The study looked at nearly 90,000 responses to a web survey, in which 23andMe clients described their morning or evening preferences. All the participants had their genomes sequenced as part of the company's Personal Genome Service.
'In this study we set out to discover more about an individual's preference toward early rising, and were able to identify the genetic associations with 'morningness' as well as ties to lifestyle patterns and other traits,' Dr Youna Hu of 23andMe and first author of the study told Medical Daily.
Out of 135,447 client responses to surveys, the researchers identified 89,289 individuals of European ancestry with clear morning or evening preferences and they analysed their genomes looking for patterns. The study was published in Nature Communications.
They found 15 regions of the genome that were associated with being a morning person, and seven of these were located near to genes that were already known to be linked to circadian rhythm, or body clock.
These genes include: RGS16 and FBXL3, which affect the length of the circadian period in mice; RASD1, involved in linking of circadian rhythms to light exposure in mice; VIP, linked to rapid eye movement (REM) in rabbits; and PER2, HCRTR2, and PER3, which are associated with sleep disorders in humans.
The surveys also found that 'morning people' sleep more soundly and are less likely to need more than eight hours of sleep per night or to suffer from insomnia. Early risers are also less likely to have a high body mass index or to be depressed. However, researchers emphasised that these were just correlations and that they had not identified a cause-and-effect relationships between these characteristics and a preference for mornings.
'We think of our preferences as things that we come up with – things that are kind of spontaneous parts of who we are – but they do have a basis in biology,' David Hinds, a statistical geneticist at 23andMe and a co-author of the study, told The Verge. 'I think it's just very interesting for people to see how their biology influences who they are.'
Dr Daniel MacArthur, a geneticist from Massachusetts General Hospital and Harvard Medical School who was not involved in the study, told Wired: 'The genetic region they discover here give us a window into the biology of sleep.'
Last year, 23andMe made a deal Reset Pharmaceuticals to develop drugs targeting the body’s circadian rhythms (see BioNews 794).