Long Sleep and Insomnia are Associated with Reduced Global Cognitive Function across Diverse Populations
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Background
Although sleep disorders are generally associated with cognitive decline, definitions of sleep conditions and cognitive function vary greatly across studies. Therefore, we evaluated associations between consensus definitions of sleep and cognitive outcomes across multiple studies.
Methods
Consensus sleep measures were ascertained at baseline visits in three cohort studies (HCHS/SOL, MESA and ARIC, N=11,563): short and long sleep (≤6hours and ≥9hours), insomnia (Women’s Health Initiative Insomnia Rating Scale≥10 or ≥6 for 3 questions), daytime sleepiness (Epworth Sleepiness Scale≥11) and obstructive sleep apnea (OSA, Apnea-Hypopnea Index≥ 15). Cognitive measures were ascertained at baseline and follow-up visits in each study and used to calculate harmonized outcomes: global cognitive function (GCF) at baseline, change in GCF between baseline and follow-up, poor GCF at baseline (≥1SD below the median), and incident poor GCF at follow-up. Study-specific analyses were adjusted for age, sex, center, education, race/ethnicity, APOE4 and language of cognitive assessments as needed. Results were meta-analyzed across studies.
Results
Long sleep was consistently associated with lower baseline GCF (β=-0.19, SE=0.03, p=3.78x10 -14 , FDR p=7.56x10 -13 , p-heterogeneity=0.78) and increased odds of poor baseline GCF (OR=1.77, 95% CI=1.49-2.09, p=2.96x10 -11 , FDR p=2.96x10 -10 , p-heterogeneity=0.22) across cohorts. Insomnia was also suggestively associated with lower baseline GCF (β=-0.051, SE=0.02, p=0.01, FDR p=0.07, p-heterogeneity=0.005) and increased odds of poor baseline GCF (OR=1.22, 95% CI=1.06-1.41, p=6.76x10 -3 , FDR p=0.05, p-heterogeneity=0.03). Sleep measures were not associated with change in cognitive function.
Discussion
Associations of long sleep and insomnia with harmonized cross-sectional GCF across three large, multiethnic cohorts suggest that cognitive function may be associated with distinct sleep phenotypes.
