Since the invention of the light bulb in 1879, we have not depended on the natural light of the Sun.
Today, many people spend most of the day not only in artificially lit rooms, but also looking at screens: telephones, computers, and televisions. Lately, there have been concerns that looking at bright screens in the evening can confuse the circadian rhythm, which is the internal clock that regulates our sleep-wake cycle.
We would assume that this means using a screen before bed can make it difficult to fall asleep. In fact, there are many products you can buy to filter the blue light from screens, which promise to improve your sleep quality.
Do these products really work? Does the screen light change our circadian rhythm and does this make it difficult to fall asleep? The story is quite complicated.
How does 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 a “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 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 about 24 hours and is very sensitive to light at dusk and dawn, so to fine-tune the circadian system, which allows 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 new touchscreen phone, emit light. Professor Jamie Zeitzer of Stanford University says that “light does two things primarily on the clock. It is setting the time of the clock and changing 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 affects our body’s 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 who have a very late biological clock 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 light bulbs we use. A 2014 study examined a more realistic scenario: comparing melatonin levels and sleep quality of people reading a normal book or e-book before bedtime. They found that participants who read the e-book had reduced melatonin levels.
Dr Cele Richardson of Western Australia University says that “there is evidence that 1.5 hours (or more) of bright screen use reduces the natural nocturnal increase in melatonin, and this effect can be grouped over several nights. “.
It is important to note that he adds, “However, this does not seem to translate into taking longer 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 much melatonin affects our sleep quality.
There are numerous studies that analyze the use of technology and the quality of sleep or the time it takes to fall asleep. While many of these find a correlation between screen time and sleep, the correlations are often weak and do not show that increasing screen time causes trouble sleeping.
For example, the 2014 study found that, on average, participants who read printed books fell asleep 10 minutes earlier than e-book readers. Other studies compared people who used products that reduced the blue light of screens to normal screen users. These studies found only a 3-4 minute difference in the time it took to fall asleep.
Because many things affect sleep, it is often difficult to make sure that only the effect of screen time is measured.
Another complication is highlighted by Dr. Richardson: “There is likely to be a two-way relationship between the use of technology and sleep. That is, the use of technology can affect sleep over time, all and that people who have trouble sleeping can later increase their use of technology. “
Takeaway food
Technology, specifically 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, especially the time it takes to fall asleep, is still unclear.
Article based on 4 expert answers to this question: is technology changing our circadian rhythm?
This expert response was published in collaboration with the independent fact-checking platform Metafact.io. Subscribe here to their weekly newsletter.