Integrated Clinical, Anthropometric, Cardiometabolic, and Autonomic Determinants of Obstructive Sleep Apnea Severity: A Cross-Sectional Study

Abstract

Background: Obstructive sleep apnea (OSA) is a heterogeneous sleep-related breathing disorder associated with obesity, cardiometabolic comorbidities, nocturnal hypoxemia, and cardiovascular autonomic dysfunction. Although these factors are individually associated with OSA severity, their combined clinical and physiological relationships remain incompletely characterized. This study aimed to provide an integrated assessment of the clinical, anthropometric, cardiometabolic, hypoxemic, and autonomic determinants of OSA severity in adults undergoing sleep evaluation. Methods: This hospital-based cross-sectional observational study included 84 adults with OSA who underwent overnight evaluation using a Deck Mount Level III Sleep Apnea Monitoring Device. Demographic and anthropometric characteristics, cardiometabolic comorbidities, respiratory indices, and nocturnal oxygenation parameters were assessed. OSA severity was classified according to the Apnea–Hypopnea Index (AHI) as mild (5–14.9 events/hour), moderate (15–29.9 events/hour), or severe (?30 events/hour). Cardiovascular autonomic function was evaluated using heart rate variability (HRV), Valsalva ratio, deep breathing expiratory-to-inspiratory (E:I) ratio, and orthostatic blood pressure response. Associations and correlations between OSA severity and clinical, hypoxemic, and autonomic parameters were assessed using appropriate statistical methods. Results: Among the 84 participants, 13 (15.5%) had mild, 32 (38.1%) moderate, and 39 (46.4%) severe OSA. The overall mean age was approximately 49 years, with a marked male predominance, and the mean BMI was approximately 31 kg/m². Increasing OSA severity was associated with higher BMI, greater AHI and ODI, and progressively impaired nocturnal oxygenation. Mean AHI increased from 10.2 ± 2.8 events/hour in mild OSA to 22.1 ± 4.5 events/hour in moderate and 46.8 ± 12.7 events/hour in severe OSA (p<0.001), while average and minimum SpO? declined significantly with increasing severity. Cardiometabolic comorbidities, particularly obesity, hypertension, and type 2 diabetes mellitus, were common among patients undergoing sleep evaluation and were associated with more severe OSA in the reported cohort. Autonomic dysfunction progressively worsened with increasing OSA severity. HRV declined from 42.6 ± 8.1 ms in mild OSA to 36.4 ± 7.5 ms in moderate and 29.8 ± 6.9 ms in severe OSA (p<0.001). Valsalva ratio and E:I ratio also decreased, whereas orthostatic blood pressure fall increased. AHI demonstrated significant negative correlations with HRV (r=?0.52, p<0.001), Valsalva ratio (r=?0.41, p=0.003), and E:I ratio (r=?0.38, p=0.007), and a positive correlation with orthostatic blood pressure fall (r=0.46, p=0.001). Conclusion: OSA severity is associated with an integrated pattern of greater adiposity, increased nocturnal hypoxemic burden, cardiometabolic comorbidity, and progressive cardiovascular autonomic dysfunction. The observed reduction in parasympathetic indices and increase in orthostatic blood pressure response with increasing AHI suggest that autonomic impairment may represent an important physiological component of severe OSA. Comprehensive assessment incorporating anthropometric, cardiometabolic, oxygenation, and autonomic parameters may improve clinical phenotyping and cardiovascular risk stratification in patients with OSA. Keywords: Obstructive sleep apnea; Apnea–Hypopnea Index; Body mass index; Nocturnal hypoxemia; Oxygen desaturation index; Autonomic dysfunction; Heart rate variability; Cardiometabolic comorbidities; Cardiovascular risk