BY FRAN KRITZ
For people 65 and older, a daytime nap just after lunch and for at least an hour may be just the thing to preserve memory and cognition. That's according to a new study published online in the December 20, 2016 issue of the Journal of the American Geriatrics Society.
Previous studies found cognitive declines in some people 65 and older, as well as an increase in afternoon napping among some older people. Researchers at the Center for Sleep and Circadian Neurobiology at the University of Pennsylvania's Perelman School of Medicine and School of Nursing wondered if there was a relationship between the two, says Junxin Li, RN, PhD, the lead author of the study and a postdoctoral research fellow at the center.
Dr. Li says earlier studies showed that 22 to 69 percent of older adults take daytime naps, a much higher rate than younger people, and that in China a post-lunch nap is considered part of a healthy lifestyle.
Dr. Li and colleagues conducted telephone interviews with nearly 3,000 Chinese men and women age 65 and older enrolled in the ongoing China Health and Retirement Longitudinal Study, a multiyear study looking at health factors among 18,000 people in China and their spouses, ages 45 and older. The researchers conducted cognitive assessments, including measuring attention span and short-term memory, by asking participants to recite back a list of words.
Participants were also asked about medical conditions, whether they napped after lunch, and if yes, how long the naps lasted and how many hours they slept each night. Additional questions included where the participants lived, their health habits, and their social activities.
Study participants were categorized as non-nappers (0 minutes), short nappers (less than 30 minutes), moderate nappers (30–90 minutes), and extended nappers (more than 90 minutes). Among the participants, nearly 60 percent said they napped between 30 and 90 minutes each day, with an average of 63 minutes.
After accounting for differences in age, education, and general health, researchers found a correlation between naps and performances on cognitive assessments. Participants who took an hour nap after lunch did better on the cognitive tests compared to the people who did not nap or who took either shorter or longer naps. Significantly, people who took no naps, short naps, or longer naps had decreases in their mental ability that were four-to-six times greater than those who took one-hour naps. Those decreases in ability were about the same as would be expected for someone about five years older than each participants' actual age, according to the researchers.
Dr. Li calls the results "intriguing" but acknowledges that the results show an association between napping and cognitive ability rather than a causal effect. The team plans more studies to see if a causal relationship exists.
Dr. Li says that because their study was done among people age 65 and older, their findings are applicable only to people in that age range, though previous studies have shown that napping benefits cognition in other age groups. And while the new study did not examine the connection between napping and insomnia, Dr. Li says that "generally speaking, daytime naps are not recommended in patients with insomnia."
The study found that those who napped longer also slept longer, but those participants may have been "genetic long sleepers" (they both nap and sleep longer), says Dr. Li. "For some long sleepers, the quality of sleep may be poor and therefore they nap in the afternoon to compensate."
The Art of Napping
Based on the study, Dr. Li says the optimum nap should occur no later than 4 pm and for no more than 60 to 90 minutes. Otherwise, it will interfere with nighttime sleep, which has its own brain benefits. "Older adults should schedule an afternoon nap," he says, "rather than falling asleep while watching TV or continuous dozing, which can be interrupted."