Sleep duration among US adults aged 60 years or older is associated with poorer verbal memory, semantic fluency, working memory, and processing speed, according to research published in the American Journal of Geriatric Psychiatry. In addition, long sleep duration may indicate fragmented sleep or neurodegeneration in older adults.

Because both excessive and insufficient sleep have been associated with cognitive dysfunction among older adults, researchers investigated the association between sleep duration and cognitive performance. Researchers used data from a nationally representative sample of 1496 adults aged ≥60 years (mean age, 69.3 years; 46.1% men) who completed the 2013 to 2014 National Health and Nutrition Examination Survey. The primary predictor was weekday (or workday) nighttime sleep duration. The 5 cognitive outcomes included Consortium to Establish a Registry for Alzheimer’s Disease Word Learning Immediate Recall and Delayed Recall; Animal Fluency Test; Digital Symbol Substitution Test; and subjective cognitive problems.

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After adjusting for age, sex, race, education, depressive symptoms, and sedative-hypnotic use, researchers found that sleep duration of ≥10 hours was significantly associated with poorer verbal memory, semantic fluency, working memory, and processing speed, as well as greater odds of self-reported cognitive problems. There were no significant associations of shorter sleep duration and cognition.

The study was limited by its reliance on self-reporting; its cross-sectional design, which precluded a longitudinal analysis; and the exclusion of institutionalized participants.

Researchers recommended that future studies examine both daytime and nighttime sleep in relation to cognitive performance and decline. Future studies will continue to add to our understanding of the connection between sleep duration and cognitive outcomes. “This knowledge could be used to inform public health policy, clinical guideline development, and both clinical assessment and practice,” researchers concluded.

Reference

Low VL, MN, Spira AP. Sleep duration and cognition in a nationally representative sample of U.S. older adults [published online July 4, 2019]. Am J Geriatr Psychiatry. doi:10.1016/j.jagp.2019.07.001