M., Hajebrahimi, S. \u0026amp; Nikniaz, Z. Relationship between vitamin D level and Bechcet\u0026rsquo;s disease activity: A systematic review and meta-analysis. \u003cem\u003eInt. J. Vitam. Nutr. Res.\u003c/em\u003e \u003cstrong\u003e90\u003c/strong\u003e, 527-534 (2020).\u003c/li\u003e\n\u003cli\u003eReijven, P. L. M. \u0026amp; Soeters, P. B. Vitamin D: A magic bullet or a myth? \u003cem\u003eClin. Nutr.\u003c/em\u003e \u003cstrong\u003e39\u003c/strong\u003e, 2663-2674 (2020).\u003c/li\u003e\n\u003cli\u003eRebelos, E., Tentolouris, N. \u0026amp; Jude, E. The role of vitamin D in health and disease: A narrative review on the mechanisms linking vitamin D with disease and the effects of supplementation. \u003cem\u003eDrugs\u003c/em\u003e \u003cstrong\u003e83\u003c/strong\u003e, 665-685 (2023).\u003c/li\u003e\n\u003cli\u003eSpedding, S., Vanlint, S., Morris, H. \u0026amp; Scragg, R. Does vitamin D sufficiency equate to a single serum 25-hydroxyvitamin D level or are different levels required for non-skeletal diseases? \u003cem\u003eNutrients\u003c/em\u003e \u003cstrong\u003e5\u003c/strong\u003e, 5127-5139 (2013).\u003c/li\u003e\n\u003cli\u003eKimlin, M. G. \u003cem\u003eet al\u003c/em\u003e. The contributions of solar ultraviolet radiation exposure and other determinants to serum 25-hydroxyvitamin D concentrations in Australian adults: The AusD study. \u003cem\u003eAm. J. Epidemiol.\u003c/em\u003e \u003cstrong\u003e179\u003c/strong\u003e, 864-874 (2014).\u003c/li\u003e\n\u003cli\u003eNair-Shalliker, V., Clements, M., Fenech, M. \u0026amp; Armstrong, B. K. Personal sun exposure and serum 25-hydroxy vitamin D concentrations. \u003cem\u003ePhotochem. Photobiol.\u003c/em\u003e \u003cstrong\u003e89\u003c/strong\u003e, 208-214 (2013).\u003cbr\u003e \u003c/li\u003e\n\u003c/ol\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":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"multiple chemical sensitivity, vitamin D, 25-hydroxyvitamin D","lastPublishedDoi":"10.21203/rs.3.rs-7525214/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7525214/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eVitamin D deficiency has been associated with a range of neurological and allergic conditions. Whether such an association exists in multiple chemical sensitivity (MCS) has not been clarified. This study aimed to compare serum 25-hydroxyvitamin D (25[OH]D) concentrations between patients with MCS and healthy controls. We conducted a case\u0026ndash;control study including 80 female patients with physician-diagnosed MCS and 5,518 controls. Serum 25(OH)D concentrations were compared using a general linear model with bias-corrected and accelerated bootstrap resampling (1,000 iterations), adjusting for age, sex, season of blood collection, smoking status, body mass index, alcohol intake, and physical activity. Vitamin D deficiency (\u0026lt;\u0026thinsp;20 ng/mL) was highly prevalent in both groups (78.8% in MCS vs. 75.3% in controls). Median serum 25(OH)D concentrations did not differ significantly between groups (14.6 vs. 15.6 ng/mL, p\u0026thinsp;=\u0026thinsp;0.622). Adjusted analyses confirmed no statistically significant difference (adjusted difference\u0026thinsp;=\u0026thinsp;1.07 ng/mL, 95% CI: \u0026minus;0.18 to 2.46, p\u0026thinsp;=\u0026thinsp;0.119). Despite the high prevalence of vitamin D deficiency, patients with MCS did not differ significantly from controls in serum 25(OH)D concentrations. These findings indicate that vitamin D status does not distinguish individuals with MCS from the general population. Further longitudinal and mechanistic studies are warranted to clarify the potential relationship between vitamin D and MCS.\u003c/p\u003e","manuscriptTitle":"Comparison of serum 25-hydroxyvitamin D levels between patients with multiple chemical sensitivity and healthy controls: A case–control study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-20 14:24:42","doi":"10.21203/rs.3.rs-7525214/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-16T13:56:01+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-15T20:32:49+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-13T08:40:18+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-10T20:09:54+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"77114654148009745831895833218223773824","date":"2025-10-10T18:33:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"80639705125120902570440566069325530730","date":"2025-10-10T06:26:56+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-09T19:47:44+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"238908729452045197886170566198697664203","date":"2025-10-08T08:41:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"242475846026003545181372980096706578291","date":"2025-10-08T06:59:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"104534782672064424882879921395303831156","date":"2025-10-08T05:28:30+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-08T05:20:20+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-07T11:34:23+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-09-23T14:48:28+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-05T16:17:56+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-09-05T16:15:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f9456e0d-b961-4ef9-a99a-3eae5044f9c0","owner":[],"postedDate":"October 20th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":56418066,"name":"Health sciences/Biomarkers"},{"id":56418067,"name":"Health sciences/Diseases"},{"id":56418068,"name":"Health sciences/Medical research"},{"id":56418069,"name":"Health sciences/Neurology"},{"id":56418070,"name":"Biological sciences/Neuroscience"}],"tags":[],"updatedAt":"2026-03-23T16:02:08+00:00","versionOfRecord":{"articleIdentity":"rs-7525214","link":"https://doi.org/10.1038/s41598-026-44643-w","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2026-03-17 15:58:12","publishedOnDateReadable":"March 17th, 2026"},"versionCreatedAt":"2025-10-20 14:24:42","video":"","vorDoi":"10.1038/s41598-026-44643-w","vorDoiUrl":"https://doi.org/10.1038/s41598-026-44643-w","workflowStages":[]},"version":"v1","identity":"rs-7525214","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7525214","identity":"rs-7525214","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}