Technology is really changing human circadian rhythms, scientists say


We have not relied on natural light from the Sun since the invention of the light bulb in 1879.

Today, many people spend most of the day not only in artificially lit rooms, but also looking at screens – telephones, computers, and televisions. Recently, concerns have arisen that looking at bright screens at night could confuse your circadian rhythm, which is the internal clock that regulates our sleep-wake cycle.

We would assume this means that wearing a screen before bed could make it difficult to fall asleep. In fact, there are many products you can buy to filter blue light from your screens, which promises to improve the quality of your sleep.

Do these products really work? Does the light from the screen change our circadian rhythm, making it difficult to fall asleep? The story is quite complicated.

How does the circadian rhythm work?

The circadian rhythm is an innate ‘body clock’ present in many forms of life, including plants, fungi, and animals. In humans, the biological clock is located in the hypothalamus.

The hypothalamus releases a hormone called melatonin. Melatonin is often referred to as the ‘sleep hormone’ as its levels are high at night but drop just before we wake up in the morning. The watch has an intrinsic rhythm, but it can also be adjusted in response to light.

Professor John Axelsson, an expert in sleep research at the Karolinska Institute, explains that the “master clock … has an intrinsic rhythm close to 24 hours and is very sensitive to light at dusk and dawn, so it adjusts the circadian system, allowing the system to be dynamic and adapt to seasonal changes in the length of day and night. “

Is technology changing our circadian rhythm?

Many aspects of modern technology, from the basic light bulb to the latest touchscreen phone, emit light. Stanford University professor Jamie Zeitzer says that “light does primarily two things with the clock. It is setting the clock time and it is changing the amplitude or strength of the clock.”

As our circadian rhythm changes the levels of melatonin, we can use the levels of this ‘sleep hormone’ to see what is affecting our biological clock. Several studies have shown that bright artificial light suppresses melatonin production in humans.

Interestingly, very bright artificial light is actually used as a therapy (called phototherapy) to help people with severely delayed body clocks to wake up and fall asleep earlier.

The intensity of the light used for phototherapy is much greater than that emitted by the screens or bulbs that we use. A 2014 study looked at a more realistic scenario: comparing melatonin levels and sleep quality of people who read a regular book or e-book before bed. They found that the participants who read the e-book had lowered levels of melatonin.

Dr Cele Richardson from the University of Western Australia says that “there is evidence that 1.5 hours (or more) of bright screen use reduces the natural surge in melatonin overnight, and this effect can be aggravated over several nights “.

Importantly, “however, this does not seem to translate into taking longer to fall asleep.”

What does this mean for our sleep patterns?

While we know that melatonin has many effects on the body and is associated with the sleep-wake cycle, we don’t know exactly how reduced amounts of melatonin affect our quality of sleep.

There are numerous studies that look at the use of technology and the quality of sleep or the time it takes to fall asleep. Although many of them find a correlation between screen time and sleep, the correlations are often weak and do not show that increased screen time causes sleep problems.

For example, the 2014 study found that, on average, participants who read print books fell asleep 10 minutes earlier than e-book readers. Other studies compared people using products that reduced blue light from screens with normal screen users. These studies found only a 3-4 minute difference in the time it took to fall asleep.

Since sleep is affected by so many things, it is often difficult to make sure that what you are measuring is just the effect of screen time.

Dr. Richardson highlights another complication: “There is likely a two-way relationship between technology use and sleep. That is, technology use can affect sleep over time, but people who have trouble sleeping they can subsequently increase their use of technology. “

Food to go

Technology, specifically artificial light, changes our circadian rhythm. We know this because we can see differences in melatonin levels after screen use.

It is not yet clear what effect this has on our sleep, particularly the time it takes to fall asleep.

Article based on 4 expert answers to this question: Is technology changing our circadian rhythm?

This expert response was published in association with independent fact-checking platform Metafact.io. Sign up for their weekly newsletter here.

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