Apnea is associated with either a fall in oxyhemoglobin desaturation or an arousal from sleep.
Hypopneas, which are defined as partial reductions in airflow associated with falls in oxygen saturation or arousals from sleep, are also recorded. The sleep apnea syndrome has been clinically defined as recurrent apnea or hypopnea associated with clinical impairment usually manifested as increased daytime sleepiness or altered cardiopulmonary function. Some studies have suggested that the prevalence of sleep apnea in women increases after menopause. At present, no published epidemiologic studies have examined the relationship between race and sleep apnea. Given the high prevalence of obesity among specific populations and minorities, sleep apnea may be highly prevalent in these groups.