We have not been dependent 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 watching screens – telephones, computers and TVs. Recently, there has been concern that looking at bright screens in the evening may confuse your circadian rhythm, it is the internal clock that regulates our sleep-wake cycle.
We assume that this means that it is difficult to fall asleep if you use a screen in front of the bed. There are actually many products you can buy to filter out the blue light on your screens, which will improve your sleep quality.
Do these products really work? Does screen light change our circadian rhythm, making it harder to fall asleep? The story is quite complicated.
How does the circadian rhythm work?
The circadian rhythm is an innate ‘body clock’ that occurs in many life forms, 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 called the ‘sleep hormone’ because 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 ‘main clock … has an intrinsic rhythm of almost 24 hours and is very sensitive to light around dusk and dawn, to refine the circadian system; the system must be dynamic and adapt to the seasonal changes in day and night. “
Is technology changing our circadian rhythm?
Many aspects of modern technology, from the basic light bulb 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.”
As our circadian rhythm changes melatonin levels, we can use the levels of this ‘sleep hormone’ to see what is affecting 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 very delayed biological clocks wake up and go to bed earlier.
The intensity of the light used for phototherapy is much higher than the screens or light bulbs we use. A 2014 study looked at a more realistic scenario: melatonin levels and sleep quality are compared in people who read a regular book or an electronic book before bed. They found that the participants who read the electronic book lowered the melatonin levels.
Dr Cele Richardson of the University of Western Australia said: “There is evidence that using bright screens for 1.5 hours (or more) reduces the natural increase in melatonin during the night, and this effect can be compounded over several nights. word. “
Importantly, she adds, “it does not seem to take long to fall asleep.”
What does this mean for our sleep pattern?
Although we know that melatonin has many effects in the body and is associated with the sleep-wake cycle, we do not know exactly how a reduced amount of melatonin affects our sleep quality.
There are numerous studies that look at the use of technology and sleep quality or the time it takes to fall asleep. Although many of these find a correlation between screen time and sleep, the correlations are often weak and do not show that the increased screen time causes problems with sleep.
The 2014 study, for example, found that participants who read the printed books fell asleep ten minutes before the e-book readers. Other studies have compared people who use products that reduce the blue light of screens to normal screen users. These studies found only a difference of 3-4 minutes in the time it took to fall asleep.
Since sleep is affected by many things, it is often difficult to make sure that it is only the effect of screen time that you are measuring.
Another complication is emphasized by Dr. Richardson: “A two-way relationship between technological use and sleep is likely. That is, technological use can affect sleep over time, but individuals who struggle to sleep may increase their technological use thereafter.”
The takeaway
Technology, specifically artificial light, does change our circadian rhythm. We know this because we can see the differences in melatonin levels after using the screen.
The effect it has on our sleep, especially the time it takes to fall asleep, is not yet clear.
Article based on 4 expert answers to this question: Does technology change our circadian rhythm?
This expert response was published in partnership with the independent fact-checking platform Metafact.io. Subscribe to their weekly newsletter here.