Abstract P273: The Association of Obstructive Sleep Apnea on Cardiac Parasympathetic Responses During Stress Testing: The Multi-Ethnic Study of Atherosclerosis (MESA)

Introduction: Obstructive sleep apnea (OSA) may lead to abnormalities in the balance between sympathetic and parasympathetic activity at night; variation in daytime activity and responses to stress are less understood. Hypothesis: OSA is associated with reduced parasympathetic response from stress challenges. Method: In the Multi-Ethnic Study of Atherosclerosis (MESA) cohort (mean age 68yrs), 413 participants underwent in-home polysomnography. OSA severity was characterized by apnea-hypopnea index (AHI) as mild (5≤AHI<15), moderate (15≤AHI<30), severe (AHI≥30), or no OSA (AHI <5 events/h) (referent). We examined High Frequency (HF)-heart rate variability (HRV), an index of cardiac parasympathetic modulation, during a standardized daytime stress challenge protocol: a baseline period followed by two mental stress tasks, the modified Stroop color-word conflict and an arithmetic task, each followed by a recovery period. We used linear mixed effects model with HF-HRV as outcome. Results: Participants with mild OSA (but not those with moderate or severe OSA) had lower levels of HF-HRV than those with no OSA (–0.36 log msec 2 , 95% CI –0.70, –0.02, P <0.05) at baseline. Those with severe OSA had a smaller increase in HF-HRV during recovery than the no OSA group (–0.34% change, 95% CI –0.63, –0.06, P <0.05) ( Table 1A ). Because OSA related cardiovascular disease may vary by age, a sensitivity analysis separately examining participants ≥65 and < 65 yo suggested that those ≥65 years with mild and moderate OSA had greater HF-HRV reactivity to the tasks than those with no OSA, and those <65 years with mild, moderate and severe OSA had a smaller increase in HF-HRV during recovery than those without OSA ( p -interaction=NS) (Table 1B). Conclusions: Our results showed reduced HRV at baseline and a decrease of the parasympathetic cardiac modulation with stress challenge associated with OSA severity. Findings were different according to age groups. Assessment of HRV may help identify individuals with OSA-related physiological abnormality.