You'll have to ask your doctor what should be the length of your daytime naps so you can set the timer appropriately.
Daytime napping and Alzheimer's dementia: A potential bidirectional relationship
Peng Li and Lei Gao contributed equally.
Kun Hu and Yue Leng share co-senior authorship.
Abstract
Introduction
Daytime napping is frequently seen in older adults. The longitudinal relationship between daytime napping and cognitive aging is unknown.
Methods
Using data from 1401 participants of the Rush Memory and Aging Project, we examined the longitudinal change of daytime napping inferred objectively by actigraphy, and the association with incident Alzheimer's dementia during up to 14-year follow-up.
Results
Older adults tended to nap longer and more frequently with aging, while the progression of Alzheimer's dementia accelerates this change by more than doubling the annual increases in nap duration/frequency. Longer and more frequent daytime naps were associated with higher risk of Alzheimer's dementia. Interestingly, more excessive (longer or more frequent) daytime napping was correlated with worse cognition a year later, and conversely, worse cognition was correlated with more excessive naps a year later.
Discussion
Excessive daytime napping and Alzheimer's dementia may possess a bidirectional relationship or share common pathophysiological mechanisms.
1 BACKGROUND
Excessive daytime napping is frequently seen in older adults, especially in those with Alzheimer's disease (AD).1 A recently proposed mechanism is the arousal deficiency due to neuronal and neurotransmitter loss in wake-promoting neurons associated with tau tangles,2 one of the pathological hallmarks of AD, resulting in sleep-wake disturbances and a higher propensity for daytime napping. The other way around, excessive sleepiness during daytime, which may be a cause of longer and frequent naps, has also been linked to faster cognitive decline or AD pathology build-up.3-5
However, there remains conflicting results regarding the effects of daytime napping on cognition in prior research. While some research has shown benefits of napping on acute cognitive performance, mood, and alertness, particularly in younger adults,6, 7 more naps have also been tied to adverse outcomes in long term, including poor cognition.8-11 For example, some cross-sectional studies reported associations between excessive self-reported napping and worse cognitive function;12-15 a recent longitudinal study also showed an association between longer nap duration and faster cognitive decline in older men.1 However, others also demonstrated the opposite way—self-reported napping was associated with lower odds of having cognitive impairment.16
Nevertheless, all prior studies have performed only one single nap assessment for each participant. It remains unclear how daytime napping evolves with aging, particularly cognitive aging. In addition, these studies mostly used subjective nap assessments that may not be reliable, especially in older adults given their cognitive status.17 Longitudinal assessments of objective naps are required to understand the complex link between daytime napping and AD.
In the current work, we primarily tested two hypotheses: (1) participants nap longer and/or more frequently with aging, and this longitudinal change is exacerbated as participants progress from no cognitive impairment to mild cognitive impairment (MCI), and is further accelerated after the diagnosis of Alzheimer's dementia; and (2) participants with excessive objective daytime napping (i.e., longer and/or more frequent) are at increased risk of developing Alzheimer's dementia. Meanwhile, we also tested how daytime napping and cognitive performance drive each other's change longitudinally using bivariate cross-lagged modeling. Testing these hypotheses will help clarify the relationship between daytime napping and Alzheimer's dementia by unraveling how the evolution of napping is intertwined with cognitive aging or the progression of Alzheimer's dementia.
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