Duration and Quality of Sleep as Risk Factors for Cognitive Impairment: An Umbrella Review of Systematic Reviews.
Level 3 - non-randomized controlled study
Systematic review of systematic reviews of observational studies (umbrella review)
PubMed 41854212 · doi:10.1002/gps.70206
What was done
An umbrella review (PROSPERO CRD420250655199; PRISMA/PRIOR guidelines) searched PubMed, Ovid MEDLINE, PsycINFO, and Google Scholar through February 2025. It included peer-reviewed systematic reviews and meta-analyses of observational studies (cohort, cross-sectional, or case-control) evaluating sleep duration or sleep quality as exposures and irreversible cognitive decline or dementia as outcomes. Reviews focusing primarily on parasomnias or sleep apnea were excluded. Methodological quality was evaluated using the CASP tool, and evidence certainty was rated with GRADE.
What was found
From 786 records, 13 systematic reviews were included, 11 of which contained meta-analyses. Five reviews reported associations with long sleep duration, six with short sleep duration, and three found no significant association with short sleep duration. Among five cohort-based reviews, three supported an association between sleep duration and cognitive decline. Two of three low-bias reviews also supported this association. No low-risk or cohort-only reviews specifically examined sleep quality alone, though two reviews assessing both duration and quality reported increased dementia risk. Cohort-only and low-bias reviews supported a U-shaped association between sleep duration and cognitive impairment. The abstract reported no pooled numerical effect sizes.
Why it matters
Sleep duration is not currently included among modifiable dementia risk factors in the Lancet Commission reports. This umbrella review consolidates secondary evidence indicating that both short and long sleep duration are associated with cognitive decline in longitudinal cohorts.
Limits
The underlying evidence is observational and was rated as low certainty using GRADE. No low-risk or cohort-only reviews evaluated sleep quality independently of duration. The abstract lacks specific effect sizes, duration cutoff values, and total participant counts.
Cited by
- context Consistently sleeping fewer than 6 hours per night is associated with an increased risk of dementia.