Short and long daily sleep duration were risk factors for dementia and premature death in a study of Japanese adults aged 60 years and older. The findings are published in the Journal of the American Geriatrics Society.

Among 1,517 adults who were followed for 10 years, 294 developed dementia and 282 died. Age- and sex-adjusted incidence rates of dementia and all-cause mortality were greater in those with daily sleep duration of less than 5.0 hours and 10.0 hours or more, compared with those with daily sleep duration of 5.0 to 6.9 hours. Participants with short sleep duration who had high physical activity did not have a greater risk of dementia and death, however.

"Given the beneficial effects of physical activity on risk of sleep disturbance, these findings indicate that not only maintenance of appropriate sleep duration, but also modification of lifestyle behaviors related to sleep may be an effective strategy for preventing dementia and premature death in elderly adults," the authors wrote.