Long and frequent daytime napping in older adults may foreshadow the development of Alzheimer’s disease.

A recent study has found that older adults who nap throughout the day may be more likely to develop Alzheimer’s disease; and napping may also be characteristic of advancing Alzheimer’s disease, according to the study.

The study involved more than 1,400 older adults with an average age of 81. The participants wore a watch-type activity monitor for two weeks every year. Any prolonged period of no activity from the hours of 9 a.m. to 7 p.m. was categorized as a nap. Researchers also performed a battery of neurological tests each year.

At the outset of the study more than 75% of participants showed no signs of any cognitive impairment; 19.5% had mild cognitive impairment; and slightly more than 4% had Alzheimer’s disease. During approximately 14 years of follow-up, daily napping increased by about 11 minutes per year among participants who developed no cognitive impairment. The greater the increase in naps, the more quickly memory and thinking skills declined, according to study findings.

After a diagnosis of mild cognitive impairment, the rate of increase in naps doubled, and the rate of increase in naps nearly tripled after a diagnosis of Alzheimer’s disease, according to the study findings published in the journal Alzheimer’s & Dementia.

“Daytime napping and Alzheimer’s disease seem to be driving each other’s changes in a bi-directional way,” said study author Yue Leng, MD, PhD, an assistant professor of psychiatry at the University of California, San Francisco. “Older adults, and especially those with Alzheimer’s disease, should pay more attention to their daytime napping behaviors,” she said.

Leng noted that there are several possible ways in which daytime napping and Alzheimer’s disease may be linked. “It could be a reflection of underlying Alzheimer’s pathology at the preclinical stage that affects the wake-promoting network and contributes to increased daytime sleepiness,” she said. “Excessive daytime napping might also impact and interact with nighttime sleep, resulting in altered 24-hour circadian rhythms, which has also been linked to an increased risk of Alzheimer’s.”

Another aspect of the study sought to determine whether napping is actually a risk for developing Alzheimer’s disease. In an attempt to clarify this issue, the researchers compared participants who had normal memory and thinking skills at the start of the study but developed Alzheimer’s disease with their counterparts whose thinking remained stable over the course of the study. The researchers found that older individuals who napped more than one hour per day had a 40% higher risk of developing Alzheimer’s disease.

As suggested by study author Aron Buchman, MD, a professor of neurology at Rush University Medical Center and a neurologist at Rush Alzheimer’s Disease Center in Chicago, Alzheimer’s disease affects more than just memory and thinking skills. In some people, Alzheimer’s disease may steal memories but in others, it may result in sleep issues. In others, it could affect motor function, he explained.

“More studies are needed to better understand the relationship between napping and Alzheimer’s disease. But it’s possible that improving sleep may be a way of modifying the course of Alzheimer’s disease and its manifold manifestations,” Buchman said.