In 1990, there was increased recognition that obstructive sleep apnea occurs commonly and may lead to serious adverse cardiopulmonary and psychoneurologic health effects. In subjects with numerous and prolonged apneas, nocturnal hypoxemia and disrupted sleep may lead to pulmonary hypertension, cor pulmonale, and excessive daytime sleepiness. Systemic hypertension is more prevalent in subjects with obstructive sleep apnea than in the general population. The health consequences of less severe disease have not been extensively studied in the context of general population studies. However, snoring, a symptom related to sleep apnea, may double the risk of ischemic heart disease. The prevalence of systemic hypertension is higher in snorers than in nonsnorers, a finding potentially of considerable public health concern. An increased number of deaths due to cardiovascular disease in elderly subjects with disordered breathing during sleep also has been demonstrated.