Continuous positive airways pressure therapy and cardiovascular dysautonomia among obstructive sleep apnea patients in Yaoundé, Cameroon: a pilot study

Continuous positive airways pressure therapy and cardiovascular dysautonomia among obstructive sleep apnea patients in Yaoundé, Cameroon: a pilot study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Continuous positive airways pressure therapy and cardiovascular dysautonomia among obstructive sleep apnea patients in Yaoundé, Cameroon: a pilot study Massongo Massongo, Amalia Owona Ngadebe, Marie Elisabeth Ngah Komo, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6863517/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Objective We aimed to study the association between cardiovascular dysautonomia and CPAP in patients with obstructive sleep apnea in Yaoundé, Cameroon. Methods From December 2020 to May 2021, we enrolled obstructive sleep apnea patients, treated with CPAP (CPAP+) or not (CPAP-). We assessed cardiovascular dysautonomia using functional tests (deep breathing, stand test and orthostatic hypotension) and heart rate variability (HRV). The latter was studied using the Kubios HRV Standard 3.5.0 software, and included low frequency (LF), high frequency (HF) and LF/ HF ratio. We compared qualitative and quantitative variables between the two patient groups with the Fisher exact and Wilcoxon tests respectively. The significance threshold was set at p < 0.05 . Results We enrolled 8 CPAP + and 11 CPAP-, with median ages (25th, 75th percentiles) 55.5 (52.6, 60.7) and 59 (53.0, 64.0) years respectively. CPAP therapy was associated with LF area (p = 0.033), HF area (p = 0.041) and heart rate difference on deep breathing test (p = 0,006). All patients had at least one feature of cardiovascular dysautonomia. Compared to CPAP+, CPAP- presented a greater proportion of abnormal LF (72.7% vs 25.0%, p = 0.069), HF (63.64% vs 12.5%, p = 0.058), deep breathing (100.0% vs 75.0%, p = 0.163) and stand test (100.0% vs 62.5%, p = 0.058), SNS dysautonomia (72.7% vs 37.5%, p = 0.122) and PNS dysautonomia (100.0% vs 87.5%, p = 0.421). Conclusion In this small sample size pilot study, CPAP + patients presented greater LF and HF powers, and higher average heart rate difference on deep breathing test. Regarding single features, only decreased LF was lower in CPAP + compared to CPAP-. obstructive sleep apnea syndrome continuous positive airway pressure cardiovascular dysautonomia Figures Figure 1 Introduction Obstructive sleep apnea (OSA) is a major public health issue characterized by repetitive episodes of partial or total occlusion of the upper airway during sleep, causing exaggerated effort to breathe against the occluded airway, sleep fragmentation, and intermittent hypoxemia. Clinically relevant obstructive sleep apnea hypopnea syndrome (OSAHS) has a prevalence of 3 to 7% for men and 1 to 4% for women in the general population ( 1 – 4 ), and up to 49.6% in a Cameroonian hospitalized-patients sample ( 5 ). The prevalence of sleep-disordered breathing (SDB), not taking into account the clinical manifestations, is much higher both in community-based studies (40–80% in developed countries, 36% in Cameroon) and hospital-based ones (57.7% in Central Hospital of Yaoundé, Cameroon) ( 6 , 7 ). The effects of OSA during sleep (especially intermittent hypoxia) elicit a number of intermediate mechanisms, including sympathetic activation, endothelial dysfunction, oxidative stress, inflammation, and metabolic dysfunction, which can contribute to increased cardiovascular risk. This has been confirmed by several studies demonstrating the association of OSAHS with a poor cardiovascular outcome ( 8 – 13 ). These cardiovascular disorders can, at least partially, involve a cardiovascular-related autonomic nervous system (ANS) impairment, or cardiovascular dysautonomia (CVD). During obstructive events, hypoxemia and hypercapnia episodes can increase sympathetic tonus and responsiveness, which can contribute to sympatho-vagal imbalance and, in consequence, dysautonomia. The association between OSA and CVD has been widely described in the literature, especially in the past decade ( 14 – 24 ). A few authors have even suggested some features of CVD as tools for OSA screening ( 25 , 26 ). Continuous positive airway pressure (CPAP) is the most efficacious and commonly used treatment for patients with OSA. CPAP treatment has been shown to improve OSA-related symptoms, reduce blood pressure, ameliorate cardiovascular risk, and improve quality of life in severe patients ( 11 , 27 – 29 ). We found a few studies ( 30 – 33 ) and two reviews ( 34 , 35 ) that sought the impact of CPAP on CVD. Their results suggest a positive effect of CPAP. However, none were carried out in Africa. The aim of our study was to search for the association between CPAP therapy and CVD among OSA patients in Cameroon, where OSAHS is still an emerging disease. Methodology Study design and setting This was a hospital-based cross-sectional study from December 2020 to May 2021 at the Polymer Medical Center (PMC) in Yaounde. PMC is a major center for respiratory diseases, including sleep disordered breathing (SDB) and especially OSA, which are an emerging condition in Sub-Saharan Africa (SSA), with limited access to diagnosis, and moreover CPAP therapy. The center receives patients from Yaounde and other regions of Cameroon. A sleep laboratory is present, having both polygraphy and polysomnography. Study population and sampling PMC patients aged at least 30 years old, and who had been diagnosed with OSA at least 6 months ago were invited to participate. Those presenting with motor, behavioral or consciousness disorders were excluded from the sample. We used the sleep laboratory register to identify eligible patients. The eligible ones were invited by phone call or physically as they attended PMC for their follow-up, according to their treatment status. Data collection Data were collected by a 7th year trained medical student both from the patient’s file and during a face-to-face interview during which physical examination and assessment for cardiovascular dysautonomia were done. These were recorded on a pre-prepared data collection form. Baseline data Demographic and habitus : age and sex were recorded as numeric and dichotomic variables respectively. Smoking status was categorized into non-smoker (person not actively smoking and who has smoked < 20 packets of cigarettes during their whole life), smoker (person actively smoking), and ex-smoker (person who has smoked 20 packets or more and has stopped smoking for at least 6 months). Alcohol consumption was divided into consumer and non-consumer (no alcohol consumption in the last 3 months). Drug intake was divided into presence (person taking at least one drug for a chronic condition) and absence (no long-term drug). Comorbid conditions : the presence of cardiovascular comorbidity or risk factor (hypertension, diabetes mellitus, stroke, heart failure) was recorded as a dichotomic variable (presence or absence). Clinical features : weight was measured using a digital wireless scale, and height was measured using a graduated stadiometer. Both allowed the calculation of the body mass index (weight in kg/ height 2 in m 2 ). The latter was then used to define the following weight categories: underweight (< 18.5 kg/m 2 ), normal (18.5–24.9 kg/m 2 ), overweight (25-29.9 kg/m 2 ) and obesity (≥ 30 kg/m 2 ). OSA and CPAP-related data : The apnea-hypopnea index (AHI) was recorded as numeric variable. It was subsequently used to define OSA severity groups as mild (< 15/h), moderate (15–29/h) and severe (≥ 30/h). CPAP therapy status divided patients into CPAP+ (those treated with CPAP for at least 6 months) and CPAP- (no ongoing CPAP treatment). Cardiovascular dysautonomia evaluation The clinical evaluation included the presence or absence of cardio-vascular dysautonomia symptoms: palpitations, vertigo, alternating diarrhea-constipation and erectile dysfunction. The heart rate variability (HRV) : we explored the frequency domain and performed a short-term measurement using a Polar H10 heart rate sensor with chest strap (Polar Electro Oy, Professorintie 5, FI-90440 Kempele, Finland) connected via Bluetooth to the Elite HRV application pre-installed on a smartphone, and which allowed exportation of data to the Kubios HRV Standard 3.5.0 software. The pre-humidified sensor was placed around the patient’s chest and recorded heart rate over a period of 10 minutes, after a 2-minute adaptation period. The RR interval was saved in the Elite HRV application, then exported to Kubios HRV software for analysis. The latter studied the RR interval variation and cardiac oscillations. The power of the signal was then calculated for the low frequency (LF, 0.04–0.15 Hz) and the high frequency (HF, 0.15–0.4 Hz) bands expressed in milliseconds squared (ms 2 ), as well as the LF/HF ratio ( 36 ). The normal ranges and modifications ( 37 ) are presented in Table 1 . Functional tests : We realized 3 functional tests to assess the ANS, which are interpreted in Table 2 ( 38 ). Orthostatic hypotension was assessed using an electronic sphygmomanometer (Omron