Long and frequent naps might be an early sign of cognitive impairment and Alzheimer’s disease, according to a new study.
Although poor nighttime sleep has previously been linked to cognitive impairment, the new study shows how it relates to daytime sleep.
Starting in 2005 and spanning 14 years, more than 1,000 people with an average age of 81 received wrist-worn devices that recorded data regarding their movements. Absence of movement for a long period between 9 a.m. and 7 p.m. was recorded as a nap.
Each year, participants wore the device for up to 14 days and took tests of their cognitive abilities.
Daily nap time increased by an average of 11 minutes per year in people who did not develop cognitive impairment.
In contrast, daily naps increased by an average of 25 minutes per year in people who developed mild cognitive impairment, and increased to 68 minutes in participants who developed Alzheimer’s disease.
As people aged, they also naped more often, but the number of extra naps they took each year almost doubled in mild cognitive impairment, and was almost four times higher in Alzheimer’s disease.
The authors reported that participants who took a nap for more than an hour a day had a 40% higher risk of developing Alzheimer’s disease than those who took a nap for less than an hour. And those who nap once or more a day were also 40% more likely to develop Alzheimer’s disease than those who nap less than once a day.
The authors noted that the relationship appeared to go both ways, with increased naps being linked to increased cognitive impairment one year later, and increased cognitive impairment being linked to increased naps the following year. Next year.