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Early-risers may have better mental health than night owls
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Using Mendelian randomization, researchers found that being a morning person was causally associated with better mental health; however, it did not affect BMI or risk for diabetes.
“We know that preference for morningness/eveningness is a real thing and although we already knew that a good portion of it is determined by our genes, we didn’t know which genes were important and therefore how our genes play a role,” Samuel E. Jones, PhD, research fellow at University of Exeter College of Medicine and Health, England, told Healio Psychiatry.
“Understanding the body clock and the processes that direct when and how we sleep is important because we know that evening people have higher risks of mental health disorders and have worse metabolic outcomes (greater risk of obesity and type 2 diabetes) over the course of their lives,” he continued. “Discovering the genetics of morningness/eveningness will enable us to start testing these hypotheses in an unbiased way.”
In the study, an international collaboration of researchers asked 250,000 participants of 23andMe and 450,000 UK Biobank participants if they were a morning or evening person. Then, they analyzed participants’ genomes to see which genetic loci they had in common that may affect their sleep patterns, according to a press release. The investigators also examined data from 85,760 UK Biobank participants with activity-monitor–derived measures of sleep timing.
The study findings indicated that being genetically programmed to rise early may lead to greater well-being and a lower risk for schizophrenia and depression, according to the release. The findings also showed the number of genetic loci that affect whether someone is an early riser increased from 24 to 351.
Jones explained that they found hundreds of genetic variants across the genome that affect a person’s preference to wake early or late, which emphasized the complexity of individual body clocks and the range of processes that affect people on the individual level.
“The genomic regions and genes we identified have pointed to some potentially interesting differences between morning and evening people; it seems that their clocks function in slightly different ways and that their eyes potentially interpret external light levels in different ways, causing their body clocks to be more/less effectively entrained (reset) by these light levels,” Jones said. “This work lays the foundations for a much greater understanding of why some people are at higher risk of disease and may even yield ways of combatting that risk through modifying sleep patterns (eg, by allowing people to match their sleep and activity patterns to their natural clock).”
Data from the wrist-worn activity trackers showed that the identified genetic variants could shift a person's natural waking time by up to 25 mins, according to the release. However, these genetic areas affect sleep timing, but not the quality or duration of sleep, according to the results. The genomic regions identified in the study include those central to circadian rhythms and genes expressed in the brain and in retinal tissue, according to the release.
“We can’t make any specific recommendations for clinicians because the research is still at an early stage, though our work will hopefully form the basis of future work that might be able to inform the medical profession and public policy,” Jones told Healio Psychiatry. “If we were to suggest anything at this stage, it may simply be to have a greater appreciation of the variety of chronotypes (seen through sleep and activity patterns), especially given that we’ve shown that some of your preference is hard-coded in your genes!” – by Savannah Demko
Disclosures: Jones reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.