A new study found that daytime naps were associated with an increased risk of dementia.
Older adults in the study were 40 percent more likely to develop Alzheimer’s disease when they napped daily or snoozed for more than an hour on nap days, the study found. And, once they developed Alzheimer’s disease, the frequency and duration of naps increased.
“Daytime sleep behaviors of older adults are oftentimes ignored,” said the lead study author, Peng Li, PhD, of the division of sleep and circadian disorders at Brigham and Women’s Hospital in Boston, in an article in the Harvard Gazette.
“Our results not only suggest that excessive daytime napping may signal an elevated risk of Alzheimer’s dementia, but they also show that a faster yearly increase in daytime napping may be a sign of deteriorating or unfavored clinical progression of the disease,” Dr. Li said.
Each year of the study, the average duration of daytime naps increased by 11 minutes among the adults who didn’t develop cognitive problems. Scientists expected this because napping tends to become more common with age as a variety of issues — including more frequent awakenings for urination — disrupt sleep at night.
But the average duration of daytime naps increased twice as fast among participants who were diagnosed with mild cognitive impairment during the study, climbing by an average of 24 minutes per day.
And, daily naptime durations surged almost three times as fast among those who developed Alzheimer’s disease, rising by an average of 68 minutes.
The connection between dementia and excessive daytime napping persisted even after researchers accounted for the quality and quantity of sleep at night. Nighttime awakenings and variation in the amount or quality of sleep from one day to the next also didn’t influence the relationship between napping and dementia.
The study results were published in Alzheimer’s & Dementia on March 17.
One limitation of the study is that wrist-worn actigraphy isn’t the gold standard for measuring the quality or quantity of sleep. These devices track movement, and scientists assume that long stretches when people are motionless during the day indicate naps. It’s possible in some instances that people might be reading or watching television.
Beyond this, another drawback of the study is that the results from this elderly population, ranging in age from 74 to 88, might not reflect what would happen among younger adults.
Even so, the findings suggest that people need to pay closer attention to changes in their sleep habits as they age, especially if they feel like naps are becoming longer or more routine.
“Our study calls for closer attention to 24-hour sleep patterns — not only nighttime sleep but also daytime sleep — for health monitoring in older adults,” Li said.