Non-REM Apnea and Hypopnea Duration Varies across Population Groups and Physiologic Traits.

Symptoms and morbidities associated with obstructive sleep apnea (OSA) vary across individuals and are not predicted by the apnea-hypopnea index (AHI). Respiratory event duration is a heritable trait associated with mortality that may further characterize OSA. We evaluated how hypopnea and apnea durations in non-REM (NREM) sleep vary across demographic groups and quantified their associations with physiological traits (loop gain, arousal threshold, circulatory delay, and pharyngeal collapsibility). Data were analyzed from 1,546 participants from the Multi-Ethnic Study of Atherosclerosis with an AHI ≥5. Physiological traits were derived using a validated model fit to the polysomnographic airflow signal. Multiple linear regression models were used to evaluate associations of event duration with demographic and physiological factors. Participants had a mean age ± SD of 68.9 ± 9.2 years, mean NREM hypopnea duration of 21.73 ± 5.60, and mean NREM apnea duration of 23.87 ± 7.44 seconds. In adjusted analyses, shorter events were associated with younger age, female sex, higher body mass index ( < 0.01, all), and Black race ( < 0.05). Longer events were associated with Asian race ( < 0.01). Shorter event durations were associated with lower circulatory delay (2.53 ± 0.13 s,  < 0.01), lower arousal threshold (1.39 ± 0.15 s,  < 0.01), reduced collapsibility (-0.71 ± 0.16 s,  < 0.01), and higher loop gain (-0.27 ± 0.11 s,  < 0.05) per SD change. Adjustment for physiological traits attenuated age, sex, and obesity associations and eliminated racial differences in event duration. Average event duration varies across population groups and provides information on ventilatory features and airway collapsibility not captured by the AHI.