Sleep Duration and the Risk of Dementia: A Systematic Review and Meta-analysis of Prospective Cohort Studies.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of prospective cohort studies
PubMed 31604673 · doi:10.1016/j.jamda.2019.06.009
What was done
Authors conducted a systematic review and meta-analysis of prospective cohort studies from PubMed, EMBASE, and Web of Science. They assessed the association between sleep duration (short or long vs normal) and risks of all-cause dementia or Alzheimer's disease (AD) using a random-effects generic inverse-variance method.
What was found
The meta-analysis included 7 studies for all-cause dementia and 6 studies for AD. - Long sleep duration was significantly associated with an increased risk of all-cause dementia (HR = 1.77, 95% CI: 1.32-2.37) and AD (HR = 1.63, 95% CI: 1.24-2.13). - Short sleep duration showed no statistically significant association with all-cause dementia (HR = 1.20, 95% CI: 0.91-1.59) or AD (HR = 1.18, 95% CI: 0.91-1.54).
Why it matters
This review synthesizes prospective observational data indicating that long sleep duration, rather than short sleep duration, is a significant predictor of future dementia and Alzheimer's disease risk.
Limits
The total number of participants is not reported in the abstract. Only a modest number of cohorts were identified (6 to 7 studies), and observational designs cannot rule out residual confounding or reverse causation, such as long sleep being an early prodrome of neurodegeneration.
Cited by
- contradicts Short sleep duration predicts all-cause mortality and is a significant lifestyle factor determining the risk of developing Alzheimer's disease.