In a recent telephone survey of more than 4,000 British individuals aged 15 years or older, more than 5% reported severe daytime sleepiness and more than 15% reported moderate daytime sleepiness. It is likely that daytime sleepiness deleteriously affects work activities, social and/or marital life, and exhibits a negative socioeconomic impact. Results of a number of studies including this one suggest a link between sleepiness and accidents. In this survey, motor vehicle accidents or mishaps involving operation of machine tools occurred twice as often in the subjects with a history of moderate or severe daytime sleepiness as in the general population without daytime sleepiness. Among the factors associated with daytime sleepiness were female gender, middle age, high caffeine consumption, difficulty sleeping, sleep apnea or leg pain during sleep, and depression.

Archives of Internal Medicine December 1997;157:2645-2652