Does subjective sleep affect cognitive function in healthy elderly subjects? The Proof cohort

Objective: Some epidemiological data are available on the association between sleep duration and sleep quality, sleep complaints, and the aging related cognitive impairment in the elderly. In this study we examined a large sample of healthy elderly subjects to assess the relationship between sleep quality, subjective cognitive complaints, and neuropsychological performance. Methods: A total of 272 elderly subjects (mean age 74.8 +/- 1.1 years) were recruited from a population-based cross-sectional study on aging and cardiovascular morbidity. All subjects filled in self-assessment questionnaires evaluating cognitive function, anxiety, depression, sleep-related parameters, and the Pittsburgh Sleep Quality Index (PSQI). Ambulatory polygraphy and extensive neuropsychological tests were also performed. Based on the total PSQI score, subjects were classified as good sleepers (GS, PSQI < 5, n = 116) and poor sleepers (PS, PSQI >= 5, n = 156). Results: Poor sleep did not affect the subjective cognitive function score, subjective cognitive impairment being mainly related to anxiety, depression, and sleep medication intake. No significant differences were seen between GS and PS in any of the objective cognitive function tests except for the Trail Making Test A (TMA-A), processing speed being longer in the PS group (p < 0.001). Neither the presence of sleep-related breathing disorders nor gender affected cognitive performance. Conclusions: Our results suggest that in healthy elderly subjects, subjective sleep quality and duration did not significantly affect subjective and objective cognitive performances, except the attention level, for that the interference of sleep medication should be considered. (C) 2012 Elsevier B.V. All rights reserved.