As a part of an epidemiologic survey of dementia in a community of aged persons, correlation between sleep complaints and physical illness and senility were studied. A total of 3302 randomly sampled aged individuals Japanese Society of Sleep Research 191(aged 2 65 years) were studied using a questionnaire. In this sample the prevalence of poor sleep and habitual snoring did not increase with age. The prevalence of excessive daytime sleepiness showed an increase with age. Male predominance of habitual snoring and female predominance of poor sleep were observed. Female predominance of excessive daytime sleepiness was noted among the aged 70 and over. Age-related excessive daytime sleepiness was significantly correlated with senility. Key wordselderly, excessive daytime sleepiness, sleep complaints, senility, stratified random sampling. INTRODUCTIONThe correlation between sleep problems and general health impairments has been reported,' but there is no report on the interrelation between sleep coniplaints and senility. In order to estimate the prevalence of sleep complaints in relation to physical illness and senility, we conducted an epidemiologic survey using a stratified random sampling method. SUBJECTS AND METHODA questionnaire survey was completed by all attendees of the aged community dwelling in Aichi Prefecture of Japan. Both target population and responders were virtually representative of the Japanese population in relation to gender and age (65+ years) characteristics. The sample as randomly drawn from the resident register (n = 801 536) in April 1995 and yielded 3302 persons aged 65 or over (1485 men and 1817 women). The subjects responded to the structured multi-item questionnaire involving demographic data, physical conditions, mental conditions, social activities and sleep problems. Sleep problems included difficulty sleep, excessive daytime sleepiness (EDS), habitual snoring (HS), witnessed apnea during sleep and the use of sleeping pills. Four grade answer: 'always', 'often', 'rarely' and 'no' were marked in each item. From these data, the prevalence of sleep disturbances were estimated and the correlation between sleep complaints and physical or mental health problem were analyzed using a Chi-squared test. The terni 'senility' is used according to DSM-III-R.2 In our epidemiologic survey, senility is deemed almost same as dementia. RESULTSOf these 3302 aged subjects, 2060 had some physical illnesses (male : female 62.7 : 62.1%), 965 showed senility (30.6 : 28.1%), 567 had alcohol drinking habit (35 : 2.6%), and 685 showed smoking habit (36.4 : 7.9%). The prevalence of poor sleep, EDS, HS, witnessed apnea and habitual use of sleeping pills were 16.9, 4.6, 8.9, 0.72 and 4.5%, respectively. About 22% of women and 18% of men complained of trouble sleeping. Significantly, female predominance was noted in the prevalence of poor sleep. Poor sleep was significantly correlated with physical illnesses such as hypertension and rheumatoid arthritis. As shown in Fig. 1 , the prevalence of HS showed a de...