Association of sleep duration in middle and old age with incidence of dementia.
Level 3 - non-randomized controlled study
Prospective cohort study with long-term follow-up
PubMed 33879784 · doi:10.1038/s41467-021-22354-2
What was done
Researchers analyzed data from 7,959 participants in the Whitehall II cohort study followed for up to 25 years. They assessed whether sleep duration at ages 50, 60, and 70, as well as persistent short sleep across these ages, was associated with incident dementia (521 cases) compared to normal sleep duration (7 hours), adjusting for sociodemographic, behavioural, cardiometabolic, and mental health factors.
What was found
Compared to a 7-hour sleep duration, sleeping 6 hours or less was associated with higher dementia risk at age 50 (HR 1.22, 95% CI 1.01–1.48) and age 60 (HR 1.37, 95% CI 1.10–1.72), and was imprecisely estimated at age 70 (HR 1.24, 95% CI 0.98–1.57). Persistent short sleep duration at ages 50, 60, and 70 was associated with a 30% increased dementia risk compared with persistent normal sleep duration.
Why it matters
These findings suggest that short sleep duration during midlife is associated with an elevated risk of late-onset dementia independently of known confounders, indicating the link is present decades before typical clinical onset.
Limits
The abstract does not state whether sleep duration was objectively measured or self-reported. The Whitehall II cohort comprises British civil servants, which may limit generalizability. Observational design cannot rule out residual confounding or determine causation.
Cited by
- supports Consistently sleeping fewer than 6 hours per night is associated with an increased risk of dementia.