We no longer depend on natural sunlight since the invention of the electric light bulb in 1879.
Nowadays, many people spend most of the day not only in artificially lit rooms, but also looking at screens – phones, computers and televisions. Recently, there have been concerns that looking at bright screens at night could disrupt your circadian rhythm, which is the internal clock that regulates our sleep-wake cycle.
We’ll assume this means that using a screen before bed might make it harder to fall asleep. In fact, there are many products you can buy to filter the blue light from your screens, which promises to improve the quality of your sleep.
Do these products actually work? Does screen light alter 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” found in many forms of life, 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 referred to as the “sleep hormone” because its levels are high at night but drop just before waking up in the morning. The clock has an inherent rhythm, but it can also be adjusted in response to light.
Professor John Axelsson, 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 refine the circadian system; this allows the system to be dynamic and adapt to seasonal changes in the length of the day and night. “
Is technology changing our circadian rhythm?
Many aspects of modern technology, from the basic bulb to the latest touchscreen phone, emit light. Stanford University Professor Jamie Zeitzer says, “Light does two main things on the clock. It sets the clock time and it changes the amplitude or strength of the clock.”
As our circadian rhythm changes levels of melatonin, 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 the production of melatonin in humans.
Interestingly, super bright artificial light is actually used as a therapy (called phototherapy) to help people with severely delayed body clocks wake up and fall asleep earlier.
The intensity of the light used for phototherapy is much higher than that emitted by the screens or bulbs that 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 e-book before bed. They found that participants who read the e-book had reduced melatonin levels.
Dr Cele Richardson of Western Australia University says: “It has been proven that an hour and a half (or more) of using a bright screen reduces the natural increase in melatonin at nighttime, and this effect may occur. ‘worsen over several nights. “
Above all, she adds, “however, this does not seem to translate into falling asleep any longer.”
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 quality of sleep.
Many studies focus on the use of technology and the quality of sleep or the time it takes to fall asleep. Although many of them find a correlation between screen time and sleep, the correlations are often weak and they do not show that increasing screen time causes sleep problems.
For example, the 2014 study found that, on average, participants who read print books fell asleep 10 minutes before e-book readers. Other studies have compared people who used products that reduced blue light from screens to normal screen users. These studies only found a difference of 3 to 4 minutes in the time it took to fall asleep.
Since sleep is affected by many factors, it is often difficult to ensure that it is just the effect of screen time that you are measuring.
Another complication is pointed out by Dr Richardson: “A two-way relationship between the use of technology and sleep is likely. In other words, the use of technology can affect sleep over time, but people who have trouble sleeping may subsequently increase their use of 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.
The 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: Is technology changing our circadian rhythm?
This expert response was published in partnership with the independent fact-checking platform Metafact.io. Subscribe to their weekly newsletter here.