Needing to ‘rest your eyes’ for a daytime snooze could be more than just exhaustion, according to a new study that found the need to nap may be in your DNA.
Researchers from the Massachusetts General Hospital (MGH) worked with data from the UK Biobank, which included genetic and general information on 452,633 people including whether they take a nap and how often.
There are 123 regions within the human genome linked to daytime napping and the authors say this shows that the need to nap is ‘biologically driven’ not environmental.
The regions linked to napping were more prominent in those volunteers who claimed to regularly take a nap during the day, the US team discovered.
Understanding the genetic markers for daytime napping could help doctors develop personalised recommendations for when to sleep, says study author Iyas Daghlas.
Needing to ‘rest your eyes’ for a daytime snooze could be more than just exhaustion, according to a new study that found the need to nap may be in your DNA. Stock image
Napping is ‘somewhat controversial’ says co-author Hassan Saeed Dashti, from the MGH Center for Genetic Medicine.
‘Some countries where daytime naps have long been part of the culture, such as Spain, now discourage the habit. Meanwhile, some companies in the United States now promote napping as a way to boost productivity,’ he said.
With this in mind, ‘it was important to try to disentangle the biological pathways that contribute to why we nap,’ added Dashti.
The UK Biobank, used to understand the genetic markers for napping in this new study, is a long term project aimed at investigating the contributions of genetic predisposition and environmental explore to disease.
Previous studies, by another co-author of this paper, Dr Richa Saxena, also used large biobank datasets to identify genes associated with sleep duration, insomnia and the tendency to be either a night owl or an early riser.
All participants were asked whether they nap during the day ‘never/rarely,’ ‘sometimes’ or ‘usually.’
A subset of participants wore activity monitors called accelerometers, which provide data about daytime sedentary behaviour, which can be an indicator of napping.
Genome regions linked to napping were more prominent in those volunteers who claimed to regularly take a nap during the day, the US team discovered. Stock image
This helped to confirm the self-reports of napping were accurate, as the motion detectors indicated restful time during periods volunteers said they would nap.
‘That gave an extra layer of confidence that what we found is real and not an artefact,’ says Dr Dashti.
Researchers independently replicated their findings in an analysis of the genomes of 541,333 people collected by 23andMe, the consumer genetic-testing company.
Also, a significant number of the genes near or at regions identified by the new study are already known to play a role in sleep, the authors explained.
One example is KSR2, a gene that the MGH team and collaborators had previously found plays a role in sleep regulation.
The data also revealed that there are three mechanisms within the genome that promote napping within some people and not others.
These include a propensity for sleep, that is ‘some people need more shut-eye than others’, and being an early riser as they may need to ‘catch up’ on sleep with a nap.
The other factor that could result in daytime napping is disrupted sleep from the night before, as a short nap can ‘make up for poor quality slumber’.
‘This tells us that daytime napping is biologically driven and not just an environmental or behavioural choice,’ says Dashti.
Some of these subtypes were linked to health concerns, such as large waist circumference and elevated blood pressure, though more research on those associations is needed, the team explained.
‘Future work may help to develop personalised recommendations for siesta,’ says Garaulet.
Furthermore, several gene variants linked to napping were already associated with signalling by a neuropeptide called orexin, which plays a role in wakefulness.
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,’ says Daghlas.
The findings have been published in the journal Nature Communications.