We have not been dependent on natural light from the sun since the invention of the light bulb in 1879.
Nowadays, many people spend most of the day not only in artificially lit rooms, but also watching screens – phones, computers and TVs. Recently, there are fears that watching bright screens in the evening may confuse your circadian rhythm, which is the internal clock that regulates our sleep-wake cycle.
We would suggest that this means that using a screen before bed can make it difficult to fall asleep. In fact, there are many products you can buy to filter blue light from your screens that promise to improve the quality of your sleep.
Do these products actually work? Does the light on the screen change our circadian rhythm and does this make it difficult to fall asleep? The story is quite complicated.
How does the circadian rhythm work?
The circadian rhythm is an innate “body clock”
The hypothalamus secretes a hormone called melatonin. Melatonin is often called the “sleep hormone” because its levels are high at night but fall just before we wake up in the morning. The clock has an inherent rhythm, but can also be adjusted in response to light.
Professor John Axelson, a sleep research expert at the Carolingian Institute, explains that “the main clock … has an almost 24-hour internal rhythm and is very sensitive to light around dusk and dawn, so fine-tune the circadian system; which allows the system to be dynamic and to adapt to seasonal changes in the length of day and night. “
Does technology change our circadian rhythm?
Many aspects of modern technology, from the main bulb to the latest touchscreen phone, emit light. Professor Jamie Zeitzer of Stanford University says: “Light basically does two things with the clock. It adjusts the clock and changes the amplitude or power of the clock.”
Because our circadian rhythm changes melatonin levels, we can use levels of this “sleep hormone” to see what affects our clock in the body. 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 very slow biological clocks wake up and fall asleep earlier.
The intensity of the light used for phototherapy is much higher than that emitted by all the screens or bulbs we use. A 2014 study looked at a more realistic scenario: comparing melatonin levels and sleep quality in people who either read a normal book or an e-book at bedtime. They found that participants reading the e-book had reduced melatonin levels.
Dr Celle Richardson of the University of Western Australia said: “There is evidence that 1.5 hours (or more) of using a bright screen reduces the natural increase in melatonin at night and this effect can be complicated for several nights.”
Importantly, she adds, “but that doesn’t mean it takes longer to fall asleep.”
What does this mean for our sleep patterns?
Although we know that melatonin has many effects in the body and is related to the sleep-wake cycle, we do not 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 find a link between screen time and sleep, correlations are often weak and do not indicate that increased screen time causes sleep problems.
For example, a 2014 study found that, on average, participants who read printed books fell asleep 10 minutes before e-book readers. Other studies compare people who have used products that reduce blue light from screens to normal screen users. These studies found only a 3-4 minute difference in the time needed to fall asleep.
Because sleep is affected by many things, it is often difficult to make sure that you are only measuring the effect of screen time.
Another complication was highlighted by Dr. Richardson: “There is a possible two-way link between the use of technology and sleep. That is, the use of technology can affect sleep over time, but people who have sleep problems may subsequently increase their use. of its technology. “
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, especially the time it takes to fall asleep, is not yet clear.
An 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 to their weekly newsletter here.