Waking up an hour earlier could reduce risk of depression by 23%, study finds

A little change in the daily routine (wake up an hour earlier each day) could reduce the risk of depression by 23%, reveals a new genetic study published in the journal JAMA Psychiatry. Researchers from the University of Colorado-Boulder and the Broad Institute of MIT and Harvard they found that ehe chronotype, a person’s natural inclination to sleep at any given time, influences the risk of depression.

“We have known for some time that there is a relationship between time asleep and mood, but a question we often hear from doctors is, how quickly do we need to change people to see a benefit? ”he said. Celine Vetter, assistant professor of integrative physiology at the University of Colorado-Boulder. “We discovered that falling asleep even an hour earlier is associated with a significantly lower risk of depression. “

Previous observational studies have shown that night owls are twice as likely to suffer from depression as early risers, no matter how long they sleep. But because mood disorders themselves can disrupt sleep patterns, Researchers are struggling to understand what causes what. Other studies had small sample sizes, relied on single-point questionnaires, or did not take into account environmental factors that can influence both sleep time and mood, which can confuse the results. .

In 2018, Vetter published a large long-term study of 32,000 nurses showing that early risers were up to 27% less likely to develop depression within four years, but that begged the question: What does it mean to be an early bird? To get a clearer idea of ​​whether changing sleep time is truly protective and how much change is needed, the lead author of this research, Iyas Daghlas, relied on data from the DNA testing company 23 and me and the biomedical database British Biobank. So, used a method called “Mendelian randomization” What harnesses genetic associations to help decipher cause and effect.

“Our genetics are established at birth, so some of the biases that affect other types of epidemiological research tend not to affect genetic studies ”, He said Daghlas, graduate of the Harvard Medical School.

if you know that Over 340 common genetic variants, including variants of the PER2 ‘watch gene’, influence a person’s chronotype, Yes genetics collectively explain between 12% and 42% of our preference for sleep time.

Researchers evaluated anonymized genetic data on these variants from up to 850,000 people, including data from 85,000 who had used portable sleep trackers for 7 days and 250,000 who had completed questionnaires about sleep preferences. . This has given them a more detailed picture, so far, of how gene variants influence how we sleep and wake up.

In the largest of these samples, About a third of the subjects surveyed identified as morning larks, 9% were night owls and the rest were in the middle. Typically, the midpoint of sleep was 3 a.m., meaning they went to bed by 11 p.m. and woke up at 6 a.m.

Armed with this information, the researchers relied on a different sample that included genetic information as well as anonymous prescriptions and medical records Yes major depressive disorder diagnosis investigations. Using new statistical techniques, they asked: Who have genetic variants that predispose them to be early risers also have a lower risk of depression? The answer is a firm yes. Each point of sleep one hour before (midway between bedtime and wake-up time) it corresponded to a 23% lower risk of major depressive disorder.

This suggests that If a person who normally goes to bed at 1 a.m. goes to bed at midnight and sleeps the same time, they could reduce their risk by 23%; if they go to bed at 11pm, they could reduce it by about 40%.

Not easy of the study if those who are already early risers could benefit from waking up even earlier. But for those in the mid or nocturnal range, it would probably help to switch to an earlier bedtime.

Some research suggests that get more light exposure during the day, that early risers tend to have, causes a cascade of hormonal impacts that can influence mood. Others point out that Having a body clock, or circadian rhythm, that has different patterns than most people can in itself be depressing.

“We live in a society designed for morning people, and afternoon people often feel like they are in a constant state of misalignment with this social clock ”, Tenuous Daghlas.

The expert points out that thA large randomized clinical trial is needed to definitively determine whether going to bed early can reduce depression. “But this study definitely shifts the weight of evidence toward supporting a causal effect of sleep time on depression.”

For those who wish to switch to an earlier sleep schedule, Vetter gives this advice: “Keep your days bright and your nights dark.” Drinking your morning coffee outside, walking or cycling to work, and sifting through those electronics at night can help. “

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