Correlates of obstructive apnea duration

Purpose: The duration of an obstructive apnea is dependent on gender, age, body position, and state. Termination of an obstructive respiratory event is attributed as the end result of an achieved specific negative inspiratory force, sufficient to result in cortical arousal. We used polysomnographic measures of tendency for arousal, hypothesizing that long apnea would be associated with a smaller tendency for arousal. Methods: From a clinical sleep laboratory sample, 140 subjects (82 men) with an obstructive apnea index >5 were selected. Subjects were split into those with long and short apnea by stratifying around median obstructive apnea duration. Those with long duration apnea were compared to short apnea for age, gender, apnea-hypopnea index (AHI), and a measure of tendency to arouse, respiratory event-related arousal to AHI ratio (RespArI:AHI). Results: Obstructive apnea duration (mean ± SD) was 20.7 ± 5.6. Apnea duration trended toward being longer in men than women and was significantly longer in supine than nonsupine sleep (19.2 ± 7.3 vs. 16.1 ± 10; p = 0.001) and REM than NREM sleep (24.3 ± 9.0 vs. 19.7 ± 5.1; p < 0.001). Those with long compared with short apnea were significantly older; AHI was similar. RespArI:AHI was significantly higher for those with long compared with short apnea (0.58 ± 0.24 and 0.43 ± 0.19; p < 0.0001). This difference was most apparent for women in whom RespArI:AHI for those with long and short apnea was 0.6 ± 0.24 and 0.41 ± 0.17 (p = 0.001). For men, RespArI:AHI for those with long and short obstructive apnea was 0.56 ± 0.24 and 0.44 ± 0.2 (p = 0.02). Conclusions: Long obstructive apnea duration occurs to a greater degree in older individuals, in supine, and REM sleep. Women more than men with long apnea had a greater tendency toward arousal.