healthcare, Hoofddorp, Neetherlands), cuff at heart level, tubing facing upwards. We performed 2 measures of blood pressure on the right arm of a patient at rest: first after at least 5 minutes in the supine position, then after 2 minutes upright. Orthostatic hypotension was defined as a postural drop in systolic blood pressure > 20mmHg. The Stand test was realized using the H10 HR sensor (described above): after 5 minutes in supine position, the patient moved quickly to standing position in the space of 3 seconds, limiting as much as possible any movement likely to increase the intra-abdominal pressure, in order to attribute the variations in the heart rate only to orthostatism. Normally, during this maneuver, there is an increase in heart rate (maximal towards the 15th second), followed by a bradycardia (maximal around the 30th second). The 30/15 ratio was then defined as the ratio between the longest and the shortest RR interval. For the Controlled ventilation or Deep breathing test, the HR of the patient was continuously measured during 6 consecutive cycles of deep breathing (5-second inspiration and 5-second exhalation) carried out for one minute. The difference between maximum and minimum heart rate during each cycle was noted, and then the average of the 6 differences was calculated. Table 1 Short-term norms for the heart rate variability measures and interpretation of their modifications ( 37 ) Variable Unit Normal values Modification Interpretation Low frequency (LF) ms 2 193–1009 < 193 Impaired SNS High frequency (HF) ms 2 83–3630 < 83 Impaired PNS LF/HF / 1.1–11.6 11.6 Impaired sympatho-vagal equilibrum SNS : sympathetic nervous system, PNS : parasympathetic nervous system Table 2 Measures and impairment of the functional tests exploring cardiovascular dysautonomia Variable Measure Normal Modification Interpretation Orthostatic hypotension Postural drop in SBP ≤ 20 mmHg > 20mmHg Impaired SNS Stand test 30/15 RR interval ≥ 1.04 < 1.04 Impaired PNS Deep breathing Average (max – min) HR in 6 deep breathes ≥ 15 bpm < 15bpm Impaired PNS SBP : systolic blood pressure, SNS : sympathetic nervous system, PNS : parasympathetic nervous system Data analysis The data were entered using the Epidata Entry Database Manager (version 4.4.2.1 Epidata Association, Odense, Denmark, http://www.epidata.dk),exporte d as a csv file, and then imported into R (Foundation for Statistical Computing, Vienna, Austria, https://www.R-project.org/ ) for analysis. At baseline: qualitative data were summarized using proportions, and quantitative data were grouped using the median (25th ,75th percentile). CPAP + and CPAP- groups were compared using Chi square with Yates correction or Fisher exact test for proportions, and Wilcoxon test for quantitative variables; since those groups were of small size. The prevalence of each CV dysautonomia pattern was estimated with its 95% confident interval (95% CI). The association between CPAP therapy and CVD was assessed using Chi square with Yates correction, Fisher, or Wilcoxon tests, according to CVD variable type. The p-value threshold for significant association in this analysis was set at < 0.05. Ethics statement The study was authorized by the head of PMC and approved by the Ethics Committee of the Faculty of Medicine and Biomedical Sciences (University of Yaoundé I). Informed consent to participate was obtained from all of the participants in the study. Our study adhered to the declaration of Helsinki, concerning research conducted on humans and/or human data or material. Results Study population and baseline data Of the 27 patients invited to participate, 19 were included in the analysis (Fig. 1 ). Their age ranged from 43 to 80 years, with a median (1st, 3rd quartiles) of 59 (52.5, 64.0). There were 11 men (57.9%). More than half of the patients had at least one cardiovascular disease; 22.2% were diabetic, and 84.2% were obese. The median apnea-hypopnea index (AHI) was 31/h. Apart from the median neck circumference, which was greater in CPAP+ (120 vs 114, p = 0.038), there was no significant difference between the two treatment groups regarding baseline data (Table 3 ). Table 3 Baseline data of the patients enrolled in the CPAP and cardiovascular dysautonomia study, Yaoundé 2021–2022. Variables* Global (N = 19) CPAP- (N = 11) CPAP+ (N = 8) P-Value Age (years) 59.0 (52.5, 60.0) 59.0 (53.0, 64.0) 55.5 (52.6, 60.7) 0.456 Gender, male 11 (57.8) 5 (45.5) 6 (75.0) 0.352 Alcohol 3 (15.8) 0 (0.0) 3 (37.5) 0.058 Light and screen in bed 14 (73.7) 9 (81.8) 5 (52.5) 0.667 Cardiovascular comorbidity 11 (57.9) 8 (72.7) 3 (37.5) 0.270 Diabetes (N = 18) 4 (22.2) 3 (30.0) 1 (12.5) 0.588 Diurnal symptoms 17 (89.5) 10 (90.9) 7 (87.5) 0.713 Day symptoms (number) 4.0 (1.0, 5.0) 4.0 (3.5, 5.0) 2.0 (1.0, 4.2) 0.293 Night symptoms (number) 6.0 (3.5, 7.5) 6.0 (3.5, 7.5) 6.0 (3.5, 6.5) 0.835 Systolic blood pressure 126.0 (120.5, 134.5) 128.0 (122.5, 134.5) 129.0 (120.8, 134.5) 0.934 Diastolic blood pressure 83.0 (72.5, 87.0) 79.0 (72.5, 87.0) 84.0 (72.2, 86.2) 0.967 Body mass index (Kg/m 2 ) 35.5 (31.8, 42.5) 37.0 (34.3, 45.2) 35.5 (30.0, 38.9) 0.563 Obesity 16 (84.2) 8 (72.7) 8 (100.0) 0.331 Neck circumference 41.0 (37.0, 43.5) 40.0 (36.0, 41.5) 43.5 (41.7, 46.0) 0.038 Waist circumference 118.0 (110.5, 127.5) 114.0 (104.0, 116.3) 120.0 (118.0, 122.8) 0.301 Apnea hypopnea index (/h) 31.0 (15.5, 71.0) 24.0 (15.0, 43.5) 71.0 (22.5, 80.7) 0.148 *Categorical data are expressed as counts (%) and continuous data as median (1st, 3rd quartiles). Table 4 Heart rate variability and functional test results according to CPAP therapy status, CPAP and cardiovascular dysautonomia study, Yaoundé 2021–2022. Variables* Global (N = 19) CPAP- (N = 11) CPAP+ (N = 8) P-Value Low frequency (LF) , ms 2 160.4 (17.7, 924.7) 27.0 (11.5, 535.8) 924.7 (235.0, 1998.9) 0.033 High frequency (HF) , ms 2 111.2 (7.5, 1660.2) 11.4 (6.2, 185.1) 1418.9 (419.1, 3200.6) 0.041 LF/HF 1.1 (0.8, 1.6) 1.3 (1.0, 2.1) 0.8 (0.6, 1.1) 0.076 Orthostatic hypotension 1 (5.3) 0 (0.0) 1 (12.5) 0.179 Stand test (30/15 RR interval) , ms 1.0 (0.9, 1.0) 1.0 (1.0, 1.0) 1.0 (0.9, 1.0) 0.710 Deep breathing (Average (max – min) HR) , /min 3.5 (2.2, 6.1) 2.5 (1.2, 3.6) 6.7 (5.1, 10.4) 0.006 * Categorical data are expressed as counts (%) and continuous data as median (1st, 3rd quartiles) Table 5 Cardiovascular dysautonomia features according to CPAP therapy status, CPAP and cardiovascular dysautonomia study, Yaoundé 2021–2022. Variables Global (N = 19) CPAP- (N = 11) CPAP+ (N = 8) P-Value Sympathetic nervous system Decreased low frequency (LF) 10 (52.6) 8 (72.7) 2 (25.0) 0.036 Orthostatic hypotension 1 (5.3) 0 (0.0) 1 (12.5) 0.179 Global SNS dysautonomia 11 (57.9) 8 (72.7) 3 (37.5) 0.122 Parasympathetic nervous system Decreased high frequency (HF) 8 (42.1) 7 (63.6) 1 (12.5) 0.058 Abnormal stand test 16 (84.2) 11 (100.0) 5 (62.5) 0.058 Abnormal deep breathing 17 (89.5) 11 (100.0) 6 (75.0) 0.164 Global PNS dysautonomia 18 (94.7) 11 (100.0) 7 (87.5) 0.421 SNS – PNS imbalance Decreased LF/HF 11 (57.9) 5 (45.5) 6 (75.0) 0.245 Data are expressed as counts (%) Dysautonomia exploration and CPAP therapy The median LF and HF areas were significantly higher in the CPAP + group, but there was no significant difference for the LF/HF ratio. The frequency of orthostatic hypotension was low (12.5%) and this occurred only in CPAP+. Results for the stand test were similar among both groups, while the average heart rate gap during deep breathing was significantly higher in CPAP+. These data are detailed in Table IV. Identified cardiovascular dysautonomia and CPAP therapy Globally, all the patients included in our study had cardiovascular PNS dysautonomia and only 57.9% of them had at least one feature of SNS dysautonomia. Thus, the frequency of cardiovascular dysautonomia in our sample was 100.0%, and no significant difference was found globally between both groups. Regarding specific features, only decreased LF was significantly associated with the absence of CPAP treatment (Table V). Discussion In this pioneer study of the association between CPAP and cardiovascular dysautonomia in a sub-Saharan African country, the patients were middle-aged adults, predominantly males, with a high representation of obesity, cardiovascular comorbidity, and diabetes. The two treatment groups were similar, apart from a higher cervical perimeter in the CPAP + group. Significant differences were observed in test results but not in the modalities of cardiovascular dysautonomia per se, except for the low-frequency anomaly. The characteristics of our population are in line with those of most clinical studies on OSAHS, particularly in patients treated with CPAP ( 31 , 32 , 40 , 41 , 43 , 45 ), with a mean or median age between 50 and 60 years and an almost constant male predominance, except in the Tasali study, which focused exclusively on women with polycystic ovary syndrome in Chicago ( 40 ), and a moderate to severe OSAS. CPAP + patients had a higher incidence of obesity, as well as higher waist circumference, neck circumference, and AHI; this may reflect a more severe OSAHS, justifying CPAP. CPAP is known to improve OSA symptoms, this could partially explain