DESCRIPTION: (abstract adapted from the applicants abstract) The National Commission on Sleep Disorders Research identified excessive daytime sleepiness (EDS) as a public health problem. Although clinical information about its determinants, morbidity, and significance is emerging, little population-based information about the prevalence, consequences and risk factor's of EDS exists. The research plan of the NIH Center on Sleep Disorders Research calls for "epidemiological research to define the prevalence, etiology, risk factors, morbidity, and costs of EDS in the general population." This application directly addresses these needs. The limited epidemiological studies of determinants and correlates of sleepiness suggest some findings that are consistent with the laboratory data (e.g. snoring), but some that are inconsistent with the laboratory data (eg. depression). Understanding discrepancies between laboratory and epidemiological data is important to public health and safety. Sleepiness is serious and life-threatening, due to both its direct consequences (i.e., automobile crashes and industrial accidents) and its associated diseases (i.e., obstructive sleep apnea or depression). This proposal links sleep laboratory methods and research information on daytime sleepiness to the rigorous sampling, field assessment, and recruitment methods of epidemiology research. Thereby, it builds on the strengths and minimizes the weaknesses of each method (e.g., potential biases of clinical samples and errors in self- reports of,surveys) to assess the prevalence, consequences, and risk factors of sleepiness. The goals of the study are to estimate the prevalence of EDS in the general population, as assessed by the MSLT, to relate MSLT-defined daytime sleepiness to laboratory performance and automobile crashes, and to identify risk factors for EDS. Toward these goals, the research design is composed of two components: 1) a random digit dial, computer assisted telephone survey (n = 3,270) and 2) a laboratory based evaluation (n = 872). The telephone survey will define the frame from which a representative sample of subjects will be selected for laboratory study. Additionally, the survey will collect data on sleep habits, self-report measures of daytime sleepiness, and suspected risk factors. Subsets of the survey sample will be recruited to the laboratory to measure daytime sleepiness, using the MSLT, physical characteristics predictive of EDS, and performance on psychomotor tests. The important contribution of the present proposal is that it will be the first population-based study to use laboratory assessments, its consequences and risks to measure sleepiness.