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Sleep. 2019 Apr 1;42(4). pii: zsz019. doi: 10.1093/sleep/zsz019.

Sleep and cognitive aging in the eighth decade of life.

Author information

1
Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK.
2
Department of Psychology, University of Edinburgh, Edinburgh, UK.
3
Division of Psychiatry, University of Edinburgh, Edinburgh, UK.
4
Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
5
Faculty of Medical and Health Sciences, University of East Anglia, Norwich, UK.
6
Alzheimer Scotland Dementia Research Centre, University of Edinburgh, Edinburgh, UK.
7
Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, UK.
8
Anne Rowling Regenerative Neurology Clinic, University of Edinburgh, Edinburgh, UK.
9
Usher Institute of Population Health Sciences and Informatics, University of Edinburgh, Edinburgh, UK.
10
Department of Sleep Medicine, Royal Infirmary of Edinburgh, Edinburgh, UK.
11
Centre for Genomic and Experimental Medicine, University of Edinburgh, Edinburgh, UK.

Abstract

We examined associations between self-reported sleep measures and cognitive level and change (age 70-76 years) in a longitudinal, same-year-of-birth cohort study (baseline N = 1091; longitudinal N = 664). We also leveraged GWAS summary data to ascertain whether polygenic scores (PGS) of chronotype and sleep duration related to self-reported sleep, and to cognitive level and change. Shorter sleep latency was associated with significantly higher levels of visuospatial ability, processing speed, and verbal memory (β ≥ |0.184|, SE ≤ 0.075, p ≤ 0.003). Longer daytime sleep duration was significantly associated slower processing speed (β = -0.085, SE = 0.027, p = 0.001), and with steeper 6-year decline in visuospatial reasoning (β = -0.009, SE = 0.003, p = 0.008), and processing speed (β = -0.009, SE = 0.002, p < 0.001). Only longitudinal associations between longer daytime sleeping and steeper cognitive declines survived correction for important health covariates and false discovery rate (FDR). PGS of chronotype and sleep duration were nominally associated with specific self-reported sleep characteristics for most SNP thresholds (standardized β range = |0.123 to 0.082|, p range = 0.003 to 0.046), but neither PGS predicted cognitive level or change following FDR. Daytime sleep duration is a potentially important correlate of cognitive decline in visuospatial reasoning and processing speed in older age, whereas cross-sectional associations are partially confounded by important health factors. A genetic propensity toward morningness and sleep duration were weakly, but consistently, related to self-reported sleep characteristics, and did not relate to cognitive level or change.

KEYWORDS:

cognitive aging; daytime sleep; polygenic scores

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