Sleep and sleep disorders are different in several important ways between men and women. Because of pregnancy and menopause, women experience changes in sleep that may present as clinical problems. In clinical populations, women are more likely to present with insomnia than are men, although their sleep may be better preserved. The presentation of sleep apnea in women is distinct from that of men and is less likely to include a "classic" history of witnessed ap-nea or heavy snoring. More likely it presents with nonspecific symptoms, such as fatigue or mood disturbance. There are little data on the effects of different treatments for OSA between men and women. OHS is a syndrome that may be as common in women as in men. The role of hormones in its pathophysiology is not well-defined.