Morning Naps Predictive of Alzheimer’s Dementia?

Elderly people who nap in the morning and not at other times of the day are twice more likely to develop dementia due to Alzheimers disease, according to a recent study published in the journal Sleep.

The study, which was also presented at SLEEP 2023, enrolled 1203 participants from the Rush Memory and Aging Project (MAP), with a mean age of 80 years; 77% of the selected subjects were female. They were followed up for a mean period of ~7 years for development of dementia due to Alzheimer’s disease. All the participants wore an accelerometer to measure activity. The nap times were categorized as morning (9-11am), noon (11am-1pm), early afternoon (1-3pm), late afternoon (3-5pm) and early evening (5-7pm).

During the follow-up period, 30% of the participants were diagnosed with Alzheimers dementia. The mean time to develop Alzheimer’s dementia was 6.34 years. Those who napped in the morning were 2-folds more at risk of Alzheimer’s dementia compared to those who took their naps at other times with a hazard ratio (HR) of 1.93. Women who napped between 9 and 11 am were at greater risk (HR 2.22) vs men (HR 1.01). However, this association was seen to diminish after adjusting for BMI, total duration and frequency of the naps, and intradaily variability in rhythms (HR 1.71). However, this association was not observed for naps at other times of the day; HR for naps during noon time was 1.02; for early afternoon, it was 1.28; for late afternoon and early evening, HR was 0.62.

The duration of naps in day time increases with advancing age. However, this study highlights the significance of nap time in the risk of dementia. Napping during the morning was associated with greater risk of dementia due to Alzheimer’s disease compared to napping later in the day. Whether restricting morning napping would reduce the risk of cognitive decline requires further studies.

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