BREATHING AND OXYGENATION DURING SLEEP ARE SIMILAR IN NORMAL MEN AND NORMAL WOMEN

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Abstract
Most patients with the sleep apnea syndrome are male and there is a fundamental sex difference in breathing during sleep. Overnight ear O2-saturation (SaO2), breathing patterns and EEG sleep storage were measured in 21 healthy nonobese women (10 premenopausal, 11 postmenopausal) and in 19 healthy nonobese men of similar age. Sleep duration averaged 6 h 51 min (range 343-468 min). The 21 older (> 45 yr) subjects had more episodes of apnea and hypopnea (P < 0.01) and became more hypoxemic (P < 0.02) than did the 20 younger subjects, but there was no sex difference, either in the younger or older subjects, in irregular breathing or nocturnal hypoxemia. Seven subjects 51-68 yr of age (4 men and 3 women) had > 30 episodes of apnea and/or hypopnea and/or SaO2 decreases < 90%, but the clinical importance of this finding is unclear, 6 or the 7 being alive and 5 asymptomatic at an average of 47 mo. (range 5-67) later. Thus irregular breathing and hypoxemia during sleep are common in both sexes > 50 yr of age. Previous reports of a sex difference are probably explained by poor matching of the men and women, particularly with regard to body weight.