September 20, 2020

The genome of early risers protects them from depression | Science

The genome of early risers protects them from depression | Science



Scientists call Lark The type of person that gets out of bed easily and finds the highest productivity of the day in the morning. Your chronotype – this is the technical name that each pattern of sleep and activity receives – is the opposite of that of the owls, who work better at night and go to bed and get up late, according to social conventions. A new study, published today in Nature Communications, reveals that those who are genetically programmed to wake up soon have less risk of suffering from mental illnesses such as depression or schizophrenia. In addition, they declare that they feel better than others.

It was known that the genetics of each individual conditions their ability to follow one or another schedule. But previous research had only identified a handful of genes relevant to the chronotype, and those studies that have sought a link to health have only found correlations, not causality. The new work, which has analyzed the genome of 697,828 people, concludes that there are at least 351 genes that predispose a person to be owl or Lark, hundreds more than the 24 that were known. In determining which genetic variants share the Larks, researchers have been able to establish a cause and effect relationship between being early and enjoying greater mental health.

The international research team, led by biologists from the University of Exeter (United Kingdom), analyzed the genomes of British citizens collected in the research database UK Biobank and also data from the US private company 23andMe, which sells personal tests of genetics. Each participant had indicated their sleep pattern previously in a survey. However, the scientists were looking for a more objective measure of the chronotype, so they included in the analysis data of 85,760 people whose sleep hours were recorded with an activity bracelet.

The study confirms that those who were genetically predisposed to be Larks they slept on average 25 minutes earlier on the day they owls. They obtained this measure when comparing the 5% of people who had more early genes in their DNA with the 5% who had less. The time difference between one end of the spectrum and the other seems modest, but it is statistically significant. There were no differences, however, in the duration or quality of sleep.

Although the morning papers declare better well-being in general and it was detected that they suffered less cases of depression and schizophrenia, researchers have not found that early risers protect against other diseases, such as diabetes or obesity. "This was a bit surprising," says biologist Samuel Jones of the University of Exeter, one of the authors of the study. "Many investigations have found that owls they have a worse metabolic regulation and maybe a risk of diabetes and obesity. But those studies tend to be correlated; By using genetics, we have been able to infer the cause and the effect. "

Jet lag Social

One possibility to explain the previous results is that there is a third common factor for those who go to bed late and those who suffer from these diseases, explains Jones. But it is also possible that it owl not intrinsically bad for health, but the harmful thing is to get up early for social and work commitments when genetics predisposes you to the contrary. This produces imbalances in the internal biological clocks, or jet lag social, and has proven negative consequences for health.

Precisely, many of the genes identified in this study are responsible for regulating the circadian clocks of the body, biochemical processes that govern the periodicity of cellular activities. Jones notes that "the circadian rhythm can be trained, to some extent," especially trying to maintain a routine to always lie down and wake up at the same time. "If you are a person of late, you can achieve a great deal of the way towards being a person of tomorrow," explains the researcher. But he adds: "The genes will stop you in the final stretch because the owls They have an internal clock that runs a little slower. That is genetic and can not be changed. "

The harmful thing is to get up early because of social and work commitments when genetics predisposes you to the contrary

Maria José Martínez, the coordinator of the Chronobiology Group of the Spanish Sleep Society (SES), who did not participate in this study, assures that "if we lived in a society where everyone could organize their schedules (work, sleep, etc.) freely, it would be indifferent to health to be morning or evening". But Martínez, who is also manager of the Kronohealth circadian consulting firm, says that for the owls that would only be fulfilled "as long as we use intense artificial light during waking hours and avoid light during sleep hours".

The incidence of light is an important factor because it stops the production of melatonin, a hormone that promotes sleep. A tip to advance the routine when the body does not ask for it is exposed to light, natural or lamp, first thing in the morning, even before waking up. Interestingly, Jones and his colleagues have found that some of the 351 genes associated with the chronotype are expressed in the cells of the retina, in the eye, suggesting that "the Larks they probably perceive light in a slightly different way than owls", According to the author of the study.

Other genes that have been identified are expressed in the hypothalamus, a region of the brain with functions of regulation of sleep and wakefulness, some involved in the metabolism of insulin and those that influence the processing of stimulants, such as caffeine and nicotine . All this points to intrinsic physiological differences between owls Y Larks, but detailed studies will be necessary to unravel how or why each of these genetic variants affect the chronotype, and by extension mental health.

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