Researchers in Japan followed 1,517 adults without dementia for 10 years.
Incident rates of dementia and all-cause mortality were significantly greater in subjects who slept less than 5 hours per day or 10 or more hours per day.
Therefore, short AND long daily sleep duration are risk factors for dementia and death in adults age 60 and older.
J Am Geriatr Soc. 2018 June 6