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. 2017 Mar 21;88(12):1172-1179.
doi: 10.1212/WNL.0000000000003732. Epub 2017 Feb 22.

Prolonged Sleep Duration as a Marker of Early Neurodegeneration Predicting Incident Dementia

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Prolonged Sleep Duration as a Marker of Early Neurodegeneration Predicting Incident Dementia

Andrew J Westwood et al. Neurology. .
Free PMC article

Abstract

Objective: To evaluate the association between sleep duration and the risk of incident dementia and brain aging.

Methods: Self-reported total hours of sleep were examined in the Framingham Heart Study (n = 2,457, mean age 72 ± 6 years, 57% women) as a 3-level variable: <6 hours (short), 6-9 hours (reference), and >9 hours (long), and was related to the risk of incident dementia over 10 years, and cross-sectionally to total cerebral brain volume (TCBV) and cognitive performance.

Results: We observed 234 cases of all-cause dementia over 10 years of follow-up. In multivariable analyses, prolonged sleep duration was associated with an increased risk of incident dementia (hazard ratio [HR] 2.01; 95% confidence interval [CI] 1.24-3.26). These findings were driven by persons with baseline mild cognitive impairment (HR 2.83; 95% CI 1.06-7.55) and persons without a high school degree (HR 6.05; 95% CI 3.00-12.18). Transitioning to sleeping >9 hours over a mean period of 13 years before baseline was associated with an increased risk of all-cause dementia (HR 2.43; 95% CI 1.44-4.11) and clinical Alzheimer disease (HR 2.20; 95% CI 1.17-4.13). Relative to sleeping 6-9 hours, long sleep duration was also associated cross-sectionally with smaller TCBV (β ± SE, -1.08 ± 0.41 mean units of TCBV difference) and poorer executive function (β ± SE, -0.41 ± 0.13 SD units of Trail Making Test B minus A score difference).

Conclusions: Prolonged sleep duration may be a marker of early neurodegeneration and hence a useful clinical tool to identify those at a higher risk of progressing to clinical dementia within 10 years.

Figures

Figure 1
Figure 1. Overview of the study design
For the analysis of incident dementia, both the original and offspring study participants were studied together. Sleep was related to cross-sectional cognitive performance and brain MRI in the offspring cohort only. After exclusion of persons with missing covariates, the final analysis sample was 2,457 for analysis of incident dementia. Sample sizes depict data for sleep duration measured at baseline. AD = Alzheimer disease.
Figure 2
Figure 2. Cumulative incidence of dementia by total sleep time
Cumulative incidence of (A) all-cause dementia by hours of sleep in the whole sample, (B) Alzheimer disease (AD) dementia by hours of sleep in the whole sample, (C) all-cause dementia by hours of sleep in persons without a high school degree, (D) AD dementia by hours of sleep in persons without a high school degree. Blue lines denote ≤9 hours sleep and red lines denote >9 hours sleep. Incidence curves are adjusted for age, sex, and cohort.

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