Is sleep quality a potential predictor of neurocognitive disorders? A 6-year follow-up study in Chinese older adults

Objective: To investigate the longitudinal association of sleep quality with incidence of neurocognitive disorders in 6 years. Methods: This was a 6-year follow-up study of community-living older adults who scored a Clinical Dementia Rating (CDR) of 0 at baseline. Sleep quality was assessed by the self-rated Pittsburgh Sleep Quality Index (PSQI) questionnaire, where higher scores indicated poorer sleep quality, and a cutoff score of 5 or above was suggestive of sleep disorder. The study outcome was incident neurocognitive disorders in 6 years, as identified by a CDR of 0.5 or above. Poisson regression analysis was conducted to test if baseline sleep quality was independently associated with risk of incident neurocognitive disorders in 6 years. Results: Of the 290 participants in this study, 166 (57.2%) developed neurocognitive disorders in 6 years. They had poorer sleep quality (mean [SD] total PSQI score: 6.2 [3.8] vs. 4.9 [3.2], p = 0.001) and higher prevalence of sleep disorder (100 [60.2%] vs. 56 [45.2%], p = 0.01) at baseline than those who remained free of neurocognitive disorder. After controlling for age, gender, education, and physical and psychiatric morbidities, the risk ratios (RRs) for incident neurocognitive disorders were 1.05 (95% confidence interval (CI) = 1.00-1.11, p < 0.05) for PSQI total score and 1.50 (95% CI = 1.05-2.14, p = 0.03) for sleep disorder at baseline. Conclusions: Sleep quality might predict the development of neurocognitive disorders. From a clinical perspective, enquiry of sleep quality and screening for sleep disorder should be promoted as part of the neurocognitive disorder risk assessment in older adults.