Technology really changes human circadian rhythms, scientists say

Since the invention of the incandescent lamp in 1879, we have no longer relied on natural light from the sun.

Today, many people not only spend most of the day in artificially lit rooms, but also look at screens – telephones, computers, and TVs. Recently, there have been concerns that watching bright screens at night may confuse your circadian rhythm, the internal clock that regulates our sleep-wake cycle.

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

Do these products really work? Does screen light change our circadian rhythm and make it more difficult to fall asleep? The story is quite complicated.

How does the circadian rhythm work?

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

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

Professor John Axelsson, an expert in sleep research at the Karolinska Institute, explains that the “master clock … has an intrinsic rhythm of almost 24 hours and is very sensitive to light around dusk and dawn, so to fine-tune the circadian system. the system must be dynamic and adapt to seasonal changes in the duration of day and night. “

Is technology changing our circadian rhythm?

Many aspects of modern technology, from the base lamp to the latest touchscreen phone, radiate light. Professor Jamie Zeitzer of Stanford University says, “Light mainly does two things to the clock. It sets the time of the clock and it changes the amplitude or strength of the clock.”

Since our circadian rhythm changes melatonin levels, we can use the levels of this ‘sleep hormone’ to see what affects our body 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 a very slowed biological clock to wake up and go to sleep earlier.

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

Dr. Cele Richardson of Western Australia University says, “There is some evidence that using a bright screen for 1.5 hours (or more) reduces the natural nighttime melatonin build-up, and this effect may intensify over several nights.”

Importantly, she adds, “However, this doesn’t 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 sleep quality.

There are numerous studies looking at technology use and sleep quality or the time it takes to fall asleep. While many of these find a link between screen time and sleep, the correlations are often weak and don’t show that longer screen time causes sleep problems.

For example, the 2014 study found that participants who read the printed books fell asleep an average of 10 minutes earlier than the e-book readers. Other studies compared people who used products that reduced blue light from screens to 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 many things, it is often difficult to be sure that you are just measuring the effect of screen time.

Another complication is highlighted by Dr. Richardson: “A bi-directional relationship between technology use and sleep is likely. That is, technology use can affect sleep over time, but people who have sleep problems may later increase their technology use.”

The takeaway

Technology, especially artificial light, is changing our circadian rhythm. We know this because we can see differences in melatonin levels after using the screen.

What effect this has on our sleep, in particular the time it takes to fall asleep, is not yet clear.

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

This expert response has been published in conjunction with the independent fact-checking platform Subscribe to their weekly newsletter here.