Purpose: The authors examined the individual association between sleep quality and cognitive function among the very elderly.
Methods: The present study analyzed data from a survey that was conducted on all residents aged 90 years or older in a district; there were 2,311,709 inhabitants in 2005. Cognitive function and sleep quality were measured using the 30-item Mini-Mental State Examination and the Pittsburgh Sleep Quality Index, respectively.
Results: The subjects included in the statistical analysis were 216 men and 444 women. Subjects with poor sleep quality had significant lower cognitive function scores (P = 0.007) and higher prevalence of cognitive impairment (P = 0.035). Subjects with cognitive impairment had longer sleep latency (P < 0.0001) and lower sleep efficiency percentage (P = 0.006) and more likely reported with poor quality (P = 0.035). Multiple logistic regressions showed that poor sleep quality was a risk factor for cognitive impairment (unadjusted odds ratio, 1.719; 95% confidence interval, 1.138-2.597; adjusted odds ratio, 1.759; 95% confidence interval, 1.012-3.057).
Conclusions: Among longevity Chinese, there is an association between sleep quality and cognitive function, and cognitive impairment is associated with poor quality, longer sleep latency, and lower sleep efficiency percentage.