Researchers suggest that an afternoon nap of around 1 hour may boost cognitive functioning in older adults.
Study co-author Junxin Li, Ph.D., of the Center for Sleep and Circadian Neurobiology at Johns Hopkins University in Baltimore, MD, and team report their findings in the Journal of the American Geriatrics Society.
As we age, our cognitive functioning declines; we might have problems remembering names, forget where we left our keys, or have trouble learning new information.
Studies have shown that being active, both mentally and physically, can help to keep the mind sharp in older age - but how about a good afternoon nap?
Napping and cognitive function
According to the National Sleep Foundation, an afternoon nap of around 20-30 minutes is best for boosting alertness and mental performance, without interfering with nighttime sleep.
The new study, however, suggests that an afternoon nap of around 1 hour is ideal for improving cognitive functioning among older adults.
Li and colleagues came to their findings by analyzing the data of 2,974 Chinese adults aged 65 and older who were part of the China Health and Retirement Longitudinal Study.
All participants underwent a series of tests that assessed attention, episodic memory, and visuospatial abilities, including mathematical tests, world recall, and figure drawing.
Subjects were also asked how long they napped for after lunch on each day during the past month, and they were categorized into four groups based on their answers. These categories were non-nappers (0 minutes), short nappers (less than 30 minutes), moderate nappers (30-90 minutes), and extended nappers (more than 90 minutes).
Better mental abilities for moderate nappers
The team reports that around 57.7 percent of participants reported engaging in post-lunch napping, with the average nap lasting for around 1 hour.
Compared with non-nappers, the researchers found that participants who had a moderate afternoon nap performed better in the cognitive tests.
Moderate nappers also had better cognitive performance than short nappers and extended nappers. On average, reductions in mental abilities of non-nappers, short nappers, and extended nappers were around four to six times greater than those of moderate nappers.
The team notes that subjects who took no naps, short naps, or extended naps experienced a decline in cognitive function that is comparable to a 5-year increase in age.
The researchers stress that their study is observational, so they cannot prove that afternoon naps directly benefit cognitive functioning among older adults.
Still, Li and colleagues believe that their results warrant further investigation:
"The results support the hypothesis that a moderate-duration nap taken during the post-lunch dip is associated with better overall cognition. Older adults who did not nap or napped longer than 90 minutes (extended nappers) were significantly more likely than those who napped for 30-90 minutes after lunch (moderate nappers) to have lower overall cognition scores after adjusting for possible confounders.
[...] The cross-sectional design and self-reported measures of sleep limited the findings. Longitudinal studies with objective napping measures are needed to further test this hypothesis."