the higher frequency of symptomatic patients in the CPAP- group. However, we have no hypothesis to explain the greater frequency of cardiovascular comorbidity and diabetes in the CPAP- patients. Even though the group sizes were too small to build any conclusion. The beneficial effect of CPAP on the reduction of ANS disorders has been demonstrated by prospective cohorts and clinical trials, which have mainly focused on HRV ( 30 – 33 , 39 – 45 ). Among these, four ( 41 , 43 – 45 ) used the same HRV indices (LF, HF, LF/HF) as we did. The 3 indices were modified in the CPAP group in all 4 studies, but not significantly. The LF was significantly modified (p ˂ 0.01) only in Roche’s study, which evaluated the effect of 3 months of CPAP in a cohort of 14 patients ( 45 ). HF was significantly increased after CPAP at 1 month and 1 year (p ˂ 0.01) in Ferland's clinical trial, which compared HRV evolution in 20 patients on sibutramine and 18 on CPAP ( 44 ). However, the CPAP+/CPAP- difference in median LF was much greater in our study compared to Roche's study (924.7–27.0 ms 2 vs 7.12–6.12 ms 2 Hz − 1 respectively), and that difference was also greater for HF compared to Ferland's study (1418.9–14.4 ms 2 vs 4.58–4.20 ln ms 2 respectively). As for the LF/HF ratio, our result was close to those of Seaborn et al . ( 43 ) and Ferland et al. ( 44 ), who found no significant change. We didn't find any relevant hypotheses to explain these discrepancies in such small samples which are likely to cause wide sampling fluctuations. However, the presence of such large and statistically significant differences in the two HRV indices despite this small sample size is in favor of a real favorable effect of CPAP on HRV, which is maintained during wakefulness after prolonged use. The deep breathing test is a much more common functional test used to evaluate cardiovascular dysautonomia. However, studies on its association with OSA are scarce. In 2007, Peltier et al. found a non-significant correlation between AHI and functional tests, including deep breathing and tilt tests ( 18 ). More recently, Onanga et al. showed that deep breathing could detect OSA with 100% sensitivity and 86% specificity ( 46 ). We found no study that assessed the association between functional tests and CPAP treatment, but our findings suggest a positive effect of CPAP on cardiac response to deep breathing: although almost all patients had an abnormal HR difference, the average difference was significantly higher in CPAP + patients, who had a more severe OSAS at baseline. Orthostatic hypotension has been rarely described in OSA studies. We found only one study that showed a positive correlation (R = 0.58, p = 0.007) between AHI and mean tilt table blood pressure decrease ( 47 ). Unsurprisingly, abnormal orthostatic hypotension was uncommon in our study since it is often associated with various conditions which do not include OSAS ( 38 ). These facts advocate the need for further research to evaluate functional tests in OSA or CPAP treatment. The main limitation of our study was the small sample size, which made it difficult to identify significant differences between groups, thus reducing the power of the study. This small sample size reflects the fact that OSA is still an emerging pathology in SSA in general and Cameroon in particular. However, even studies carried out in Western or Eastern countries on the association between CPAP and cardiovascular dysautonomia had relatively small numbers, varying between 10 and 55 for 11 of them, including one-third with numbers less than or equal to ours ( 30 – 33 , 39 – 45 ). The monocentric nature of the study also contributed to its small sample size. Lack of human, material, and financial resources prevented us from recruiting on a larger scale or conducting a prospective study that would have established a causal relationship between the treatment and the effects observed. Our interest in the subject prompted us to carry it out as a pilot and exploratory study. Despite these methodological limitations, this work has the merit of having addressed an insufficiently explored area in the evaluation of CPAP efficacy. The demonstration of a potential positive effect of CPAP could be an additional argument for screening for OSA by cardiologists and for compliance with this treatment in OSA patients, particularly those with cardiovascular comorbidity. We deliberately included only patients with OSAHS, without a control group, in the knowledge that the association between this pathology and cardiovascular dysautonomia had already been established ( 14 – 24 ). Conclusion In this small-sample pilot study, at least one feature of cardiovascular dysautonomia was present in all patients with OSA. SNS dysautonomia features were much less frequent than PNS ones. The CPAP + patients presented significantly greater LF and HF powers on HRV evaluation and a higher average heart rate difference on deep breathing test. Regarding single features, only decreased LF was significantly lower in CPAP + compared to CPAP-. Declarations Declarations Ethics approval and consent to participate : • The Ethical board of Faculty of Medicine and Biomedical Sciences approved the study. Each patient involved in the study gave his consent to participated prior to his enrollment. Our study adhered to the declaration of Helsinki, concerning research conducted on humans and/or human data or material. Competing interests : • The authors declare no conflict of interest. Funding : This research did not receive any specific funding. It was performed as part of the employment of the authors in the Faculty of Medicine and Biomedical Sciences. Author Contribution EWPY conceived and designed the study. CBN proceeded to data collection. MM and CBN managed and analysed data. 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Sleep Med Rev. 2014;18(1):19‑24. Milleron O, Pillière R, Foucher A, de Roquefeuil F, Aegerter P, Jondeau G, et al. Benefits of obstructive sleep apnoea treatment in coronary artery disease: a long-term follow-up study. Eur Heart J. 2004;25(9):728‑34. Batool-Anwar S, Goodwin JL, Kushida CA, Walsh JA, Simon RD, Nichols DA, et al. Impact of continuous positive airway pressure (CPAP) on quality of life in patients with obstructive sleep apnea (OSA). Journal of Sleep Research. 2016;25(6):731‑8. Khoo MC, Belozeroff V, Berry RB, Sassoon CS. Cardiac autonomic control in obstructive sleep apnea: effects of long-term CPAP therapy. Am J Respir Crit Care Med. 2001;164(5):807‑12. Efazati N, Rahimi B, Mirdamadi M, Edalatifard M, Tavoosi A. Changes in heart rate variability (HRV) in patients with severe and moderate obstructive sleep apnea before and after acute CPAP therapy during nocturnal polysomnography. Sleep Sci. 2020;13(2):97‑102. Kufoy E, Palma JA, Lopez J, Alegre M, Urrestarazu E, Artieda J, et al. Changes in the heart rate variability in patients with obstructive sleep apnea and its response to acute CPAP treatment. PLoS One. 2012;7(3):e33769. Nastałek P, Bochenek G, Kania A, Celejewska-Wójcik N, Mejza F, Sładek K. Heart Rate Variability in the Diagnostics and CPAP Treatment of Obstructive Sleep Apnea. Adv Exp Med Biol. 2019;1176:25‑33. Correia FJ, Martins LEB, Barreto DM, Pithon KR. Repercussion of medium and long treatment period with continuous positive airways pressure therapy in heart rate variability of obstructive sleep apnea. Sleep Sci. 2019;12(2):110‑5. Guo W, Lv T, She F, Miao G, Liu Y, He R, et al. The impact of continuous positive airway pressure on heart rate variability in obstructive sleep apnea patients during sleep: A meta-analysis. Heart Lung. 2018;47(5):516‑24. Shaffer F, Ginsberg JP. An Overview of Heart Rate Variability Metrics and Norms. Front Public Health. 2017;5:258. Nunan D, Sandercock GRH, Brodie DA. A Quantitative Systematic Review of Normal Values for Short-Term Heart Rate Variability in Healthy Adults. Pacing and Clinical Electrophysiology 2010;33(11):1407‑17. Jones PK, Shaw B, Raj SR. Orthostatic hypotension: managing a difficult problem. Expert Rev Cardiovasc Ther. 2015;13(11):1263‑76. Dal-Fabbro C, Garbuio S, D’Almeida V, Cintra FD, Tufik S, Bittencourt L. Mandibular advancement device and CPAP upon cardiovascular parameters in OSA. Sleep Breath. 2014;18(4):749‑59. Tasali E, Chapotot F, Leproult R, Whitmore H, Ehrmann DA. Treatment of Obstructive Sleep Apnea Improves Cardiometabolic Function in Young Obese Women with Polycystic Ovary Syndrome. The Journal of Clinical Endocrinology & Metabolism. 2011;96(2):365‑74. Shiina K, Tomiyama H, Takata Y, Yoshida M, Kato K, Saruhara H, et al. Effects of CPAP therapy on the sympathovagal balance and arterial stiffness in obstructive sleep apnea. Respiratory Medicine. 2010;104(6):911‑6. Limphanudom P, Chierakul N, Pinyopattarakul N, Nana A, Naruman C, Tangchityongsiva S, et al. Recovery of heart rate variability in patients with moderate to severe obstructive sleep apnea after 6-month continuous positive airway pressure treatment. J Med Assoc Thai. 2007;90(8):1530‑5. Seaborn GE, Pang H, Akl SG, Redfearn DP. Autonomic profile of patients referred to a sleep disorder clinic: impact of CPAP on the autonomic nervous system. Rev Urug Cardiol. 