Afternoon napping by older adults is tied to better memory and improved language skills, new research suggests.
A randomized study of more than 2000 elderly persons in China showed that those who engaged in afternoon napping that lasted less than 2 hours had significantly better scores on cognitive function measures than their counterparts who did not nap.
Total scores and orientation and language function scores on the Mini–Mental State Examination (MMSE) were significantly higher in the napping group, as were orientation scores on the Beijing version of the Montreal Cognitive Assessment (MoCA). Further tests also showed significant between-group differences in language fluency and digit span.
Interestingly, a subanalysis showed that among volunteers who underwent blood lipid testing, those who napped had higher triglyceride levels. There were no between-group differences in cholesterol, low-density lipoprotein (LDL), or high-density lipoprotein (HDL) levels.
Corresponding author Lin Sun, MD, Alzheimer’s Disease and Related Disorders Center and Department of Geriatric Psychiatry, Shanghai Mental Health Center, Shanghai, China, noted that napping appears to be very important for this population.
“This study found that a proper nap is beneficial to the maintenance of cognitive function, so we encourage the elderly to take a proper nap,” Sun, who is also from the School of Medicine at Shanghai Jiao Tong University, told Medscape Medical News.
The findings were published online January 25 in General Psychiatry.
Conflicting Findings
Previous studies that have examined napping and cognitive function have had conflicting results, with some showing positive outcomes and others suggesting the opposite. For the current study, the researchers sought to examine the association in a population where a “napping culture” is prevalent.
“Napping is very common in Chinese people, even a national feature; and the elderly have a higher frequency of napping,” Sun said. So, “we collected relevant information in a large flow survey, and the analysis results were interesting.”
The investigators analyzed data from a large national epidemiologic survey and included 2214 participants aged 55 years or older. Of these, 1534 (69.3%) reported that they were afternoon nappers. Napping was defined as participating in “periods of at least five consecutive minutes scored as sleep (inactivity) after lunch outside of the main sleep schedule.”
Participants also examined frequency and collected demographic data.
The researchers found no significant differences between the nappers and the non-nappers with respect to gender (58.4% men vs 59.7% women) and mean age (71 vs 70 years), years of education (7.37 vs 6.95), and hours of night sleep (6.54 vs 6.61 hours). There were also no significant between-group differences between participants who smoked, drank alcohol, or who had hypertension or diabetes.
Exclusion criteria included a history of mental illness or cognitive dysfunction, blindness, deafness, or any other major physical condition.
In addition to the MMSE and the Beijing version of the MoCA, all participants were assessed using the Chinese version of the Neuropsychological Test Battery (NTB). A subgroup of 739 volunteers also underwent blood lipid testing (nappers, n = 428).
Inflammatory Mediator?
Results showed that the napping group had a significantly higher mean total MMSE score than the non-napping group (25.3 vs 24.56; P = .003), as well as higher orientation (9.28 vs 9.01; P < .001) and language (7.27 vs 7.06; P = .02) scores on the MMSE.
In addition, the nappers had higher orientation scores on the MoCA (5.55 vs 5.41; P = .006) and higher digit span (3.24 vs 12.48; P = .009) and language fluency (24.35 vs 23.23; P = .02) scores on the NTB.
In the subgroup that underwent lipid testing, the nappers also showed higher levels of triglycerides than non-nappers (1.80 vs 1.75 mmol/L; P = .001).
“The results demonstrate that afternoon napping was related to better cognitive function in the Chinese ageing population,” the investigators write.
Regarding possible mechanisms that may be occurring, the researchers note that the “activity of inflammatory cytokines plays an important role in sleep disorders.”
Napping “is thought to be an evolved response to inflammation,” and those “with higher levels of inflammation also nap more frequently,” the investigators add.
Study limitations include its cross-sectional design and that it could not show direct causality.
No Definitive Answer ― Yet
Commenting for Medscape Medical News, Claire Sexton, DPhil, director of scientific programs and outreach for the Alzheimer’s Association, said that the study contributes to “what we understand about the relationship” between napping and cognitive function.
Dr Claire Sexton
“We know that sleep is important for cognitive health from a variety of different angles, but the role of naps is really still under debate,” said Sexton, who was not involved with the current research.
She noted that although this study showed that naps are beneficial, previous studies have linked naps with a worsening in cognitive decline down the line.
“This is an important study…but it has not brought us to the definitive answer and the definitive understanding just yet,” Sexton said.
She pointed out that the study did highlight some important factors that should be considered, including how naps are measured. She also noted that nap length may matter.
The current study limited naps to no more than 2 hours, whereas most previous studies included longer naps. “So it could be that these longer naps are what’s associated with worse cognitive impairment,” Sexton noted.
Another important point, she said, concerns the context of the nap. For example, a nap might be compensatory and beneficial if it happens after a poor night’s sleep. “But if you have a good night’s sleep and then you’re still needing to take long naps in the afternoon, that could be more of a warning sign,” Sexton added.
Asked whether the study findings are generalizable to a US population, Sexton noted that close to 70% of the participants reported taking some sort of nap, which may be high compared to other studies.
“The culture of napping varies from region to region, which can then limit how translatable the findings are. That’s why it’s so important that this type of research is done in different countries, so that we can gain a better understanding about what factors are common and what factors might be limited by regional factors,” said Sexton.
The study was funded by grants from the Shanghai Mental Health Center, the Shanghai Science and Technology Commission, the National Natural Science Foundation of China, and the Shanghai Jiao University School of Medicine. The study authors and Sexton have reported no relevant financial relationships.
Gen Psychiatry. Published online January 25, 2021. Full article
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