Sleep Duration and Cognition in a Nationally Representative Sample of U.S. Older Adults.

Objective: Excessive and insufficient sleep have been associated with cognitive dysfunction in older adults in U.S. and non-U.S.

Studies: However, the U.S. studies were not in nationally representative samples. The authors investigated the association between sleep duration and cognitive performance in a nationally representative sample of U.S. older adults.

Participants: The authors studied 1,496 survey participants aged 60 years or older from the National Health and Nutrition Examination Survey 2013-2014 dataset.

Measurements: Our primary predictor was weekday (or workday) nighttime sleep duration, categorized as 2-4, 5, 6, 7 (reference), 8, 9, and 10 hours or more. The authors studied five cognitive outcomes: Consortium to Establish a Registry for Alzheimer's Disease Word Learning (CERAD-WL) immediate recall, CERAD-WL delayed recall, Animal Fluency Test (AFT), Digital Symbol Substitution Test (DSST), and subjective cognitive problems (SCP).

Results: After adjusting for age, sex, race, education, depressive symptoms, and sedative-hypnotic use, sleep duration of 10 hours or more was significantly associated with lower scores on CERAD-WL immediate recall, CERAD-WL delayed recall, AFT, and DSST, and greater odds of SCP; sleep duration of 8 hours or more was associated with lower CERAD-WL delayed recall scores: 8, 9, and 10 hours or more. After adjustment, there were no significant associations of shorter sleep duration with cognition.

Conclusion: In U.S. adults aged 60 years or older, long nighttime weekday or workday sleep duration is associated with poorer verbal memory, semantic fluency, working memory, and processing speed in addition to greater odds of self-reported cognitive problems. Long sleep duration may be a marker of fragmented sleep or neurodegeneration in U.S. older adults.