‘Vicious cycle’ discovered between too much daytime napping and Alzheimer’s disease

BOSTON, Mass. — Is a midday nap actually doing more harm than good for your brain? A new study has found a “vicious cycle” between older adults who nap during the day and their risk for Alzheimer’s disease.

Investigators at Brigham and Women’s Hospital say there’s a two-way relationship between napping and brain aging. Specifically, excessive daytime napping predicted an increase in the risk of Alzheimer’s onset later in life. At the same time, having Alzheimer’s led to an increase in daytime napping as patients got older.

“Daytime sleep behaviors of older adults are oftentimes ignored, and a consensus for daytime napping in clinical practice and health care is still lacking,” says Peng Li of the Medical Biodynamics Program in the Brigham’s Division of Sleep and Circadian Disorders, in a university release.

“Our results not only suggest that excessive daytime napping may signal an elevated risk of Alzheimer’s dementia, but they also show that faster yearly increase in daytime napping may be a sign of deteriorating or unfavored clinical progression of the disease. Our study calls for a closer attention to 24-hour sleep patterns — not only nighttime sleep but also daytime sleep — for health monitoring in older adults.”

Is napping good or bad?

Although sleep is an absolute necessity for human health, the benefits of napping during the day are not as clear. Although some studies have found that a short nap can boost both motor skills and memory, others have found that naps don’t make up for a lack of sleep at night and may even harm the heart if someone naps for more than an hour.

To find out how daytime sleeping impacts cognition in older adults, the Brigham team collaborated with researchers from the Rush Alzheimer’s Disease Center and the University of California-San Francisco. Using data from the on-going Rush Memory and Aging Project (MAP), the team studied over 1,000 adults with an average age of 81.

Each participant wore a watch-like device on their non-dominant wrist for two weeks. This allowed researchers to identify sleep episodes using a sleep scoring algorithm that measures physical activity. The team than calculated each person’s nap duration and frequency throughout the experiment.

Results show that nap duration and nap frequency have a clear connection to age. Moreover, the team confirmed that there is a two-way relationship between daytime sleep and the onset of Alzheimer’s — the most common form of dementia.

Study authors also found that napping increased among dementia patients as the disease progressed. This was especially true for older adults who were already displaying symptoms of the neurodegenerative condition.

“The vicious cycle we observed between daytime sleep and Alzheimer’s disease offers a basis for better understanding the role of sleep in the development and progression of Alzheimer’s disease in older adults,” Li says.

Increasing age may play a role

Researchers note their findings do have some limitations. One is that all of the participants were near or beyond the age of 80, meaning the results may not translate the same way to younger adults.

Additionally, study authors say they need to examine if intervening in someone’s daytime napping actually helps prevent the onset of cognitive decline.

“Our hope is to draw more attention to daytime sleep patterns and the importance of patients noting if their sleep schedule is changing over time,” concludes co-senior author Kun Hu of the Medical Biodynamics Program in the Brigham’s Division of Sleep and Circadian Disorders. “Sleep changes are critical in shaping the internal changes in the brain related to the circadian clocks, cognitive decline, and the risk of dementia.”

The findings are published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.