Sleep disordered breathing occurring predominantly in rapid eye movement REM sleep (rapid-eye-movement-related sleep-disordered breathing, REM SDB) is present in 10 to 36% of patients undergoing polysomnography (PSG) for suspected obstructive sleep apnea (O'Connor et al. in Am J Respir Crit Care Med 161:1465-1472, 2000; Resta et al. in J Respir Medicine 99:91-96, 2005; Haba-Rubio et al. in Chest 128:3350-3357, 2005; Juvelekian and Golish, American Academy of Sleep Medicine, abstract, 2004). We hypothesize that REM SDB is an age-related condition in women and, additionally, more prevalent in women than in men. Subjects with REM SDB were identified retrospectively among 1,540 obstructive sleep apnea (OSA) patients with an apnea-hypopnea index (AHI) >or= 5. Inclusion criteria for REM SDB were age >18, AHI >or= 5, NREM AHI < 15, and REM AHI/NREM AHI > 2. PSG data included sleep latency, REM latency, total sleep time (TST), AHI, REM AHI, NREM AHI, and sleep stage percentages. Demographic data and medical and psychiatric histories were also obtained. Statistical comparisons were made between men and women and women older and younger than 55 years, a marker for menopausal status. Two hundred twenty-one subjects fulfilled the criteria for REM SDB, yielding a prevalence of 14.4%. Overall, female apneics had a significantly higher prevalence of REM SDB than did men (24.5 vs 7.9%; p < 0.001). Younger women had a significantly higher prevalence than did older women (27.2 vs 18.6%; p = 0.008); younger men had a significantly higher prevalence of REM SDB than did older men (9.9 vs 4.5%; p = 0.002). Women were significantly older and more obese than were men. Younger women were more likely to be depressed and were significantly more obese than were older women. REM SDB is more prevalent in women than in men and more prevalent in men and women younger than 55 than those older than 55. In this population, women are more obese and older than men, while younger women were more obese than older women. These descriptive distinctions suggest differences in mechanism which may depend on gender and age.