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A third of the British public describe themselves as "night owls" – preferring to get things done in the evening. Winston Churchill, Marcel Proust or Elvis Presley may all have belonged to that category too, but that does little to alleviate how sluggish you feel when your alarm rings on a weekday.
New research, published in Nature Communications, doesn’t do much to help you get up but it does shed some light on why we count ourselves as morning or evening people. The answer? It’s not anything you’re doing – it all comes down to your genes.
That’s something that we somewhat knew already. Previous research had identified a total of 24 genes that determine the way the human body clock is regulated, known as our circadian rhythm – that is, our internal cycle of sleepiness and alertness. A trio of biologists won the Nobel Prize in medicine in 2017 for discovering the “period gene”, which encodes a protein at night time, letting our bodies know that it is time to sleep, and which then degrades during the day.
The period gene was one of the 24 – the new Nature study has brought that number to 351. “Depending on how many of those genes you carry, you can be anywhere on the scale of ‘morningness,’” says Michael Weedon, a bioinformatics at the University of Exeter Medical School, who led the study. "But our research showed that the top five per cent with the most of those 351 genes go to sleep on average 25 minutes earlier than the five per cent who carry the least."
In other words, there are 351 reasons that you could get tired early, or on the contrary feel more productive once night has fallen, and there is not much you can do about it, because it’s all genetically predefined.
But the study has not only come up with a list of genes: it has also looked at where those genes are most likely to be switched on in the body. Lead author Samuel Jones from the University of Exeter Medical School explains that different parts of our bodies carry different types of tissue. And while all tissues contain all our genes, all our genes are not switched on in all our tissues.
“The genes we found to be related to our circadian rhythms tend to be switched on a lot more in the brain and in the retina,” he says. “This helps us map what parts of the body are important in creating morning and evening people.”
That those genes are activated in our brains is not very surprising, Jones continues, as it is already well-known that the brain is our body's’ “master-clock”. More specifically, it is in a zone of the hypothalamus called the suprachiasmatic nucleus (SNC) that the action happens: the SNC contains an oscillator that is thought to “set” your body on the time of the day, according to different signals it receives from the environment you are finding yourself in.
One signal the SNC works with is light. When the retina signals that it is night time, for example, our brain releases a sleep-inducing hormone called melatonin. And that is why it is significant that Weedon and Jones’ research localises ‘morningness’ genes in the retina. Essentially, the way we process light signals – and therefore the way that we signal, or not, to our body that it is time to sleep – could be a matter of genetics.
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Two of the genes that the researchers found had mutations inside which potentially alter the way the gene works to detect light. “We did know that light levels were used to train our body clocks,” says Jones, “but we didn’t know that the way we detect them could differ between morning and evening people. This shows that these differences could be happening at a fundamental level – the genetic one.”
So you have no control over whether you are a night owl or early riser. What’s the big deal? Well, that’s where the study gets interesting, because being an evening person has already been widely associated with a variety of mental health conditions such as depression and schizophrenia. Last year, a report found that chances of having depression, of having a bipolar disorder and of being lonely all increased for those who reported higher levels of activity at night.
But this is a chicken and egg situation: do mental health issues cause people to have disrupted sleeping patterns, or is it the other way round? “Genetics always come first,” says Jones. “So this helps us understand which is the cause in the relationship between circadian rhythms and disease.”
Of course, it is not always clear-cut, with some diseases like schizophrenia also having genetic roots. But, according to Jones, it is safe to say that you are genetically predisposed to being a morning or evening person, and that this will then go on to affect your risk of mental health issues.
One potential way forward would be to look at whether mental illnesses could arise from a mismatch between lifestyle and genetic predisposition. Jones and Weedon both agree: people who carry the ‘morningness’ genetics are better aligned to the nine-to-five lifestyle of modern society. Fighting against your genetics can’t be good for your mental health – and actually, that whether that is the case will be the focus of the researchers’ next study.
In the future, this could justify a call for more flexible work policies that are understanding of the fact that some people work better at different times. Something that would not only boost productivity, but also improve workers’ mental health.
Those are still long-term aims for the researchers, so it may be a bit early for you to jump on to the Munich Chronotype Questionnaire – “the gold standard”, according to Weedon, for assessing whether you are a morning or evening person. The best way to determine to which type you belong is to pay attention to how you feel, he adds. It may be time to indulge guilt-free in the 3PM nap you fight against every day in the office.
This article was originally published by WIRED UK
