In 2017, the Nobel Prize in Medicine and Physiology was awarded to three chronobiologists who studied the molecular mechanisms of circadian rhythm . Jeffrey C. Hall, Michael Rosbash, and Michael W. Young secured the prestigious award with their research findings.
This may initially sound like material for Günther Jauch and "Who Wants to Be a Millionaire." However, our internal clock affects us all – especially when light and darkness influence our natural day-night rhythm . In the following text, you will learn about the role of blue light , whether blue light filters can be useful, and what science has to say about it.
Internal Clock – what is the circadian rhythm ?
The circadian rhythm describes our internal clock and thus biological processes that follow an approximately 24-hour rhythm (circadian = about one day).This includes, among other things, changes in body temperature, sleep-wake behavior, and hormone regulation. The hormone melatonin, which is primarily produced in the pineal gland, also plays an important role in regulating the sleep-wake cycle.
Our internal clock allows the body to adapt to the regular change between day and night. One of the most important external timekeepers for this is light.
How does light affect melatonin levels?
Our body reacts sensitively to external light conditions. When it gets darker in the evening, melatonin secretion increases under normal conditions. Melatonin is involved in regulating the sleep-wake cycle and signals to the body that the biological night is beginning.
The importance of light for our internal clock is also demonstrated by the example of jet lag: After a long flight across multiple time zones, the internal clock and the new local time do not initially align. Light at unusual times of the day can help shift the sleep-wake rhythm. Only gradually does the internal clock adjust to the new light-dark conditions.
Screen time and blue light
Whether smartphone, computer, or television: screens have become an integral part of our daily lives. A Bitkom survey from 2022, for example, showed that people in Germany spend an average of around ten hours a day in front of screens.
Why are we telling you this? With increasing screen time, the amount of time we are exposed to artificial light also rises – often into the evening hours.Light in the evening can influence our circadian rhythm and melatonin secretion. Factors such as timing, duration, intensity, and the light spectrum play a role.
How does blue light affect sleep?
As already explained, our body reacts sensitively to external light conditions. Visible light consists of different wavelengths. Blue light is located in the short-wavelength range of visible light and is both a component of natural daylight and the light of many digital screens.
For our internal clock, blue light is particularly interesting: Certain light-sensitive cells in the retina respond especially to short-wavelength light and are involved in the regulation of the circadian rhythm. Light in the evening can thus influence the natural melatonin secretion.This effect is being studied in research, among other things, in connection with the sleep-wake rhythm.
Blue light is not fundamentally bad. As a component of natural daylight, light significantly helps to synchronize our internal clock with the day-night cycle. Therefore, the timing and intensity of light exposure are also crucial.
Screens can represent an additional light source in the evening. Studies show that screen light can influence melatonin secretion under certain conditions. However, whether and how strongly this affects sleep depends on various factors.
So what can you do if you need to work on the screen in the evening or want to watch a movie with friends? This is where blue light filters and blue light filter glasses come into play.
Are blue light filter glasses useful?
One way to reduce the amount of short-wavelength light in the evening is through blue light filter glasses. Depending on the filter, they can block different areas and proportions of blue light. This changes the light spectrum that reaches the eye. Whether this also results in benefits for sleep has been scientifically investigated for several years.
A study with 21 college students, for example, examined how different lighting conditions during evening use of a computer monitor affect melatonin levels. The participants underwent three conditions: they either looked only at a monitor, received additional short-wavelength blue light, or wore orange glasses that filtered out short-wavelength light. Saliva samples were then used to determine the melatonin concentration.
Under additional blue light, the melatonin concentration was significantly lower than under the other two conditions. When only looking at the monitor, there was only a slight, statistically non-significant reduction compared to the control condition with orange glasses. The study thus provides evidence that evening light conditions can influence melatonin secretion.
The timing of light exposure also plays a role. In another study, the influence of blue-enriched light in the morning was investigated. Among other things, acute wakefulness-promoting effects and faster reaction times were observed. Blue light is therefore not fundamentally negative – it is also crucial when we are exposed to which light.
Blue light filter glasses themselves have also been studied in people with sleep problems.In a small randomized study, 14 individuals with symptoms of insomnia wore either amber blue light filter glasses or clear control glasses before bedtime. Among the filter glasses, various subjective sleep parameters and reported sleep quality improved.
When should one wear blue light filter glasses?
Blue light filter glasses are primarily offered for evening use. Depending on the model, they differ significantly in the wavelengths and the amount of blue light they filter out. Strongly orange or amber-tinted lenses typically filter a larger range of short-wavelength light than nearly clear lenses.
If you are still working on the computer in the evening, using your smartphone, or watching a movie, blue light filter glasses can be a way to reduce exposure to short-wavelength light.
If you already wear prescription glasses, there are so-called clip-ons that can be placed over the existing glasses. Alternatively, prescription glasses with an integrated blue light filter are also available.
Conclusion: Are blue light filters useful?
Light is one of the most important timekeepers for our internal clock. Especially in the evening, the timing, intensity, and light spectrum can influence melatonin secretion and the circadian rhythm. Those who sit in front of a smartphone, computer, or television late in the evening can specifically filter out a portion of the short-wavelength light with blue light filter glasses.
Individual studies provide evidence that evening light conditions can influence melatonin secretion.Positive changes in certain sleep parameters have also been observed in small studies for blue light filter glasses
Therefore, blue light filter glasses can be particularly interesting for people who regularly use screens in the evening and want to reduce their exposure to short-wavelength light. They offer a straightforward way to address this – without having to completely eliminate smartphones, computers, or movie nights from the evening program
