Abstract: Objective · To analyze the effect of sleep duration on cognitive function of the elderly with normal cognitive function. Methods · A total of 572 elderly people with normal cognitive function (NC group), 224 patients with amnestic mild cognitive impairment (aMCI) and 48 patients with Alzheimers disease (AD) were selected as the subjects. A unified questionnaire was used to collect their general data including demographic information, daily life information and so on. At the baseline stage, the correlation between sleep duration and cognitive function of NC group, aMCI group and AD group were compared, respectively. The elderly in NC group were followed up for one year to confirm the change of their cognitive function and analyze the correlation between sleep duration and cognitive function. Results · In NC group, the sleep duration in adolescence was positively correlated with Mini-Mental State Examination (MMSE) score (r0.114, P0.006) and Montreal Cognitive Assessment (MoCA) score (r0.116, P0.006), while the sleep duration in old age was positively correlated with MMSE score (r0.124, P0.004). For 572 elderly people with normal cognition, 282 cases of one year follow-up data were available. Twenty-nine patients diagnosed as aMCI and 6 patients diagnosed as AD were classified into progressive (NC-P) group, while 224 normal elderly subjects and 5 successful elderly subjects were classified into s(NC-S) group. The average age (P0.000), female percentage (P0.003) and heart disease rate (P0.001) in NC-P group were higher than those in NC-S group, while the number of years of education (P0.000), sleep duration in old age (P0.001) and the smoking history rate (P0.040) in NC-P group were lower than those in NC-S group, and the differences were statistically significant. Logistic multivariate regression analysis showed that decreased sleep duration (P0.001) and heart disease (P0.003) were the main risk factors for cognitive impairment in normal elderly people within one year. Conclusion · There is a positive correlation between cognitive function level and sleep duration in the elderly with normal cognition. Reduced sleep duration in the elderly is a risk factor for aMCI.

Key words: sleep duration, cognitive function, amnestic mild cognitive impairment, risk factor