Effects of napping on cognitive function modulation in elderly adults with a morning chronotype: A nationwide survey

Abstract

Circadian rhythms and napping habits have been associated with cognitive function; however, little is known about the interaction effects on cognitive function. The present study examined the moderating effects of napping habits on the relationship between chronotypes and cognitive function decline in elderly adults. This cross-sectional study analysed data from the 2009 Taiwan National Health Interview Survey. A total of 1,724 elderly adults (aged ≥65 years) were included. Cognitive function was determined by the Mini-Mental State Examination. Participants' chronotypes were assessed using the midpoint of sleep. Napping habits were assessed by self-report questions. Demographic data, health-related factors and sleep characteristics of the participants were also assessed as potential confounding factors. A hierarchical regression will be used to test the moderating role of napping habits in the relationship between chronotype and cognitive function level after adjustment for potential confounders. A significant interaction effect between chronotype and napping habits was observed with the MMSE score (b = -0.29, SE = 0.14, p = 0.03). Morning-type elderly patients with nap durations >60 min exhibited significantly higher MMSE scores than non-nappers (F = 7.48; p = 0.00). This nationwide survey confirms that in morning-type elderly adults, nap durations >60 min are associated with less cognitive decline; however, napping habits are not associated with cognitive function level in evening-type and intermediate-type elderly adults.

The Relationship between Chronotype, Physical Activity and the Estimated Risk of Dementia in Community-Dwelling Older Adults

“…However, the findings on the association between morning preference and a higher MMSE score in this study are not consistent with the results of research by Fang et al [20] where, without controlling for education, morning types were found to have significantly lower MMSE scores than evening types. They estimated the preference using actual habitual behavior patterns such as self-reported habitual mid-sleep timing on free days.…”

“…The association between the MEQ score and MMSE score were stronger in older adults aged 75 years and above. Previous studies have also shown significantly higher MMSE scores in morning types [20] than in evening types. Although the physiological mechanisms of the association between diurnal preference and the MMSE score is unclear, animal studies have shown the underlying mechanisms in the association between disrupted circadian rhythms and risk of AD.…”

“…Individuals have different chronotypes, and cognitive performances differ according to an individual's preferred chronotype (evening/morning) [19]. However in older adults, a study reported that different chronotypes show different levels of cognitive function, and the likelihood of cognitive impairment for the morning chronotype is low (after adjusting for education level) [20]. The studies are still not adequate to provide strong evidence regarding the relationship between chronotype and dementia.…”

Characteristics in the daily life of the elderly that indicate a risk of dementia

“…The PSQI scores were not significantly different between the 2 groups; however, the evidence 19,22) indicates that scheduled short naps (the Findings of our logistic regression suggested the possibility of dementia being associated with GDS and frequency of naps. These findings are supported by previous reports, 16,20,21) as was the GDS correlation with apathy score and vitality index. 25) Therefore, for early detection of dementia in elderly, we have to pay attention a tendency toward depression and ensure that they take adequate effective naps (≧ 3 times/week).…”

“…Although the number of daily activities differed from a previous report, 5) 69.9% 15) Napping is associated with less cognitive decline, 20) and benefits retention of episode memor y. 21) We hypothesize that our participants did not routinely take scheduled shor t naps, especially those in high risk group. The PSQI scores were not significantly different between the 2 groups; however, the evidence 19,22) indicates that scheduled short naps (the Findings of our logistic regression suggested the possibility of dementia being associated with GDS and frequency of naps.…”