The mediating role of daily living ability and sleep in depression and cognitive function based on a structural equation model.

backgroundThe incidence of depression and cognitive dysfunction is high in the elderly population, which incurs serious social burden. In recent years, an increasing number of studies have found that poor sleep quality and impaired daily activities in the elderly are also closely related to these two diseases.To explore the mediating role of sleep quality and daily activity ability in the elderly's cognition and depression. It extends upon existing research and provides evidence for new areas of intervention that may ameliorate and delay cognitive decline in the elderly.

methodsData were collected from a representative sample of 5,470 (aged 60 years and above) in Anhui Province from the 2019 Anhui Health and Life Expectancy Survey(AHLS). Cognitive function was assessed by the Mini-Mental State Examination(MMSE), depression symptoms by the Patient Health Questionnaire(PHQ-9), physical function by the Barthel Index for Activities of Daily Living, and sleep quality by the Pittsburgh Sleep Quality Index(PSQI). Descriptive analysis was conducted for the distribution of various covariates and results. Pearson correlation analysis was employed to test the relationship between depression symptoms, cognition, poor sleep quality and daily living ability of the elderly. The structural equation model was used to explore the link between depression and cognition in the older adults, and to test mediating effects of daily activity and sleep disturbance on depression and cognition.

resultsAmong all participants, the average cognitive score was 21.51 (SD = 6.10), and the incidence of depression symptoms was 31.6%. Depression symptoms had a significant direct impact on cognition (β= -0.075, 95%CI=-0.099, -0.050). Depression symptoms was related to poor sleep quality and daily living ability (β = 0.420, 95%CI = 0.409, 0.447; β=-0.161, 95%CI=-0.163, -0.113). Cognition was also related to both factors (β=-0.042, 95%CI=-0.070, -0.024; β = 0.143, 95%CI = 0.112, 0.173). The ability of daily living was related to poor sleep quality (β=-0.049, 95%CI=-0.079, -0.027). Poor sleep quality and daily living ability mediated the relationship between depression symptoms and cognition (β=-0.020, 95% CI=-0.025, -0.014; β=-0.020, 95%CI=-0.030, -0.010).

conclusionsThis study found that depression symptoms in the older adults was significantly related to cognitive function. Older adults with depression symptoms are more likely to have cognitive impairment. In addition, poor sleep quality and the ability of daily living can play a mediating role between depression and cognition. In the future, the society should pay attention to the mental health of the elderly to avoid depression. They should also pay attention to the impact of their sleep quality and daily activity ability, so as to better maintain cognitive function.