2012;27:143-7 Ferland A, Poirier P, Sériès F. Sibutramine versus continuous positive airway pressure in obese obstructive sleep apnoea patients. European Respiratory Journal. 2009;34(3):694‑701. Roche F, Court-Fortune I, Pichot V, Duverney D, Costes F, Emonot A, et al. Reduced cardiac sympathetic autonomic tone after long-term nasal continuous positive airway pressure in obstructive sleep apnoea syndrome. Clin Physiol. 1999;19(2):127‑34. Onanga M, Joanny S, Rivals I, Perger E, Arnulf I, Redolfi S, et al. Screening of obstructive sleep apnea syndrome by the deep breathing technique. J Clin Sleep Med. 2023;19(2):293-302. Woodson BT, Brusky LT, Saurajen A, Jaradeh S. Association of Autonomic Dysfunction and Mild Obstructive Sleep Apnea. Otolaryngol Head Neck Surg. 2004;130(6):643‑8. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviewers invited by journal 30 Sep, 2025 Editor assigned by journal 22 Sep, 2025 Editor invited by journal 03 Sep, 2025 Submission checks completed at journal 02 Sep, 2025 First submitted to journal 02 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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1","display":"","copyAsset":false,"role":"figure","size":20079,"visible":true,"origin":"","legend":"\u003cp\u003eFlow chart for patient inclusion in the study on Continuous positive airways pressure therapy and cardiovascular dysautonomia among obstructive sleep apnea patients in Yaoundé, 2020 - 2021.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6863517/v1/f6db3b7be94a89886f681d2f.png"},{"id":93543551,"identity":"f0ec4873-0cc2-4d71-9bf9-63b5e1c4bf56","added_by":"auto","created_at":"2025-10-15 02:43:25","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1181249,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6863517/v1/3ff5cf34-2898-49d9-9106-ee2c31f76b21.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Continuous positive airways pressure therapy and cardiovascular dysautonomia among obstructive sleep apnea patients in Yaoundé, Cameroon: a pilot study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eObstructive sleep apnea (OSA) is a major public health issue characterized by repetitive episodes of partial or total occlusion of the upper airway during sleep, causing exaggerated effort to breathe against the occluded airway, sleep fragmentation, and intermittent hypoxemia. Clinically relevant obstructive sleep apnea hypopnea syndrome (OSAHS) has a prevalence of 3 to 7% for men and 1 to 4% for women in the general population (\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e), and up to 49.6% in a Cameroonian hospitalized-patients sample (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). The prevalence of sleep-disordered breathing (SDB), not taking into account the clinical manifestations, is much higher both in community-based studies (40\u0026ndash;80% in developed countries, 36% in Cameroon) and hospital-based ones (57.7% in Central Hospital of Yaound\u0026eacute;, Cameroon) (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). The effects of OSA during sleep (especially intermittent hypoxia) elicit a number of intermediate mechanisms, including sympathetic activation, endothelial dysfunction, oxidative stress, inflammation, and metabolic dysfunction, which can contribute to increased cardiovascular risk. This has been confirmed by several studies demonstrating the association of OSAHS with a poor cardiovascular outcome (\u003cspan additionalcitationids=\"CR9 CR10 CR11 CR12\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). These cardiovascular disorders can, at least partially, involve a cardiovascular-related autonomic nervous system (ANS) impairment, or cardiovascular dysautonomia (CVD). During obstructive events, hypoxemia and hypercapnia episodes can increase sympathetic tonus and responsiveness, which can contribute to sympatho-vagal imbalance and, in consequence, dysautonomia. The association between OSA and CVD has been widely described in the literature, especially in the past decade (\u003cspan additionalcitationids=\"CR15 CR16 CR17 CR18 CR19 CR20 CR21 CR22 CR23\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e). A few authors have even suggested some features of CVD as tools for OSA screening (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e). Continuous positive airway pressure (CPAP) is the most efficacious and commonly used treatment for patients with OSA. CPAP treatment has been shown to improve OSA-related symptoms, reduce blood pressure, ameliorate cardiovascular risk, and improve quality of life in severe patients (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan additionalcitationids=\"CR28\" citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eWe found a few studies (\u003cspan additionalcitationids=\"CR31 CR32\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e) and two reviews (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e) that sought the impact of CPAP on CVD. Their results suggest a positive effect of CPAP. However, none were carried out in Africa. The aim of our study was to search for the association between CPAP therapy and CVD among OSA patients in Cameroon, where OSAHS is still an emerging disease.\u003c/p\u003e"},{"header":"Methodology","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStudy design and setting\u003c/h2\u003e\u003cp\u003eThis was a hospital-based cross-sectional study from December 2020 to May 2021 at the Polymer Medical Center (PMC) in Yaounde. PMC is a major center for respiratory diseases, including sleep disordered breathing (SDB) and especially OSA, which are an emerging condition in Sub-Saharan Africa (SSA), with limited access to diagnosis, and moreover CPAP therapy. The center receives patients from Yaounde and other regions of Cameroon. A sleep laboratory is present, having both polygraphy and polysomnography.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eStudy population and sampling\u003c/h3\u003e\n\u003cp\u003ePMC patients aged at least 30 years old, and who had been diagnosed with OSA at least 6 months ago were invited to participate. Those presenting with motor, behavioral or consciousness disorders were excluded from the sample. We used the sleep laboratory register to identify eligible patients. The eligible ones were invited by phone call or physically as they attended PMC for their follow-up, according to their treatment status.\u003c/p\u003e\n\u003ch3\u003eData collection\u003c/h3\u003e\n\u003cp\u003eData were collected by a 7th year trained medical student both from the patient\u0026rsquo;s file and during a face-to-face interview during which physical examination and assessment for cardiovascular dysautonomia were done. These were recorded on a pre-prepared data collection form.\u003c/p\u003e\n\u003ch3\u003eBaseline data\u003c/h3\u003e\n\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eDemographic and habitus\u003c/b\u003e: age and sex were recorded as numeric and dichotomic variables respectively. Smoking status was categorized into non-smoker (person not actively smoking and who has smoked\u0026thinsp;\u0026lt;\u0026thinsp;20 packets of cigarettes during their whole life), smoker (person actively smoking), and ex-smoker (person who has smoked 20 packets or more and has stopped smoking for at least 6 months). Alcohol consumption was divided into consumer and non-consumer (no alcohol consumption in the last 3 months). Drug intake was divided into presence (person taking at least one drug for a chronic condition) and absence (no long-term drug).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eComorbid conditions\u003c/b\u003e: the presence of cardiovascular comorbidity or risk factor (hypertension, diabetes mellitus, stroke, heart failure) was recorded as a dichotomic variable (presence or absence).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eClinical features\u003c/b\u003e: weight was measured using a digital wireless scale, and height was measured using a graduated stadiometer. Both allowed the calculation of the body mass index (weight in kg/ height\u003csup\u003e2\u003c/sup\u003e in m\u003csup\u003e2\u003c/sup\u003e). The latter was then used to define the following weight categories: underweight (\u0026lt;\u0026thinsp;18.5 kg/m\u003csup\u003e2\u003c/sup\u003e), normal (18.5\u0026ndash;24.9 kg/m\u003csup\u003e2\u003c/sup\u003e), overweight (25-29.9 kg/m\u003csup\u003e2\u003c/sup\u003e) and obesity (\u0026ge;\u0026thinsp;30 kg/m\u003csup\u003e2\u003c/sup\u003e).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eOSA and CPAP-related data\u003c/b\u003e: The apnea-hypopnea index (AHI) was recorded as numeric variable. It was subsequently used to define OSA severity groups as mild (\u0026lt;\u0026thinsp;15/h), moderate (15\u0026ndash;29/h) and severe (\u0026ge;\u0026thinsp;30/h). CPAP therapy status divided patients into CPAP+ (those treated with CPAP for at least 6 months) and CPAP- (no ongoing CPAP treatment).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\n\u003ch3\u003eCardiovascular dysautonomia evaluation\u003c/h3\u003e\n\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eThe clinical evaluation\u003c/b\u003e included the presence or absence of cardio-vascular dysautonomia symptoms: palpitations, vertigo, alternating diarrhea-constipation and erectile dysfunction.