(CIT): The National Center on Sleep Disorders Research (NCSDR), located within the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH), was established in 1993 to combat a serious public health concern. About 70 million Americans suffer from sleep problems; among them, nearly 60 percent have a chronic disorder. Each year, sleep disorders, sleep deprivation, and sleepiness add an estimated $15.9 billion to the national health care bill. Additional costs to society for related health problems, lost worker productivity, and accidents have not been calculated. Sleep disorders and disturbances of sleep comprise a broad range of problems, including sleep apnea, narcolepsy, insomnia, parasomnia, jet-lag syndrome, and disturbed biological and circadian rhythms.