In order to establish the prevalence in women with reasonable precision, the prevalence study employed a two-stage sample modified from the prevalence study in men in the following two ways: an expanded telephone sample (N=12,219 women) selected randomly from the general population was evaluated, for clinically relevant risk factors for sleep apnea; and 2) a second sample (N=1,000) selected randomly from the first sample based on higher risk for sleep apnea (including the additional risk factor of menopause) was evaluated in the sleep laboratory to determine the presence of sleep apnea. This strategy yielded an adequate power in order to establish the prevalence of sleep apnea requiring treatment and sleep disordered breathing in women in the general population as well as result in a large enough sample to establish the association between risk factors and sleep apnea in women. In order to perform gender analyses, the study compared previously published data from a total of 4,364 men interviewed in an expanded telephone sample and 741men evaluated in the sleep laboratory.