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eThe heart rate variability (HRV)\u003c/b\u003e: we explored the frequency domain and performed a short-term measurement using a Polar H10 heart rate sensor with chest strap (Polar Electro Oy, Professorintie 5, FI-90440 Kempele, Finland) connected via Bluetooth to the Elite HRV application pre-installed on a smartphone, and which allowed exportation of data to the Kubios HRV Standard 3.5.0 software. The pre-humidified sensor was placed around the patient\u0026rsquo;s chest and recorded heart rate over a period of 10 minutes, after a 2-minute adaptation period. The RR interval was saved in the Elite HRV application, then exported to Kubios HRV software for analysis. The latter studied the RR interval variation and cardiac oscillations. The power of the signal was then calculated for the low frequency (LF, 0.04\u0026ndash;0.15 Hz) and the high frequency (HF, 0.15\u0026ndash;0.4 Hz) bands expressed in milliseconds squared (ms\u003csup\u003e2\u003c/sup\u003e), as well as the LF/HF ratio (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e). The normal ranges and modifications (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e) are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eFunctional tests\u003c/b\u003e: We realized 3 functional tests to assess the ANS, which are interpreted in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e). Orthostatic hypotension was assessed using an electronic sphygmomanometer (Omron healthcare, Hoofddorp, Neetherlands), cuff at heart level, tubing facing upwards. We performed 2 measures of blood pressure on the right arm of a patient at rest: first after at least 5 minutes in the supine position, then after 2 minutes upright. Orthostatic hypotension was defined as a postural drop in systolic blood pressure\u0026thinsp;\u0026gt;\u0026thinsp;20mmHg. The Stand test was realized using the H10 HR sensor (described above): after 5 minutes in supine position, the patient moved quickly to standing position in the space of 3 seconds, limiting as much as possible any movement likely to increase the intra-abdominal pressure, in order to attribute the variations in the heart rate only to orthostatism. Normally, during this maneuver, there is an increase in heart rate (maximal towards the 15th second), followed by a bradycardia (maximal around the 30th second). The 30/15 ratio was then defined as the ratio between the longest and the shortest RR interval. For the Controlled ventilation or Deep breathing test, the HR of the patient was continuously measured during 6 consecutive cycles of deep breathing (5-second inspiration and 5-second exhalation) carried out for one minute. The difference between maximum and minimum heart rate during each cycle was noted, and then the average of the 6 differences was calculated.\u003c/p\u003e\u003c/li\u003e\u003c/ul\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\u003eShort-term norms for the heart rate variability measures and interpretation of their modifications (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eUnit\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNormal values\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eModification\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eInterpretation\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLow frequency (LF)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ems\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e193\u0026ndash;1009\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;193\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eImpaired SNS\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHigh frequency (HF)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ems\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e83\u0026ndash;3630\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eImpaired PNS\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLF/HF\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e/\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.1\u0026ndash;11.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;1.11 or \u0026gt;\u0026thinsp;11.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eImpaired sympatho-vagal equilibrum\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e\u003cp\u003e\u003cem\u003eSNS : sympathetic nervous system, PNS : parasympathetic nervous system\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\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\u003eMeasures and impairment of the functional tests exploring cardiovascular dysautonomia\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMeasure\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNormal\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eModification\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eInterpretation\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOrthostatic hypotension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePostural drop in SBP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026le;\u0026thinsp;20 mmHg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026gt;\u0026thinsp;20mmHg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eImpaired SNS\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eStand test\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30/15 RR interval\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026ge;\u0026thinsp;1.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;1.04\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eImpaired PNS\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDeep breathing\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAverage (max \u0026ndash; min) HR in 6 deep breathes\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026ge;\u0026thinsp;15 bpm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;15bpm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eImpaired PNS\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e\u003cp\u003e\u003cem\u003eSBP\u0026nbsp;: systolic blood pressure, SNS : sympathetic nervous system, PNS : parasympathetic nervous system\u003c/em\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eData analysis\u003c/h2\u003e\u003cp\u003eThe data were entered using the Epidata Entry Database Manager (version 4.4.2.1 Epidata Association, Odense, Denmark, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.epidata.dk),exporte\u003c/span\u003e\u003cspan address=\"http://www.epidata.dk),exporte\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003ed\u003c/span\u003e as a csv file, and then imported into R (Foundation for Statistical Computing, Vienna, Austria, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.R-project.org/\u003c/span\u003e\u003cspan address=\"https://www.R-project.org/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e) for analysis.\u003c/p\u003e\u003cp\u003eAt baseline: qualitative data were summarized using proportions, and quantitative data were grouped using the median (25th ,75th percentile). CPAP\u0026thinsp;+\u0026thinsp;and CPAP- groups were compared using Chi square with Yates correction or Fisher exact test for proportions, and Wilcoxon test for quantitative variables; since those groups were of small size.\u003c/p\u003e\u003cp\u003eThe prevalence of each CV dysautonomia pattern was estimated with its 95% confident interval (95% CI). The association between CPAP therapy and CVD was assessed using Chi square with Yates correction, Fisher, or Wilcoxon tests, according to CVD variable type. The p-value threshold for significant association in this analysis was set at \u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eEthics statement\u003c/h3\u003e\n\u003cp\u003e The study was authorized by the head of PMC and approved by the Ethics Committee of the Faculty of Medicine and Biomedical Sciences (University of Yaound\u0026eacute; I). Informed consent to participate was obtained from all of the participants in the study. Our study adhered to the declaration of Helsinki, concerning research conducted on humans and/or human data or material.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eStudy population and baseline data\u003c/h2\u003e\u003cp\u003eOf the 27 patients invited to participate, 19 were included in the analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Their age ranged from 43 to 80 years, with a median (1st, 3rd quartiles) of 59 (52.5, 64.0). There were 11 men (57.9%). More than half of the patients had at least one cardiovascular disease; 22.2% were diabetic, and 84.2% were obese. The median apnea-hypopnea index (AHI) was 31/h. Apart from the median neck circumference, which was greater in CPAP+ (120 vs 114, p\u0026thinsp;=\u0026thinsp;0.038), there was no significant difference between the two treatment groups regarding baseline data (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\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\u003eBaseline data of the patients enrolled in the CPAP and cardiovascular dysautonomia study, Yaound\u0026eacute; 2021\u0026ndash;2022.