Taking a regular afternoon nap may be linked to better mental agility, suggests researchers at The Fourth People's Hospital of Wuhu, Shanghai Mental Health Centre and Shanghai Jiao Tong University. It seems to be associated with better locational awareness, verbal fluency, and working memory, the findings indicate.
Longer life expectancy and the associated neurodegenerative changes that accompany it, raise the prospect of dementia, with around 1 in 10 people over the age of 65 affected in the developed world.
As people age, their sleep patterns change, with afternoon naps becoming more frequent. But research published to date hasn't reached any consensus on whether afternoon naps might help to stave off cognitive decline and dementia in older people or whether they might be a symptom of dementia.
The researchers explored this further in 2214 ostensibly healthy people aged at least 60 and resident in several large cities around China, including Beijing, Shanghai, and Xian. In all, 1,534 took a regular afternoon nap, while 680 didn't. All participants underwent a series of health checks and cognitive assessments, including the Mini Mental State Exam (MMSE) to check for dementia.
The average length of night time sleep was around 6.5 hours in both groups.
Afternoon naps were defined as periods of at least five consecutive minutes of sleep, but no more than 2 hours, and taken after lunch. Participants were asked how often they napped during the week; this ranged from once a week to every day.
The dementia screening tests included 30 items that measured several aspects of cognitive ability, and higher function, including visuo-spatial skills, working memory, attention span, problem solving, locational awareness and verbal fluency.
The MMSE cognitive performance scores were significantly higher among the nappers than they were among those who didn't nap. And there were significant differences in locational awareness, verbal fluency, and memory.
This is an observational study, and so can't establish cause. And there was no information on the duration or timing of the naps taken, which may be important.
But there are some possible explanations for the observations found, say the researchers.
One theory is that inflammation is a mediator between mid-day naps and poor health outcomes; inflammatory chemicals have an important role in sleep disorders, note the researchers.
Sleep regulates the body's immune response and napping is thought to be an evolved response to inflammation; people with higher levels of inflammation also nap more often, explain the researchers.
Relationship between afternoon napping and cognitive function in the ageing Chinese population
Han Cai, Ning Su, Wei Li, Xia Li, Shifu Xiao, Lin Sun
Published in General Psychiatry in January 2021
Several studies have shown that afternoon napping promotes cognitive function in the elderly; on the other hand, some studies have shown opposite results. This current study further examined the relationship between afternoon napping and cognitive function in the ageing Chinese population.
A total of 2214 elderly were included (napping group: n=1534; non-napping group: n=680). They all received cognitive evaluations by the Beijing version of the Montreal Cognitive Assessment, the Mini-Mental State Examination, and the Chinese version of the Neuropsychological Test Battery. Among all the subjects, 739 elderly volunteered to take blood lipid tests.
Significant differences in cognitive function and blood lipids were observed between the napping and the non-napping groups. Afternoon napping was associated with better cognitive function including orientation, language, and memory in the present study. Subjects with the habit of afternoon napping also showed a higher level of triglyceride than the non-napping subjects.
The results demonstrated that afternoon napping was related to better cognitive function in the Chinese ageing population.
General Psychiatry study (Open access)
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