Boston medical researchers in a new groundbreaking study have discovered a “vicious cycle” between daytime napping and Alzheimer’s dementia.
The Brigham and Women’s Hospital researchers found a link between the two: Excessive daytime napping predicted an increased future risk of Alzheimer’s dementia, and a diagnosis of Alzheimer’s dementia sped up the increase in daytime napping during aging.
Daytime napping is common among older adults, but researchers have not known the relationship between daytime napping and cognitive aging.
“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,” said Peng Li, of the Medical Biodynamics Program in the Brigham’s Division of Sleep and Circadian Disorders.
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There have been conflicting results about the effects of daytime napping on cognition in older adults. Some studies have shown that daytime napping has benefits on acute cognitive performance, mood and alertness, while other studies have highlighted the adverse outcomes on cognitive performance.
The current study tested two hypotheses: Participants nap longer and/or more frequently with aging and the changes are even faster with the progression of Alzheimer’s dementia; and participants with excessive daytime napping are at an increased risk of developing Alzheimer’s dementia.
In the new study, more than 1,000 people with an average age of 81 were provided Actical — a watch-like device to wear on their non-dominant wrist for up to 14 days. The team was able to identify sleep episodes through those devices.
The researchers learned that nap duration and nap frequency correlated with age, and found a relationship between daytime sleep and Alzheimer’s dementia. Longer and more frequent daytime naps were a risk factor for developing Alzheimer’s dementia in cognitively normal older men and women, the researchers discovered. Also, annual increases in napping duration and frequency were accelerated as the disease progressed.
The authors of the study called the relationship between daytime napping and cognition to be a “vicious cycle.”
“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 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.