SAN FRANCISCO — Reports of difficulty falling asleep were associated with poorer performance on some cognitive measures in a study of 174 elderly community-dwelling blacks.
Self-reported sleep trouble appears to be a unique predictor of cognitive performance, even after controlling for age, gender, education, depression, and current health, reported Alyssa A. Gamaldo of the psychology department at North Carolina State University, Raleigh, and her associates.
When asked whether they'd had any trouble falling asleep in the past year, 29% of participants said they did, a rate that's consistent with the findings of previous, more rigorous studies of sleep difficulties, she said at the annual meeting of the Gerontological Society of America. From 10% to 40% of older adults reported sleep difficulties in earlier studies.
Investigators in the current study analyzed data from a subset of blacks in the Baltimore Longitudinal Study of Aging. Participants were living independently and had a mean age of 73 years, a mean education of 10 years, and a mean monthly income of $800. The cohort was 71% women.
Those who reported sleep trouble tended to perform worse on measures of short-term memory and working memory. Short-term memory was measured by the forward digit span task and the backward digit span task, and working memory was measured by the alpha span task.
Participants also completed the Mini-Mental State Examination to measure global cognitive status and the California Verbal Learning Test to measure episodic memory, but results for these were not significantly different between adults who did or did not have trouble sleeping.
Several previous studies have suggested that the relationship between self-reported sleep difficulties and cognitive performance may be moderated by depression. In the current study, however, neither depression nor older age appeared to exacerbate differences in cognitive performance, Ms. Gamaldo said.
The study employed the Center for Epidemiological Studies Depression Scale to measure depressive symptoms and these scores were used to categorize 36 participants as depressed (a score of 16 or greater) and 138 as not depressed (score of 0–15).
The analysis did find one significant interaction related to age and depression. Participants who were both older and depressed were more likely to have low scores on the Mini-Mental State Examination.
To assess current health, participants were asked to rate their health on a scale from 1 (“very poor”) to 4 (“very good”).