There are few epidemiological studies on sleep loss and daytime sleepiness
in the general adult population of Japan. A total of 4000 adult people, age
d 20 and over, were randomly drawn from five areas of Japan, and 3030 indiv
iduals were interviewed and completed a questionnaire including information
about sleep duration and sleep problems. Overall, 29% slept less than 6 h
at night, 23% reported having insufficient sleep, and 6% took sleep enhanci
ng medications. The prevalence rates were 21% for symptoms of insomnia and
15% for excessive daytime sleepiness. Symptoms of insomnia were more preval
ent in the elderly, whereas young people were more likely to report short s
leep duration, subjective insufficient sleep and excessive daytime sleepine
ss. A multiple logistic regression model revealed that excessive daytime sl
eepiness had significant associations with young people, short sleep durati
on, insomnia symptoms, subjective insufficient sleep and sleep enhancing me
dication use. Short sleep duration was the strongest predictor of excessive
daytime sleepiness. The findings indicate that sleep loss and excessive da
ytime sleepiness in the Japanese adult population are common, and comparabl
e to those reported in Western countries. Excessive daytime sleepiness in t
he general adult population seems more likely to be attributed to short sle
ep duration. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.