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Our body clock, or circadian rhythm, tells our brain when to sleep, our gut when to digest and controls our activity during the day. Photo: Shutterstock

Circadian rhythm isn’t just about sleep – it affects our immune system, metabolism, fertility and more, doctors explain

  • Let your body clock get out of whack and it isn’t only your sleep that’s disrupted, but also your digestion, and your immunity to diseases such as cancer
  • Technology is to blame for this disruption, with light from mobile phones and televisions tricking our brains into staying awake, but it’s also the solution

These are tiring times. Just look at how excited people are to sleep. We have never been more focused on it nor so willing to spend money to ensure a good night’s sleep.

The global sleep market now surpasses US$432 billion, and is set to hit $585 billion by 2024 – spent on everything from mattresses and sleep aids to technology that tracks your sleep and apps designed to help you sleep.

Magazines and wellness journals overflow with articles about how vital sleep is to everything from health and cognition to productivity and fitness.

Still, all the attention we’re paying to sleep and the money we’re spending does not seem to be doing us much good. On average, one in three people say that they sleep badly, with one in 10 reporting they suffer from chronic insomnia.

A good night’s sleep is vital to everything from health and cognition to productivity and fitness. Photo: Shutterstock

While we struggle to find the answer to perfect sleep, scientists say we may be asking the wrong question in the first place.

All those articles touting the importance of sleep are not wrong. It’s just that by focusing on sleep so single-mindedly we might be missing the big picture, and neglecting a cycle that is fundamental to almost all aspects of our health and well-being, including sleep: our circadian biology.

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Circadian science is still in its early days – scientists working on it took home the Nobel Prize in medicine in 2017 – but since then the breakthroughs have been coming thick and fast.

This branch of science views the human body as a system of clocks built into our DNA.

There is a so-called “master clock” in the brain’s hypothalamus, called the suprachiasmatic nucleus, which keeps the body on a 24-hour schedule thanks to signals triggered by light reaching our optic nerves. That master clock is responsible for keeping smaller clocks in our major organs “on time”.

“You can think of the clock in the brain as the conductor for the orchestra. And then the clocks that we have all over the rest of the body are the players in the orchestra and they need to be in time with the conductor. You want your stomach clock to be aligned with your pancreas clock, to be aligned with the liver clock,” says Dr Steven Lockley, associate professor of medicine at Harvard and one of the world’s top experts on circadian rhythms and sleep.

The body’s natural circadian rhythm affects more than just your sleep patterns. It can influence other biological processes like the immune and digestive systems. Photo: Shutterstock

“So yes, sleep is one important part, as is alertness, performance, and mood, but it goes far beyond that, to things like our metabolism.”

When working right, this complex network of clocks – set to the master clock in our brain – dictates not only when we sleep but also our digestion and metabolism, our fertility, our immune system, our moods and hormones, and even regulates our body temperature.

The scary thing is that for most modern humans, things are not working right at all.

An illustration of the human eye with timepieces in it and a person adjusting them, is an example of how our daily circadian rhythms work. Photo: Shutterstock

“Humans, their entire biology evolved around the 24-hour cycle of the sun. And we’ve never destroyed that natural light-dark regularity cycle more than we have today,” says Beth McGroarty, vice-president of research and forecasting for the Global Wellness Summit and Global Wellness Institute.

“We’re blasting our faces with our mobile phones at night, and ever bigger televisions, the light pollution in our world is insane. People’s work schedules don’t have anything to do with natural solar time.”

Some people call it a “light-mare”, she adds.

Lockley says: “If we mess with lights, for example when we do shift work or if you travel across time zones, then we mess with the timing of the clock.

It’s time to listen to our internal clock, not the one on our bedside table. Photo: Shutterstock

“And that’s what causes the problems associated with jet lag. While people focus on the sleep performance and mood issues, they’re really just the easiest things to notice, but jet lag also will disrupt our immune system, our heart rhythms, our reproductive function, our glucose regulation.”

Circadian science might also hold the answers to why some current fitness and wellness trends are so effective.

Take, for example, intermittent fasting. Scientists now think that this year’s hottest diet trend might be so effective less because of metabolism or calorie intake, and more because it is closely in line with our natural circadian rhythms.

Beth McGroarty, vice-president of research and forecasting for the Global Wellness Summit and Global Wellness Institute. Photo: Beth McGroarty

Those working in the wellness industry are predicting a major shift towards circadian health. Writing in this year’s Global Wellness Trends Report: The Future of Wellness 2020, McGroarty predicted: “Less focus on all the generic sleep solutions and a keen new focus on circadian health optimisation for not only sleep but for all the brain and body systems that are controlled by the circadian clock. It means that the timing of biology will become something we need to measure and manage, and light will be a central part of any solution.”

While technology is responsible for disrupting our circadian rhythms, it also offers the only solutions to repairing them and returning us to some kind of normalcy. Various smart lighting schemes are already popular.

They range from expensive comprehensive light systems that change automatically throughout the day to suit your personal schedules and circadian needs, to less sophisticated solutions such as using blue bright light bulbs in the daytime, and red bulbs at night.

Examples of the Timeshifter sleep app. Photo: Shutterstock
There are also apps, like Timeshifter, which use your personal circadian rhythm to suggest schedules of sleep and behaviour that can help ameliorate jet lag and bring you back into circadian balance more generally.

It is hard to exaggerate how much circadian rhythms might be influencing our health.

Lockley sees a clear correlation between circadian health and serious diseases like diabetes and even cancer.

“When the circadian rhythm is compromised, the immune function is compromised. We now think that circadian health plays a role in making us more susceptible to disease or to infection.

“And there’s a cancer risk,” he says, “because the tumour cells are also circadian. And when we mess with our clock, so we give those type of cells a chance to gain a foothold.”

Dr Steven Lockley is associate professor of medicine at Harvard, and one of the world’s top experts on circadian rhythms and sleep. Photo: Harvard

He is convinced that the more we learn about circadian health, the more even basic medical services will change: what time your medical tests are scheduled, when you take certain medications. In the future, even surgeries will be adapted to your personal internal clock.

“There’s going to become a lot more focus on your internal clock,” says Lockley, “rather than the clock on the wall.”