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariables*\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGlobal (N\u0026thinsp;=\u0026thinsp;19)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCPAP- (N\u0026thinsp;=\u0026thinsp;11)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCPAP+ (N\u0026thinsp;=\u0026thinsp;8)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\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\u003e\u003cb\u003eAge (years)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e59.0 (52.5, 60.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e59.0 (53.0, 64.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e55.5 (52.6, 60.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.456\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eGender, male\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e11 (57.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5 (45.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6 (75.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.352\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eAlcohol\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3 (15.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 (0.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3 (37.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.058\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eLight and screen in bed\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e14 (73.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9 (81.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5 (52.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.667\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCardiovascular comorbidity\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e11 (57.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8 (72.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3 (37.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.270\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eDiabetes (N\u0026thinsp;=\u0026thinsp;18)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4 (22.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3 (30.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1 (12.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.588\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eDiurnal symptoms\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e17 (89.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10 (90.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7 (87.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.713\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eDay symptoms (number)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e4.0 (1.0, 5.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.0 (3.5, 5.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.0 (1.0, 4.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.293\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eNight symptoms (number)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e6.0 (3.5, 7.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e6.0 (3.5, 7.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.0 (3.5, 6.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.835\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eSystolic blood pressure\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e126.0 (120.5, 134.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e128.0 (122.5, 134.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e129.0 (120.8, 134.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.934\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eDiastolic blood pressure\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e83.0 (72.5, 87.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e79.0 (72.5, 87.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e84.0 (72.2, 86.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.967\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eBody mass index\u003c/b\u003e (Kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e35.5 (31.8, 42.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e37.0 (34.3, 45.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e35.5 (30.0, 38.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.563\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eObesity\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e16 (84.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8 (72.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e8 (100.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.331\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eNeck circumference\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e41.0 (37.0, 43.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e40.0 (36.0, 41.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e43.5 (41.7, 46.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003e0.038\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eWaist circumference\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e118.0 (110.5, 127.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e114.0 (104.0, 116.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e120.0 (118.0, 122.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.301\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eApnea hypopnea index (/h)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e31.0 (15.5, 71.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e24.0 (15.0, 43.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e71.0 (22.5, 80.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.148\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u003cem\u003e*Categorical data are expressed as counts (%) and continuous data as median (1st, 3rd quartiles).\u003c/em\u003e\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=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eHeart rate variability and functional test results according to CPAP therapy status, CPAP and cardiovascular dysautonomia study, Yaound\u0026eacute; 2021\u0026ndash;2022.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariables*\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGlobal (N\u0026thinsp;=\u0026thinsp;19)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCPAP- (N\u0026thinsp;=\u0026thinsp;11)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCPAP+ (N\u0026thinsp;=\u0026thinsp;8)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\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\u003e\u003cb\u003eLow frequency (LF)\u003c/b\u003e, ms\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e160.4 (17.7, 924.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e27.0 (11.5, 535.8)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e924.7 (235.0, 1998.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003e0.033\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eHigh frequency (HF)\u003c/b\u003e, ms\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e111.2 (7.5, 1660.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11.4 (6.2, 185.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1418.9 (419.1, 3200.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003e0.041\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eLF/HF\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.1 (0.8, 1.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.3 (1.0, 2.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.8 (0.6, 1.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.076\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eOrthostatic hypotension\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (5.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 (0.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1 (12.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.179\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eStand test (30/15 RR interval)\u003c/b\u003e, ms\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1.0 (0.9, 1.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1.0 (1.0, 1.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1.0 (0.9, 1.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.710\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eDeep breathing (Average (max \u0026ndash; min) HR)\u003c/b\u003e, /min\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3.5 (2.2, 6.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e2.5 (1.2, 3.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.7 (5.1, 10.4)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003e0.006\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e* \u003cem\u003eCategorical data are expressed as counts (%) and continuous data as median (1st, 3rd quartiles)\u003c/em\u003e\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=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eCardiovascular dysautonomia features according to CPAP therapy status, CPAP and cardiovascular dysautonomia study, Yaound\u0026eacute; 2021\u0026ndash;2022.