B31-15 Heart Rate Variability and Obstructive Sleep Apnea Severity in a Multi Ethnic Asian Cohort

Abstract Rationale Obstructive sleep apnea (OSA) is characterized by repeated episodes of complete or partial airway obstruction during sleep. Beyond the respiratory consequences, OSA is associated with autonomic dysfunction and elevated cardiovascular risk.1 Heart rate variability (HRV) provides a non-invasive measurement of autonomic function, encompassing both time-domain and frequency-domain indices. Timedomain indices, such as the standard deviation of normal-to-normal (NN) intervals (SDNN) and the root mean square of successive differences (RMSSD) reflect overall variability and parasympathetic activity, respectively.2 Frequency-domain indices, such as low-frequency (LF, 0.04-0.15Hz) power, high frequency (HF, 0.15-0.40Hz) power, and the LF/HF ratio, which together characterize sympathovagal balance.3 Prior studies examined HRV-OSA relations in Western cohorts.4,5 We examined these associations in a multiethnic Asian cohort. Methods A retrospective analysis of diagnostic polysomnography data from 133 subjects was conducted. HRV indices (SDNN, RMSSD, log-transformed LF and HF power, and LF/HF ratio) were derived from overnight ECG recordings using Compumedics Profusion 4 software and summarised as whole-night averages. OSA severity was classified by apnea-hypopnea index (AHI) thresholds: No OSA (<5 events/h), Mild (5-14), Moderate (15-29), and Severe (≥30). Associations between HRV indices and AHI were assessed using Pearson and Spearman correlation coefficients. Group differences across OSA severity categories were evaluated using Welch’s ANOVA. Statistical significance was set at p < 0.05. Results LF/HF ratio showed a modest but consistent positive association with AHI (Pearson r = 0.21, p = 0.017; Spearman ρ = 0.27, p = 0.004). Group comparisons confirmed this pattern, with LF/HF ratio differing significantly across OSA severity categories (Welch’s ANOVA p = 0.047). In contrast, RMSSD, SDNN, logHF, and logLF were not significantly correlated with AHI (all p > 0.05), apart from a borderline negative trend for logHF (Spearman ρ = -0.17, p = 0.047). These findings indicate that as OSA severity increases, autonomic balance shifts toward sympathetic predominance, reflected by higher LF/HF ratios. Conclusion The consistent association between LF/HF ratio and OSA severity observed in our cohort aligns with prior studies, which have similarly identified LF/HF as a sensitive marker of autonomic dysregulation in OSA.1,6 The progressive rise in LF/HF with increasing AHI supports the concept that intermittent hypoxia and arousals in OSA drive sympathetic activation and vagal withdrawal. These mechanisms may underlie the elevated cardiovascular risk in this population. The absence of consistent associations for other HRV indices highlights the exploratory nature of this study and suggests that HRV is influenced by confounders such as age, sex, and BMI.2,3 This abstract is funded by: None