Our study affirms previous findings that REM SDB is more prevalent in women than men (40.8% vs 20.1%), while adding new information regarding the relations among REM SDB, gender, age, and obesity. According to our data, the female predilection toward REM SDB occurs irrespective of sleep position across all adult ages and ranges of BMI. There may be a greater discrepancy in the earlier decades because REM SDB prevalence decreases more rapidly with age in women than men (age and sex interaction, p = 0.063). REM SDB prevalence is also moderated by obesity and sex (BMI and sex interaction, p = 0.061), decreasing with increasing obesity severity more so in men than women. So at any adult age and at any level of BMI, REM SDB is more likely to occur in a woman; however, among respective gender categories, REM SDB expression is more associated with younger age for women and lower BMI for men.
Examination of REM AHI/NREM AHI by gender and age revealed a very similar pattern, showing higher values for women. However, unlike REM SDB prevalence, REM AHI/NREM AHI ratio was found to decline with age only in women, remaining fairly constant in men. Further, in women REM AHI/NREM AHI declined more quickly in women > 52 years old. We introduce REM AHI/NREM AHI as a new marker identifying the extent to which respiratory events are confined to REM sleep; however, this measure is limited by a lack of specificity in that an elevated value may result from a high REM AHI, low NREM AHI, or a combination of the two scenarios. Indeed, when comparing male and female subjects with and without REM SDB, women had a higher REM AHI/NREM AHI resulting from a combination of a lower NREM AHI and higher REM AHI.