A new study from researchers at Brigham and Women’s Hospital in Boston links excessive daytime napping by older adults to a heightened risk of developing Alzheimer’s, the disease that causes severe cognitive decline.
The study was published Thursday in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, the hospital said in a statement.
“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,” Dr. Peng Li, a lead author of the study who works in the Medical Biodynamics Program at the Brigham’s Division of Sleep and Circadian Disorders, said in the statement.
The researchers found not only that excessive daytime napping portended an increased risk of Alzheimer’s dementia, but also that an Alzheimer’s diagnosis “sped up the increase” in daytime napping during the aging process, the Brigham said.
“Daytime sleep behaviors of older adults are oftentimes ignored, and a consensus for daytime napping in clinical practice and health care is still lacking,” Li said. “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.”
Li said the 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.”
One medical expert not connected to the Brigham or the study said the findings appear to build upon existing research connecting sleep disorders and memory loss.
“There is a long-known interaction between, for example, sleep apnea and dementia,” Dr. Ina E. Djonlagic, a neurologist in Beth Israel Deaconess Medical Center’s Sleep Disorders Clinic, said in an interview Thursday.
It is unclear, though, whether changes in sleeping patterns affect memory and lead to dementia, or if the neurodegenerative process of dementia affects sleep in parallel, said Djonlagic, who is also an assistant professor at Harvard Medical School.
The study was based on participation by over 1,000 people, who had an average age of 81 years old, according to Brigham and Women’s Hospital.
Each participant received a watch-like Actical device to wear on their nondominant wrist for up to two weeks. Researchers, the statement said, identified sleep episodes with a scoring algorithm, and after napping episodes were identified, nap duration and frequency were tabulated.
While the use of Actical has been widely used in sleep field studies, the authors recognize that polysomnography is the “gold standard” for sleep scoring, the statement said.
Polysomnography, a National Institute of Health website says, involves testing participants’ body functions as they sleep, or try to sleep. When done in a health care setting, the site says, providers place electrodes on a participant’s “chin, scalp, and the outer edge” of their eyelids, with monitors recording heart rate and breathing.
The Brigham statement also noted the study’s participants were older, so the findings may not be “easily translated” to younger age groups. The hospital said future studies should test whether a direct intervention in daytime napping can lower the risk of Alzheimer’s dementia or cognitive decline.
Djonlagic cautioned that the Actical devices used in the study can sometimes misread resting as sleep.
“Actigraphy is not a great measure of sleep onset and what kind of sleep the person has,” she said. “You don’t know if they’re really napping.”
Djonlagic said she is concerned that the public could misinterpret the study’s findings, and start drinking coffee, instead of napping, when they tire during the day.
“I think the danger is always when you see these results in isolation,” she said. “The last thing you want people to think is, ‘I can’t nap, because if I nap I’m going to get dementia.’ That’s the message that you don’t want to give to people.”