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariables\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eGlobal (N\u0026thinsp;=\u0026thinsp;19)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eCPAP- (N\u0026thinsp;=\u0026thinsp;11)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCPAP+ (N\u0026thinsp;=\u0026thinsp;8)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eP-Value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e\u003cp\u003eSympathetic nervous system\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDecreased low frequency (LF)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10 (52.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8 (72.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2 (25.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003e0.036\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOrthostatic hypotension\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (5.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 (0.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1 (12.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.179\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGlobal SNS dysautonomia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e11 (57.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e8 (72.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3 (37.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.122\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003eParasympathetic nervous system\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDecreased high frequency (HF)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e8 (42.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7 (63.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e1 (12.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.058\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbnormal stand test\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e16 (84.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11 (100.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5 (62.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.058\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAbnormal deep breathing\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e17 (89.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11 (100.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6 (75.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.164\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGlobal PNS dysautonomia\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e18 (94.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e11 (100.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e7 (87.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.421\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e\u003cp\u003e\u003cb\u003eSNS \u0026ndash; PNS imbalance\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDecreased LF/HF\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e11 (57.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5 (45.5)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6 (75.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.245\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u003cem\u003eData are expressed as counts (%)\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eDysautonomia exploration and CPAP therapy\u003c/h2\u003e\u003cp\u003eThe median LF and HF areas were significantly higher in the CPAP\u0026thinsp;+\u0026thinsp;group, but there was no significant difference for the LF/HF ratio. The frequency of orthostatic hypotension was low (12.5%) and this occurred only in CPAP+. Results for the stand test were similar among both groups, while the average heart rate gap during deep breathing was significantly higher in CPAP+. These data are detailed in Table IV.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003eIdentified cardiovascular dysautonomia and CPAP therapy\u003c/h2\u003e\u003cp\u003eGlobally, all the patients included in our study had cardiovascular PNS dysautonomia and only 57.9% of them had at least one feature of SNS dysautonomia. Thus, the frequency of cardiovascular dysautonomia in our sample was 100.0%, and no significant difference was found globally between both groups. Regarding specific features, only decreased LF was significantly associated with the absence of CPAP treatment (Table V).\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this pioneer study of the association between CPAP and cardiovascular dysautonomia in a sub-Saharan African country, the patients were middle-aged adults, predominantly males, with a high representation of obesity, cardiovascular comorbidity, and diabetes. The two treatment groups were similar, apart from a higher cervical perimeter in the CPAP\u0026thinsp;+\u0026thinsp;group. Significant differences were observed in test results but not in the modalities of cardiovascular dysautonomia per se, except for the low-frequency anomaly.\u003c/p\u003e\u003cp\u003eThe characteristics of our population are in line with those of most clinical studies on OSAHS, particularly in patients treated with CPAP (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e), with a mean or median age between 50 and 60 years and an almost constant male predominance, except in the Tasali study, which focused exclusively on women with polycystic ovary syndrome in Chicago (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e), and a moderate to severe OSAS. CPAP\u0026thinsp;+\u0026thinsp;patients had a higher incidence of obesity, as well as higher waist circumference, neck circumference, and AHI; this may reflect a more severe OSAHS, justifying CPAP. CPAP is known to improve OSA symptoms, this could partially explain the higher frequency of symptomatic patients in the CPAP- group. However, we have no hypothesis to explain the greater frequency of cardiovascular comorbidity and diabetes in the CPAP- patients. Even though the group sizes were too small to build any conclusion.\u003c/p\u003e\u003cp\u003eThe beneficial effect of CPAP on the reduction of ANS disorders has been demonstrated by prospective cohorts and clinical trials, which have mainly focused on HRV (\u003cspan additionalcitationids=\"CR31 CR32\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan additionalcitationids=\"CR40 CR41 CR42 CR43 CR44\" citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e). Among these, four (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan additionalcitationids=\"CR44\" citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e) used the same HRV indices (LF, HF, LF/HF) as we did. The 3 indices were modified in the CPAP group in all 4 studies, but not significantly. The LF was significantly modified (p ˂ 0.01) only in Roche\u0026rsquo;s study, which evaluated the effect of 3 months of CPAP in a cohort of 14 patients (\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e). HF was significantly increased after CPAP at 1 month and 1 year (p ˂ 0.01) in Ferland's clinical trial, which compared HRV evolution in 20 patients on sibutramine and 18 on CPAP (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e). However, the CPAP+/CPAP- difference in median LF was much greater in our study compared to Roche's study (924.7\u0026ndash;27.0 ms\u003csup\u003e2\u003c/sup\u003e vs 7.12\u0026ndash;6.12 ms\u003csup\u003e2\u003c/sup\u003eHz\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e respectively), and that difference was also greater for HF compared to Ferland's study (1418.9\u0026ndash;14.4 ms\u003csup\u003e2\u003c/sup\u003e vs 4.58\u0026ndash;4.20 ln ms\u003csup\u003e2\u003c/sup\u003e respectively). As for the LF/HF ratio, our result was close to those of Seaborn et \u003cem\u003eal\u003c/em\u003e. (\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e) and Ferland et \u003cem\u003eal.\u003c/em\u003e (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e), who found no significant change. We didn't find any relevant hypotheses to explain these discrepancies in such small samples which are likely to cause wide sampling fluctuations. However, the presence of such large and statistically significant differences in the two HRV indices despite this small sample size is in favor of a real favorable effect of CPAP on HRV, which is maintained during wakefulness after prolonged use.\u003c/p\u003e\u003cp\u003eThe deep breathing test is a much more common functional test used to evaluate cardiovascular dysautonomia. However, studies on its association with OSA are scarce. In 2007, Peltier et \u003cem\u003eal.\u003c/em\u003e found a non-significant correlation between AHI and functional tests, including deep breathing and tilt tests (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e). More recently, Onanga et \u003cem\u003eal.