The results, published in the journal Sleep Health, showed a 15 cubic centimetre difference - equivalent to 2.6 to 6.5 years of ageing. Total brain volumes were about 1,480 cubic centimetres in the study.
Previous research has shown that napping has cognitive benefits, with people who have had a short nap performing better in cognitive tests in the hours afterwards than counterparts who did not nap.
Using a technique called Mendelian randomisation, they looked at 97 snippets of DNA thought to determine people’s likelihood of habitual napping. They compared measures of brain health and cognition of people who are more genetically “programmed” to nap with counterparts who did not have these genetic variants, using data from 378,932 people from the UK Biobank study, and found that, overall, people predetermined to nap had a larger total brain volume.
The research team estimated that the average difference in brain volume between people programmed to be habitual nappers and those who were not was equivalent to 2.6 to 6.5 years of ageing.
But the researchers did not find a difference in how well those programmed to be habitual nappers performed on three other measures of brain health and cognitive function – hippocampal volume, reaction time and visual processing.
Lead author and PhD candidate Valentina Paz (University of the Republic (Uruguay) and MRC Unit for Lifelong Health & Ageing at UCL) said: “This is the first study to attempt to untangle the causal relationship between habitual daytime napping and cognitive and structural brain outcomes. By looking at genes set at birth, Mendelian randomisation avoids confounding factors occurring throughout life that may influence associations between napping and health outcomes. Our study points to a causal link between habitual napping and larger total brain volume.”
While the researchers did not have information on nap duration, earlier studies suggest that naps of 30 minutes or less provide the best short-term cognitive benefits, and napping earlier in the day is less likely to disrupt night-time sleep.
Fortunately, since I have been on rapamycin I am never sleepy in the daytime. Before I started rapamycin I frequently took afternoon naps because I was sleepy in the afternoons. Rapamycin has improved the quality and duration of my sleep time. So, I think that getting a good night’s sleep has been responsible for my lack of daytime sleepiness. I couldn’t take an afternoon nap now because I wouldn’t fall asleep.
I sleep on the average for 7.5 hours at night, but usually take 1-2 hour naps from 2 to 4 pm. It energizes me much for the rest of the day. Glad it positively affects brain.
I learn a lot on this board. This week’s take away is “take naps and eat chocolate.”
The optimal nap time seems to be less than an hour.
In conclusion, a longer nap was associated with a significantly elevated risk of CVD and all-cause mortality. Dose-response meta-analysis identified a J-curve dose-response relation between nap time and CVD risk, while there was a positive linear relation between nap time and all-cause mortality.
The Mediterranean Study says a total of 8.5 hours combined (nightime sleep and nap time) is best.
As reported here, midday napping was independently associated with higher levels of successful aging, whereas 8.5 h of sleep per day in total, not necessarily slept all together, seems to be the optimal duration for achieving the best successful aging level.
One can also try the Salvador Dali/Albert Einstein nap.
Salvador Dalí, in his 50 Secrets of Magic Craftsmanship for aspiring painters, outlined tips for the one-second micro-nap, including sitting upright, key in hand and upturned plate beneath. Once asleep, the key will drop and the ensuing clang ensures instant revival. Albert Einstein deployed a similar technique, using a spoon or pencil instead of a key.