Persons with sleep apnea syndromes experience 10 or more episodes per hour of sleep during which airflow ceases for more than 10 seconds. Sleep apnea syndromes are classified as obstructive, central or mixed: obstructive when the respiratory muscles continue to contract but airflow is not obtained, central when respiratory effort is not present, and mixed when elements of both obstructive and central apnea are present. Approximately 4 percent of adult men and 2 percent of adult women are believed to have these conditions. In addition to having symptoms such as snoring, headaches, depression, decreased libido and fatigue, patients with sleep apnea are at risk for a range of severe complications secondary to recurrent hypoxia and hypercapnia during sleep. Diagnosis may require an overnight polysomnogram in addition to the history, a physical examination and a laboratory assessment. Less cumbersome diagnostic modalities are being developed. Treatment options include weight reduction, change in sleeping position, avoidance of sedatives, use of continuous positive airway pressure and surgical treatment.