Science

Andrew J. Westwood, MD; Alexa Beiser, PhD; Nikita Jain
Jayandra J. Himali, PhD; Charles DeCarli, MD; Sanford H. Auerbach, MD; Matthew P. Pase, PhD; Sudha Seshadri, MD

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 5 2,457, mean age 72 6 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 (b 6 SE, 21.08 6 0.41 mean units of TCBV difference) and poorer executive function (b 6 SE, 20.41 6 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.