Sleep disorders and the risk of cognitive decline or dementia: an updated systematic review and meta-analysis of longitudinal studies.

BACKGROUND

The evidence on the relationship between sleep disorders and the risk of cognitive decline or dementia remains inconsistent.

OBJECTIVES

This systematic review and meta-analysis aimed to provide updated evidence on the association between sleep disturbances and cognitive decline.

METHODS

PubMed, EMBASE, and Web of Science were systematically searched from their respective inceptions to 18 February 2025. Cohort studies investigating longitudinal associations between sleep disorders and cognitive decline or dementia were included. Pooled relative risks (RRs) with 95% confidence intervals were calculated. Sensitivity analyses were conducted to evaluate the robustness of the pooled estimates. Publication bias was assessed using Egger's and Begg's tests, and meta-regression analysis was performed to explore potential sources of heterogeneity across studies.

RESULTS

Seventy-six eligible cohort studies with eight types of sleep disturbances were included in the meta-analysis. Insomnia was associated with an increased risk of dementia (RR = 1.13). Both short sleep duration (7 h; RR = 1.27) and long sleep duration (8 h; RR = 1.23 for cognitive decline, RR = 1.43 for all-cause dementia, and RR = 1.66 for Alzheimer's disease (AD) were significant risk factors for cognitive decline and dementia. Excessive daytime sleepiness significantly increased the risks of vascular dementia (VD) (RR = 1.85), all-cause dementia (RR = 1.41), and cognitive decline (RR = 1.37). Sleep-related movement disorders indicated the strongest association, markedly increasing the risk of VD (RR = 2.53). Poor sleep quality was also a significant risk factor for AD (RR = 1.24), all-cause dementia (RR = 1.17), and cognitive decline (RR = 1.18).

CONCLUSION

This meta-analysis highlights sleep management as a pivotal modifiable factor in reducing the risk of all-cause cognitive decline. Systematic screening and early intervention for sleep disturbances should be prioritized as essential preventive strategies in clinical populations.