Sleep duration and associated factors in a community sample of elderly individuals in Korea

Background This study estimates the duration of sleep and its relationships with clinical correlates in a community sample of elderly individuals in Korea. Methods A total of 1924 individuals aged 65 and over were interviewed in Korea. Sleep durations were classified into five categories: 5.00 h or less, 6.00 h per day, 7.00 h per day, 8.00 h per day, and 9.00 h or more per day. Sleep disturbance was classified into four sleep complaints: difficulty initiating sleep, difficulty maintaining sleep, early-morning awakening, and non-restorative sleep. The Mini-Mental Status Examination, the Geriatric Depression Scale, and questionnaires about the presence of cardiovascular disease were employed. Results The most frequent self-reported sleep duration was 7.00 h. The mean sleep duration was 6.46 h. Female subjects, subjects between the ages of 75 and 79, and subjects with current depression were associated with sleeping for 6.00 h or less or 9.00 h or more. Subjects who lived alone and those with cardiovascular disease were associated with sleeping for 5.00 h or less. Subjects aged 80 and over, formally educated subjects, current smokers, and subjects with cognitive dysfunction were associated with sleeping for 9.00 h or more. Sleep disturbances according to sleep duration has a U-shaped distribution. We found that all sleep disturbances were significantly related to sleep durations of 6.00 h or less compared to sleep durations of 7.00 h. We also found that non-restorative sleep was significantly related to sleep durations of 8.00 h or more compared to sleep durations of 7.00 h. Conclusion A relatively high prevalence of short or long sleep duration was identified. Various sociodemographic variables influenced sleep duration. Depression, cognitive dysfunction, and cardiovascular disease were associated with short or long sleep duration. Careful attention should be paid to the health of elderly individuals who are short or long sleepers.