Excessive daytime sleepiness among the Japanese general population.

Background: Excessive daytime sleepiness is one of the principal symptoms of sleep disturbances, and is often associated with serious consequences including traffic and industrial accidents, decreased productivity, and interpersonal problems. However, there are few epidemiologic studies on excessive daytime sleepiness in a large scale sample targeting Japanese general population.

Methods: The survey was performed using a self-administered questionnaire in June 2000, targeting a population randomly selected from among 300 communities throughout Japan. This questionnaire included information about sleep habits and sleep problems. Excessive daytime sleepiness measured according to a question "Do you fall asleep when you must not sleep (for example when you are driving a car)?"

Results: A total of 28,714 subjects completed the questionnaire. The prevalence of excessive daytime sleepiness was 2.5% (male=2.8% and female=2.2%). Backward elimination analysis showed that the following were associated with excessive daytime sleepiness: male sex, young age, short sleep duration, subjective insufficient sleep, loss of deep sleep, disagreeable sensations in the legs, interruption of sleep by snoring or dyspnea, and feeling psychological stress. Interruption of sleep by snoring or dyspnea was the strongest associated factor (adjusted odds ratio=2.46, 95% confidence interval=1.76-3.43) of excessive daytime sleepiness.

Conclusions: These results suggest that excessive daytime sleepiness in Japanese is associated with several sleep problems. These findings may be useful in attempts to prevent excessive daytime sleepiness in the general population of Japan.