The rapid increase of clinical activity with the Sleep Apnea Syndrome created an urgent need for a more complete description of this condition. Clinical descriptions were derived from case series of severely afflicted patients. Limited epidemiologic data, however, indicated that symptoms and objective manifestations of Sleep Apnea Syndrome occurred commonly in the population. It was unknown whether subjects with these findings were unrecognized patients, premorbid individuals at risk, or normal subjects with no special impairments. There was a need to define the frequency of signs and symptoms of Sleep Apnea Syndrome in the general population, and to determine the health effects related to these findings.