Table 2

Qualitative syntheses for the relationship between sleep duration and cognitive disorders

OutcomeExposure levelDefinitionNSample size (case)Pooled resultsI2 (p value)P for publication bias
Dementia or cognitive declineHighest vs refNocturnal1353,014 (6,892)1.41 (1.17–1.70)69% (<0.01)0.4394
Lowest vs ref1.18 (1.01–1.37)57% (<0.01)0.1033
Highest vs refDaily46,925 (854)1.73 (1.30–2.31)9.6% (0.345)NA
Lowest vs ref1.83 (1.38–2.43)0% (0.563)NA
ADHighest vs refNocturnal332,555 (4,115)1.57 (1.33–1.85)0% (0.90)NA
Lowest vs ref1.02 (0.76–1.36)54% (0.11)NA
Highest vs refDaily24,783 (296)2.47 (1.55–3.93)0% (0.91)NA
Lowest vs ref2.27 (1.17–4.38)0% (0.89)NA
VDHighest vs refDaily24,783 (117)2.20 (1.12–4.32)0% (0.60)NA
Lowest vs ref2.33 (0.72–7.49)45% (0.18)NA
  • AD, Alzheimer’s disease; NA, not applicable.