The benefits of napping are well known, however a new study led by Chinese researchers at the Sleep Center at John Hopkins University, Baltimore (USA), has re-established these benefits while providing further details on the ideal length of time for a nap. To really experience the cognitive benefits of napping, nap time should be neither too long nor too short. So, what is the ideal length of time?

In this study, a team of researchers, led by Professor Junxin Li, questioned 2,974 Chinese people aged 65 years and over. Each person was asked (amongst other things) if they were used to taking an afternoon nap, and if so the average length of time. Then according to napping duration, individuals were classified into four groups: non-nappers (0 minutes), short nappers (<30 minutes), moderate nappers (30–90 minutes), and extended nappers (>90 minutes). Finally, they were asked to perform a series of tests to evaluate their orientation, attention, episodic memory and visuospatial abilities.

The results, published in the Journal of the American Geriatrics Society, show that in comparison to the non-nappers, the moderate nappers (30-90 minutes) had the best results on the cognitive tests. The moderate nappers also had the best results in relation to the short nappers and extended nappers. Indeed, 57% of participants who said that they had a short daily afternoon nap of approximately one hour had results which were six times greater than their counterparts. According to Professor Junxin Li “Those who didn’t have an hour-long nap experienced a decline in cognition associated with a 5-year increase in age.”

This study indicates that naps should last exactly one hour; this appears to be the ideal length of time to protect memory and reasoning capacities. However, it is not so much the length of time of an afternoon nap (or nocturnal sleep) but its quality which is paramount, with a phase of light sleep, followed by deep sleep and finally REM sleep.