Sex differences in sleep architecture and nocturnal oxygenation across obstructive sleep apnea severity: an observational hospital-based study.

BACKGROUND

Sex differences in obstructive sleep apnea (OSA) may extend beyond the apnea-hypopnea index (AHI), the standard measure of OSA severity, and involve differences in sleep architecture and nocturnal oxygenation. We compared these characteristics between women and men across OSA severity categories in a large Chinese clinical cohort.

METHODS

This single-center, hospital-based observational study included adults referred for overnight polysomnography at a sleep center in Fujian, China. OSA severity was classified as mild, moderate, or severe according to AHI. Outcomes included total sleep time (TST), sleep stages, sleep fragmentation, nocturnal oxygenation, respiratory event composition, and the relative distribution of oxygen desaturation events between rapid eye movement (REM) and non-REM sleep. Associations between sex, OSA severity, and these outcomes were examined using adjusted generalized linear models.

RESULTS

Among 1,632 patients (mean age 57 years; 41.4% women), women exhibited longer TST, a lower proportion of stage N1 sleep, a higher proportion of stage N3 sleep, and lower sleep fragmentation than men, irrespective of OSA severity (all p < .001). Men exhibited a higher proportion of REM sleep than women only in mild OSA (+ 1.46 percentage points, p = .009). Women showed a greater predominance of hypopneas than men in moderate and severe OSA (p = .02 and p < .001, respectively). Women also exhibited lower nadir oxygen saturation (SpO2) values than men across OSA severity categories (p = .001). In addition, women demonstrated a greater predominance of REM-related oxygen desaturation events than men in both moderate and severe OSA (both p < .001).

CONCLUSIONS

Women and men with similar OSA severity exhibited distinct patterns of sleep architecture, respiratory event composition, and nocturnal oxygenation. These findings suggest that characteristics beyond AHI may provide additional information regarding the physiological expression of OSA, although their clinical relevance remains to be determined.