Abstract
INTRODUCTION
Sleep and dementia are complex phenotypes shaped by genetic and environmental factors, but the genetic contribution of sleep to dementia risk remains unclear. This study examined associations of both phenotypic and genetically predicted sleep traits and their interaction with dementia risk.
METHODS
Data were drawn from the Screening Across the Lifespan Twin study (1998 to 2002) within the Swedish Twin Registry. Phenotypic sleep traits included sleep duration, insomnia, snoring, daytime sleepiness, chronotype, daytime napping, and a composite sleep score. Corresponding polygenic scores (PGSs) were derived from publicly available genome-wide association study summary statistics. Dementia diagnosis was obtained from national registers. Cox proportional hazards models estimated risk, excluding cases diagnosed within 10 years of baseline to reduce reverse causation.
RESULTS
Among 13,087 individuals (mean age 70.27; 1541 dementia diagnosis cases), longer sleep duration (hazard ratio [HR] 0.93; 95% confidence interval [CI]: 0.86 to 1.00; p = 0.04) was associated with lower dementia risk over 13.42 years in models adjusted for sociodemographic and lifestyle behavioral factors. In within-pair analyses, this association was attenuated. Among 16,164 genotyped individuals (mean age 55.32; 559 cases), a one-standard deviation higher PGS for daytime napping (HR 1.12; 95% CI: 1.01 to 1.23; p = 0.03) was associated with higher dementia risk over 16.01 years. In 3133 individuals with both data types (mean age 66.79 years; 377 cases), this association persisted independently of phenotypic napping (HR 1.17; 95% CI: 1.03 to 1.33; p = 0.02), with no interaction observed.
DISCUSSION
Genetic liability to daytime napping in midlife may reflect a distinct vulnerability for dementia, whereas napping in late-life may serve a compensatory or restorative function.
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This post is Copyright: | November 9, 2026
Neuro-Dementia