Taking an hour's nap after lunch can keep your brain five years younger, according to a new study.But researchers found that a longer or shorter nap did not produce the same results.
The study involved around 3,000 Chinese adults over the age of 65 - with 60 per cent reporting that they had a nap after lunch ranging from 30 to 90 minutes.
Participants were given basic maths problems and memory tests to complete to assess their cognitive ability.
The research, published in Journal of the American Geriatrics Society, found that people who took an hour-long nap after lunch did better on the tests compared to the people who did not nap.
In fact, those who took shorter naps, longer naps or no naps at all showed decreases in their cognitive skills that were four to six times greater than those taking hour-long naps.
Dr Junxin Li, who led the research, said: 'These people also experienced about the same decline in their mental abilities that a five-year increase in age would be expected to cause.
'Cognitive function was significantly associated with napping. Comparisons showed that moderate nappers had better overall cognition than non-nappers or extended nappers.
'Non-nappers also had significantly poorer cognition than short nappers.'