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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.
GLOSSARY
- AD=
- Alzheimer disease;
- CI=
- confidence interval;
- DSM-IV=
- Diagnostic and Statistical Manual of Mental Disorders, 4th edition;
- FHS=
- Framingham Heart Study;
- HR=
- hazard ratio;
- MCI=
- mild cognitive impairment;
- PAI=
- Physical Activity Index;
- TCBV=
- total cerebral brain volume
Footnotes
↵* These authors contributed equally to this work.
Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Supplemental data at Neurology.org
- Received March 17, 2016.
- Accepted in final form December 29, 2016.
- © 2017 American Academy of Neurology
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