Zhang Q, Wu Y, Liu E, et al. - In this longitudinal study involving 2,148 elderly people (the baseline including 43.16% aged 70-79, 23.79% aged 80 and over), long or short sleep duration is linked to the five cognitive domains that show cognitive decline, making sleep duration a modifiable risk factor for cognitive decline. Such findings point to the necessity for intervention approaches to help Chinese older persons maintain optimal sleep durations.

• Sleep duration and global cognition and cognitive domains have an inverted U-shaped association, with the maximum cognitive scores observed for sleep duration between 6 and 9 hours and the slope evolving from smooth to steeper from 2005 to 2014.

• According to the regression model, long sleep duration (> 9 h) is significantly linked to global cognition and four cognitive domains: orientation, attention and calculation, immediate recall and visual construction.

• Both long and short sleep durations are associated with delayed recall but not with category fluency, language, or the ability to follow a three-stage command.

• The five cognitive domains associated with sleep duration showed the fastest rate of decline.