Napping is in the genes and not a “behavioral choice,” a Harvard study has found.
Through examining the genomes of nearly half a million people from the UK, scientists discovered that daytime napping is “biologically driven”.
Researchers at Massachusetts General Hospital identified 123 regions in the human genome, which were associated with daytime napping.
Digging deeper into the data, they identified three potential napping mechanisms.
The first two, dubbed “disrupted sleep” and “early morning awakening” refer to people who nap because they either did not get enough sleep the night before or woke up at the crack of dawn.
The third referred to sleep propensity – how much sleep is required by a particular individual.
Dr Dashti said: “This tells us that daytime napping is biologically driven and not just an environmental or behavioural choice.”
Some of the genetic traits identified were also linked to health concerns, including obesity and high blood pressure, the researchers found.
Several of the napping gene variants were associated with orexin, a neuropeptide, linked to wakefulness.
The findings were published in the journal Nature Communications.
Co-author graduate student Iyas Daghlas at Harvard Medical School said: “This pathway is known to be involved in rare sleep disorders like narcolepsy, but our findings show that smaller perturbations in the pathway can explain why some people nap more than others.”
Scientists had analysed genetic information from 452,633 participants in the UK’s Biobank.
Participants were asked how often they napped during the day and given three choices – never/rarely, sometimes or usually.
Some were asked to wear an activity monitor, or accelerometers, to make sure they reported their snoozes accurately.
Dr Dashti added: “That gave an extra layer of confidence that what we found is real and not an artefact.”
A genome-wide association study (GWAS) was then carried out to identify genetic variations associated with napping.
This involved rapidly scanning complete sets of DNA, or genomes, for a large number of people.
Their findings were independently replicated by a consumer genetic-testing company called 23andMe who analysed the genomes of 541,333 people.
Co-author Dr Marta Garaulet at MGH said: “Future work may help to develop personalised recommendations for siesta.”
It comes after findings from the British Medical Journal that a five-minute nap in the afternoon can improve the memory and keep the brain more agile.
People who took regular afternoon naps appeared to speak more fluently and remember things better than those who did not break up the day with some sleep, according to the study.