We have not been addicted to natural light from the Sun since the invention of the light bulb in 1879.
Nowadays, many people spend most of their day not only in artificially lit rooms, but also with screens – phones, computers and televisions. Recently, there have been concerns that looking at evening light screens can confuse your circadian rhythm, which is the internal clock that regulates our sleep-wake cycle.
I guess this means using a screen before bed could make it harder to fall asleep. In fact, there are many products you can buy to filter the blue light on your screens, which promise to improve your sleep quality.
Do these products actually work? Does the screen light change our circadian rhythm and make it harder 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 life forms, including plants, fungi and animals. In humans, the body clock is located 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 can also be adjusted in response to light.
Professor John Axelsson, a sleep research expert 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 regulate the circadian system. ; which allows the system to be dynamic and adapt to seasonal changes of day and night. “
Does technology change our circadian rhythm?
Many aspects of modern technology, from the basic light bulb to the newest touch screen phone, emit light. Professor Jamie Zeitzer of Stanford University says that “light mainly does two things to the clock. Set the clock time and change the amplitude or power of the clock ”.
As our circadian rhythm changes our 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 strong artificial light is actually used as therapy (called phototherapy) to help people who have very late biological clocks wake up and go to bed earlier.
The intensity of the light used for phototherapy is much higher than that emitted by the screens or bulbs we use. A 2014 study looked at a more realistic scenario: comparing melatonin levels and sleep quality to people who either read a normal book or an e-book before bed. They found that participants who read the e-book reduced their melatonin levels.
Dr Richardson of Western Australia University says: “There is evidence that 1.5 hours (or more) of light screen use reduces the natural increase in melatonin at night, and this effect can be compounded over several nights.” .
Importantly, she adds, “however, this does not seem to translate into more time to fall asleep.”
What does this mean for our sleep patterns?
Although we know that melatonin has many effects on the body and is associated with the sleep-wake cycle, we do not know exactly how small amounts of melatonin affect our sleep quality.
There are many studies on the use of technology and the quality of sleep or sleep time. Although many of these 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 printed books fell asleep 10 minutes before e-book readers. Other studies have compared people who have used products that have reduced blue light from screens to normal screen users. These studies found only a difference of 3-4 minutes in the time needed for sleep.
Because sleep is affected by many things, it is often difficult to make sure that you are only measuring the effect of time on the screen.
Another complication is highlighted by Dr. Richardson: “It is probably a two-way relationship between the use of technology and sleep. That is, the use of technology can affect sleep over time, however people with sleep problems can later increase the use of their technology.”
To eat
Technology, especially artificial light, is changing our circadian rhythm. We know this because we can see the differences in melatonin levels after using the screen.
What effect this 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-finding platform Metafact.io. Subscribe here to the weekly newsletter.