Study objectives: To examine in cognitively intact older men and women the associations between subjective sleep quality and 1-yr incident cognitive impairment.
Design: Prospective cohort study.
Setting: General community.
Participants: 1,664 cognitively intact individuals age 65 to 96 years.
Measurements and results: Sleep quality at baseline was measured using the Pittsburgh Sleep Quality Index (PSQI). Cognitive functioning was assessed at baseline and 12 months later using the Mini-Mental State Examination (MMSE). Incident general cognitive impairment was defined according to a follow-up MMSE score below the 15(th) percentile according to normative data and of at least 2 points below baseline. General cognitive impairments were also separated into amnestic and nonamnestic subtypes according to MMSE delayed recall performance. Associations between sleep quality indicators at baseline and incident cognitive impairment were assessed by odds ratio (OR) adjusted for age, education, baseline MMSE score, psychotropic drug use, anxiety, depressive episodes, cardiovascular conditions, and chronic diseases. Results revealed that global PSQI score was significantly linked with incident cognitive impairment (OR 1.17, 95% confidence interval (CI) 1.05-1.30) in men, but not in women. In women, sleep disturbance score (OR 2.62, 95% CI 1.41-4.86) and long sleep duration (≥ 9 hr; OR 3.70, 95% CI 1.49-9.17) were associated with nonamnestic and amnestic incident cognitive impairment, respectively. In men, short sleep duration (≤ 5 hr; OR 4.95, 95% CI 1.72-14.27) and habitual sleep efficiency score (OR 1.94, 95% CI 1.42-2.66) were associated with amnestic and general incident cognitive impairment, respectively.
Conclusions: Sleep quality in older adults should receive particular attention by clinicians because poor sleep quality can be an early sign of cognitive decline.
Keywords: Sleep quality; cognition; cognitive decline; elderly.