Accumulating evidence suggests that excessive daytime napping and Alzheimer’s disease may possess a bidirectional relationship or share common pathophysiological mechanisms.

Collaborating with the Rush Memory and Aging Project (MAP), we previously studied daytime napping duration and frequency objectively derived from actigraphy. We implemented the Cole-Kripke algorithm for sleep detection from actigraphy, which has been proved to work better especially in detecting daytime sleep than the Actiware approach. We modeled how baseline daytime napping characteristics were associated with future risk of dementia. We also modeled how daytime napping characteristics changed over time with individuals as they became even older. We found that 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.

Without our unique design of annual assessments of actigraphy and cognitive performance, we were also able to model the cross-lagged relationship between daytime napping characteristics and cognitive performance.

From the cross-lagged model, we observed that there were significant bidirectional cross-lagged associations between nap duration and global cognition, as well as between nap frequency and global cognition. Specifically, worse global cognition was correlated with longer nap duration/ increased nap frequency in the following year, and similarly, longer nap duration/ increased nap frequency was correlated with worse global cognition in the subsequent year.

References

However, previous research also suggest conflicting results, implying that the link can be more complicated. It is increasingly recognized that sleep and nap behaviors are inherently complex, and therefore, the relationship between napping and Alzheimer’s disease is likely multifaceted. A multi-dimensional approach should be implemented for the assessment of nap behaviors.

Timing and irregularity of daytime napping and Alzheimer’s disease

• Sponsored by:
• Project period: 2022-2025

We will study the relationship between timing and regularity of daytime napping, cognitive functioning, and development of Alzheimer’s. We will examine 1,400 older adults in the MAP and objectively measure sleep/wake states using wristband actigraphy, a non-invasive method of recording human sleep-wake cycles, and identify daytime napping schedule and duration. In addition, We will also study whether the timing and consistency of daytime naps interact with specific genetic risk factors for Alzheimer’s to influence the trajectory of cognitive changes over time.

Daytime napping and Alzheimer’s disease in middle-to-older aged adults: Timing, irregularity, and interaction with genetic risks

• Sponsored by:
• Project period: 2023

In middle-to-older aged adults, the relationship between Alzheimer’s disease and daytime sleep or nap is yet to be better understood. This project will test whether actigraphy-measured napping is cross-sectionally associated with cognition and prospectively associated with incident dementia/AD in a sample of ~99,000 participants. Findings will improve the understanding of risk factors for cognitive impairments in the aging population and help identify people at elevated risks of dementia at early stages (e.g., shift-workers with frequent and irregular naps).