Age, Sex, and Central Adiposity as Determinants of Autonomic Nervous System Reactivity in Adults

Background and Objectives: The autonomic nervous system (ANS) orchestrates adaptation to stress; however, its reactivity is influenced by demographic, anthropometric, and psychosocial factors. While arterial stiffness and central adiposity are established cardiovascular risk markers, less is known about how maladaptive coping strategies, cumulative life stress, and quality of life influence short-term autonomic regulation. This study examined the age- and sex-specific associations between anthropometry, maladaptive coping, life stress, quality of life, and ANS adaptation in adults. Materials and Methods: In this cross-sectional study, 122 healthy adults aged 21-78 years underwent a standardized lay-stand-lay (LSL) protocol with pulse wave analysis. Hemodynamic outcomes included pulse wave velocity (PWVao), augmentation indices (AIxA and AIxB), and aortic blood pressures (SBPao and PPao). Anthropometric measures comprised BMI, waist and hip circumference, waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR). Psychosocial assessments included the Young Hypercompensation Inventory (maladaptive coping), Holmes-Rahe Life Events Inventory (life stress), and EQ-5D-3L (quality of life). Associations were analyzed using mixed-effects models adjusted for covariates, with false discovery rate correction. Results: Age was the strongest determinant of autonomic reactivity: older adults showed greater recovery of augmentation indices and central pressures after orthostatic challenge. Sex differences were evident, with women displaying consistently higher augmentation indices and men showing greater PWV responses. Central adiposity (WHR, WHtR, and waist circumference) predicted blunted augmentation index reactivity, while hip circumference was protective. BMI-defined obesity showed weaker associations. Maladaptive coping, life stress burden, and quality of life were not significantly associated with ANS indices after correction for multiple comparisons. Conclusions: ANS adaptation to postural stress is largely determined by age, sex, and visceral adiposity, whereas psychosocial measures showed limited influence in this healthy adult sample. These findings highlight the demographic and anthropometric determinants of cardiovascular adaptability, suggesting that psychosocial influences may primarily act through long-term behavioral and neuroendocrine pathways.