Beijing: A regular afternoon nap can keep your brain sharp as a new study suggests that afternoon napping is linked to better mental agility.

The researchers, including Wei Li from the Shanghai Jiao Tong University in China, suggest that afternoon nap seems to be associated with better locational awareness, verbal fluency and working memory.

For the study, published in the journal General Psychiatry, the researchers involved 2,214 ostensibly healthy people aged at least 60 and residents of several large cities around China.

In all, 1,534 took a regular afternoon nap, while 680 did not. 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 visuospatial 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 did not nap.

And there were significant differences in locational awareness, verbal fluency, and memory.

This is an observational study, and so can't establish the cause. And there was no information on the duration or timing of the naps taken, which may be important, the researchers said.

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.

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