Excessive sleep duration (over 10 hours) is an independent predictor of increased risk of dementia among older Chinese adults, while maintaining a moderate sleep duration of 6 to 8 hours appears to be a protective factor.
Key Findings
Results
Participants with excessive sleep duration (>10 hours) had an 82% higher risk of developing dementia compared to those with optimal sleep duration (6-8 hours).
HR = 1.82, 95% CI = 1.25–2.65 in the fully adjusted Model 3
Participants with optimal sleep duration (6–8 hours) had a significantly lower risk of dementia than those with excessive sleep duration (P < 0.001, log-rank test)
This association held after full adjustment for covariates
Sensitivity analyses demonstrated the stability of these findings
Methods
Over the follow-up period, 398 dementia cases were identified among 7,680 older Chinese adults.
Total follow-up period was 28,147 person-years
Participants were aged 65 years and older at baseline in 2011
Mean age of participants was 85.55 ± 11.09 years
Female predominance in the sample (54.71%)
Data were drawn from the Chinese Longitudinal Healthy Longevity Survey (CLHLS)
Results
The relationship between sleep duration and dementia risk did not show statistically significant nonlinearity.
Test for nonlinearity between sleep duration and dementia was not significant (P = 0.06)
This suggests the association may follow a more linear pattern rather than a U-shaped curve
Results
No significant interactions were found between sleep duration and sex, age, residence, or marital status in relation to dementia risk.
Subgroup analyses tested interactions with sex, age, residence, and marital status
None of these variables significantly modified the association between sleep duration and dementia
This suggests the association between excessive sleep and dementia risk is consistent across these demographic subgroups
Methods
Cox proportional hazards models were used to assess the relationship between sleep duration and dementia risk in this elderly Chinese cohort.
Multiple models were constructed, with Model 3 being the fully adjusted model
The reference group for comparisons was participants with optimal sleep duration (6–8 hours)
Baseline sleep duration was assessed in 2011 as part of the CLHLS survey
The study population was restricted to adults aged 65 years and older
What This Means
This research studied the relationship between how long older Chinese adults sleep and their risk of developing dementia. Using data from nearly 7,700 people aged 65 and older who were followed over several years, researchers found that those who slept more than 10 hours per night were significantly more likely to develop dementia compared to those who slept a moderate 6–8 hours. Specifically, excessive sleepers had an 82% higher risk of developing dementia over the follow-up period.
The study also found that sleeping 6–8 hours per night was associated with a lower incidence of dementia, suggesting this range may be protective for brain health in older adults. Importantly, the link between excessive sleep and dementia risk was consistent regardless of a person's sex, age, where they lived, or marital status, strengthening the generalizability of the findings within this population.
This research suggests that sleep duration — particularly sleeping too much — may be an important and measurable indicator of dementia risk among elderly individuals in China. Since sleep habits are potentially modifiable, these findings could have relevance for identifying at-risk older adults. However, the study cannot confirm whether excessive sleep causes dementia or whether early-stage dementia causes people to sleep more, which is an important limitation to consider when interpreting the results.
Fan Z, Liu X, Lu X, Wu Y, Zhou M. (2026). Excessive sleep duration increases the risk of dementia among older Chinese adults: evidence from the CLHLS.. BMC geriatrics. https://doi.org/10.1186/s12877-026-07159-6