Sleep patterns change with aging, independent of other factors, and include advanced sleep timing, shortened nocturnal sleep duration, increased frequency of daytime naps, increased number of nocturnal awakenings and time spent awake during the night, and decreased slow wave sleep. Most of these changes seem to occur between young and middle adulthood; sleep parameters remain largely unchanged among healthy older adults. The circadian system and sleep homeostatic mechanisms become less robust with normal aging. The amount and pattern of sleep-related hormone secretion change as well. The causes of sleep disturbances in older adults are multifactorial.

OBJECTIVES: To examine the cross-sectional associations between self-reported postlunch napping and structured cognitive assessments in Chinese older adults. DESIGN: Cross-sectional cohort study. SETTING: China. PARTICIPANTS: Individuals aged 65 and older from the baseline national wave of the China Health and Retirement Longitudinal Study (CHARLS) (N = 2,974). MEASUREMENTS: Interview-based cognitive assessments of orientation and attention, episodic memory, visuospatial abilities, and a combined global cognition score incorporating these assessments. Other self-reported or interviewbased assessments included postlunch napping duration, nighttime sleep duration, demographic characteristics, health habits, comorbidities, functional status and social activities. According to reported napping duration, older adults were categorized as non-nappers (0 minutes), short nappers (<30 minutes), moderate nappers (30-90 minutes), and extended nappers (>90 minutes). RESULTS: Postlunch napping was reporting in 57.7% of participants for a mean of 63 minutes. Cognitive function was significantly associated with napping (P < .001). Between-group comparisons showed that moderate nappers had better overall cognition than nonnappers (P < .001) or extended nappers (P = .01). Nonnappers also had significantly poorer cognition than short nappers (P = .03). In multiple regression analysis, moderate napping was significantly associated with better cognition than non-(P = .004), short (P = .04), and extended napping (P = .002), after controlling for demographic characteristics, body mass index, depression, instrumental activities of daily living, social activities, and nighttime sleep duration. CONCLUSION: A cross-sectional association was found between moderate postlunch napping and better cognition in Chinese older adults. The cross-sectional design and selfreported measures of sleep limited the findings. Longitudinal studies with objective napping measures are needed to further test this hypothesis. J Am Geriatr Soc 65:373-380, 2017.

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