Gender differences in sleep apnea severity are diminished during REM sleep

Background: It has been shown previously that sleep apnea (SA) is substantially more common and more severe in men than women. Yet, the precise pathophysiological mechanisms accounting for gender differences in SA remain less well understood. Method: A retrospective chart review was performed on patients who underwent in-lab polysomnography between January 2009 and December 2010 to examine the influence of gender on the polysomnographic features of SA. From 227 consecutive adults who met inclusion criteria, we identified 46 male-female pairs matched individually for age (mean±SD 52±9 years) and BMI (31±6 kg/m 2 ). Results: Despite similarities in age, BMI, sleep efficiency, and Epworth Sleepiness Scale score, men had higher total apnea-hypopnea index (AHI) [median (interquartile range) 21.3 (8.6-43.4) vs. 8.8 (1.7-26) events/h; P P P =0.007]. Surprisingly, there was no statistical difference in AHI during REM sleep between men and women [21.3 (7-46.7) vs. 14.3 (2.1-45.8) events/h; P =0.662]. In addition, compared to men, women had a significantly higher difference between REM-AHI and NREM-AHI ( P =0.023). Conclusions: To conclude, SA is less severe in women than men because of milder SA during NREM sleep, which is independent of age and BMI. Our findings indicated that severity of SA is similar in men and women during REM sleep, suggesting differences between the sexes in upper airway function during sleep in adults with SA.