Excessive sleep duration increases the risk of dementia among older Chinese adults: evidence from the CLHLS

Abnormal sleep duration represents a significant contributor to dementia; however, this association has not been explored among the elderly Chinese population. Therefore, this study investigated the relationship between sleep duration and dementia among the Chinese elderly population.

Data were obtained from the Chinese Longitudinal Healthy Longevity Survey (CLHLS). This study included 7,680 participants aged 65 years and older at baseline in 2011. Cox proportional hazards models were performed to determine the relationship between sleep duration and dementia risk in this patient population.

Over a total follow-up period of 28,147 person-years, 398 dementia cases were identified. The mean age of participants was 85.55 ± 11.09 years, with female predominance (54.71%). Participants with optimal sleep duration (6-8 h) had a significantly lower risk of dementia than those with excessive sleep duration (> 10 h) (P < 0.001, log-rank test). In the fully adjusted Model 3, participants with excessive sleep durations at baseline were associated with an 82% higher risk of dementia (HR = 1.82, 95% CI = 1.25-2.65) compared with the reference group. Tests for nonlinearity between sleep duration and dementia were not significant (P = 0.06). No significant interactions were found between sleep duration and sex, age, residence, or marital status. Finally, the sensitivity analysis demonstrated the stability of these findings.

Overall, the present study findings demonstrate that excessive sleep duration (over 10 h) is an independent predictor of increased risk of dementia among older Chinese adults. Conversely, maintaining a moderate sleep duration of 6 to 8 h appears to be a protective factor, correlating with a lower incidence of the condition.