\u003c/em\u003e showed that deep breathing could detect OSA with 100% sensitivity and 86% specificity (\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e). We found no study that assessed the association between functional tests and CPAP treatment, but our findings suggest a positive effect of CPAP on cardiac response to deep breathing: although almost all patients had an abnormal HR difference, the average difference was significantly higher in CPAP\u0026thinsp;+\u0026thinsp;patients, who had a more severe OSAS at baseline. Orthostatic hypotension has been rarely described in OSA studies. We found only one study that showed a positive correlation (R\u0026thinsp;=\u0026thinsp;0.58, p\u0026thinsp;=\u0026thinsp;0.007) between AHI and mean tilt table blood pressure decrease (\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e). Unsurprisingly, abnormal orthostatic hypotension was uncommon in our study since it is often associated with various conditions which do not include OSAS (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e). These facts advocate the need for further research to evaluate functional tests in OSA or CPAP treatment.\u003c/p\u003e\u003cp\u003eThe main limitation of our study was the small sample size, which made it difficult to identify significant differences between groups, thus reducing the power of the study. This small sample size reflects the fact that OSA is still an emerging pathology in SSA in general and Cameroon in particular. However, even studies carried out in Western or Eastern countries on the association between CPAP and cardiovascular dysautonomia had relatively small numbers, varying between 10 and 55 for 11 of them, including one-third with numbers less than or equal to ours (\u003cspan additionalcitationids=\"CR31 CR32\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan additionalcitationids=\"CR40 CR41 CR42 CR43 CR44\" citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e). The monocentric nature of the study also contributed to its small sample size. Lack of human, material, and financial resources prevented us from recruiting on a larger scale or conducting a prospective study that would have established a causal relationship between the treatment and the effects observed. Our interest in the subject prompted us to carry it out as a pilot and exploratory study. Despite these methodological limitations, this work has the merit of having addressed an insufficiently explored area in the evaluation of CPAP efficacy. The demonstration of a potential positive effect of CPAP could be an additional argument for screening for OSA by cardiologists and for compliance with this treatment in OSA patients, particularly those with cardiovascular comorbidity. We deliberately included only patients with OSAHS, without a control group, in the knowledge that the association between this pathology and cardiovascular dysautonomia had already been established (\u003cspan additionalcitationids=\"CR15 CR16 CR17 CR18 CR19 CR20 CR21 CR22 CR23\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e).\u003c/p\u003e"},{"header":"Conclusion ","content":"\u003cp\u003eIn this small-sample pilot study, at least one feature of cardiovascular dysautonomia was present in all patients with OSA. SNS dysautonomia features were much less frequent than PNS ones. The CPAP\u0026thinsp;+\u0026thinsp;patients presented significantly greater LF and HF powers on HRV evaluation and a higher average heart rate difference on deep breathing test. Regarding single features, only decreased LF was significantly lower in CPAP\u0026thinsp;+\u0026thinsp;compared to CPAP-.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eDeclarations\u003c/h2\u003e\u003cp\u003e\u003cstrong\u003e\u003cb\u003eEthics approval and consent to participate\u003c/b\u003e :\u003c/strong\u003e\u003cp\u003e \u0026bull; The Ethical board of Faculty of Medicine and Biomedical Sciences approved the study. Each patient involved in the study gave his consent to participated prior to his enrollment. Our study adhered to the declaration of Helsinki, concerning research conducted on humans and/or human data or material.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003e\u003cb\u003eCompeting interests\u003c/b\u003e :\u003c/h2\u003e\u003cp\u003e\u0026bull; The authors declare no conflict of interest.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding :\u003c/h2\u003e\u003cp\u003eThis research did not receive any specific funding. It was performed as part of the employment of the authors in the Faculty of Medicine and Biomedical Sciences.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eEWPY conceived and designed the study. CBN proceeded to data collection. MM and CBN managed and analysed data. MM drafted and edited the manuscript. MM, AON, MENK, AK, AWN and EWPY reviewed the manuscript. All authors have read and aproved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements :\u003c/h2\u003e\u003cp\u003e\u0026bull; None\u003c/p\u003e\u003cp\u003e\u0026bull; \u003cb\u003eClinical trial number\u003c/b\u003e : not applicable.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eData supporting the conclusions of this study can be accessed upon reasonable demand, by email to [email protected]\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003ePunjabi NM. The epidemiology of adult obstructive sleep apnea. 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Otolaryngol Head Neck Surg. 2004;130(6):643‑8. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-cardiovascular-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bcar","sideBox":"Learn more about [BMC Cardiovascular Disorders](http://bmccardiovascdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bcar/default.aspx","title":"BMC Cardiovascular Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"obstructive sleep apnea syndrome, continuous positive airway pressure, cardiovascular dysautonomia","lastPublishedDoi":"10.21203/rs.3.rs-6863517/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6863517/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjective\u003c/h2\u003e\u003cp\u003eWe aimed to study the association between cardiovascular dysautonomia and CPAP in patients with obstructive sleep apnea in Yaound\u0026eacute;, Cameroon.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eFrom December 2020 to May 2021, we enrolled obstructive sleep apnea patients, treated with CPAP (CPAP+) or not (CPAP-). We assessed cardiovascular dysautonomia using functional tests (deep breathing, stand test and orthostatic hypotension) and heart rate variability (HRV). The latter was studied using the Kubios HRV Standard 3.5.0 software, and included low frequency (LF), high frequency (HF) and LF/ HF ratio. We compared qualitative and quantitative variables between the two patient groups with the Fisher exact and Wilcoxon tests respectively. The significance threshold was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 .\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eWe enrolled 8 CPAP\u0026thinsp;+\u0026thinsp;and 11 CPAP-, with median ages (25th, 75th percentiles) 55.5 (52.6, 60.7) and 59 (53.0, 64.0) years respectively. CPAP therapy was associated with LF area (p\u0026thinsp;=\u0026thinsp;0.033), HF area (p\u0026thinsp;=\u0026thinsp;0.041) and heart rate difference on deep breathing test (p\u0026thinsp;=\u0026thinsp;0,006). All patients had at least one feature of cardiovascular dysautonomia. Compared to CPAP+, CPAP- presented a greater proportion of abnormal LF (72.7% vs 25.0%, p\u0026thinsp;=\u0026thinsp;0.069), HF (63.64% vs 12.5%, p\u0026thinsp;=\u0026thinsp;0.058), deep breathing (100.0% vs 75.0%, p\u0026thinsp;=\u0026thinsp;0.163) and stand test (100.0% vs 62.5%, p\u0026thinsp;=\u0026thinsp;0.058), SNS dysautonomia (72.7% vs 37.5%, p\u0026thinsp;=\u0026thinsp;0.122) and PNS dysautonomia (100.0% vs 87.5%, p\u0026thinsp;=\u0026thinsp;0.421).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e\u003cp\u003eIn this small sample size pilot study, CPAP\u0026thinsp;+\u0026thinsp;patients presented greater LF and HF powers, and higher average heart rate difference on deep breathing test. Regarding single features, only decreased LF was lower in CPAP\u0026thinsp;+\u0026thinsp;compared to CPAP-.\u003c/p\u003e","manuscriptTitle":"Continuous positive airways pressure therapy and cardiovascular dysautonomia among obstructive sleep apnea patients in Yaoundé, Cameroon: a pilot study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-15 02:19:16","doi":"10.21203/rs.3.rs-6863517/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewersInvited","content":"","date":"2025-09-30T07:02:32+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-22T17:11:13+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-09-03T05:54:59+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-02T23:48:32+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Cardiovascular Disorders","date":"2025-09-02T23:45:49+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-cardiovascular-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bcar","sideBox":"Learn more about [BMC Cardiovascular Disorders](http://bmccardiovascdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bcar/default.aspx","title":"BMC Cardiovascular Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5d11b8ec-42fe-4cf6-9376-f0a32bba3590","owner":[],"postedDate":"October 15th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-10-15T02:19:16+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-15 02:19:16","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6863517","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6863517","identity":"rs-6863517","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}