Longitudinal associations between sleep duration and cognitive function in the elderly population in China: A 10-year...

Sleep duration is increasingly recognized as an important determinant of cognitive function among elderly. However, longitudinal studies on the relationship between sleep duration and cognitive function in Chinese elderly are rare. We sought to investigate the longitudinal association between sleep duration and cognitive function in Chinese elderly during a 10-year follow-up.

This longitudinal study analyzed 2148 elderly (the baseline including 43.16% aged 70%-79%, 23.79% aged 80 and over) who had participated in four waves of the Chinese Longitudinal Healthy Longevity Survey during 2005-2014. Cognitive function (including global functioning and cognitive domains) was assessed using the Chinese version of the Mini-Mental State Examination. Sleep duration was assessed via self-reports. Mixed model analysis was used to evaluate the association between sleep duration and cognitive function, adjusting for sociodemographic variables and risk factors for cognitive function.

There is an inverted U-shaped relationship between sleep duration and global cognition and cognitive domains, with the highest cognitive scores observed for sleep durations between 6 and 9 h and the curve shifting from smooth to steeper from 2005 to 2014. The regression model showed that long sleep duration (>9 h) is significantly associated with global cognition and four cognitive domains: orientation, attention and calculation, immediate recall and visual construction. Both long and short sleep durations are significantly associated with delayed recall and not significantly associated with category fluency, language or the ability to follow a three-stage command. The five cognitive domains related to sleep duration are the domains that exhibited a rapid rate of decline.

Sleep duration can be identified as a modifiable risk factor for cognitive decline, as long or short sleep duration is associated with the five cognitive domains that exhibit cognitive decline. These findings suggest the need for intervention measures to maintain healthy sleep durations among Chinese elderly people.