How light influences our sleeping and waking rhythms

Red light supports your sleep and wake rhythm

In the course of evolution, humans have created a survival advantage for themselves by adapting to temporally varying environmental conditions, such as the change between day and night. This temporal organization of the organism affects a variety of endogenous processes, such as cell division, heartbeat, breathing, sleep behavior, and hormone levels.

In this article, you'll learn about the role light plays in our biological day-night rhythm and why it can easily get out of balance these days.

Light as a clock for our inner clock

Thanks to scientists, such as Hoff, Hollwich and Hattar et. al., we now know that the human eye transmits light impulses from the environment to our inner central clock, which in turn controls a number of time-related bodily functions. Through its internal clock, our body can better prepare for upcoming events, such as recovery or activity phases, and e.g.: produce and secrete appropriate hormones.

Our eyes can distinguish not only between day (light there) and night (light gone), but also between morning, noon and evening, for example. This is mainly due to the fact that the composition of sunlight varies depending on the time of day (see also the article "This is the role light plays in our health"). Scientists now agree that blue light is the most important clue for the internal central clock and provides the body with the decisive information about the current time of day and season. Another important informant is red light.

The morning sun, for example, contains a high proportion of red light, which acts on us like a natural alarm clock after the dark night: this triggers a series of energy-generating processes in our body that prepare our body for the day ahead.

Around midday, the blue light in sunlight increases sharply: this high blue light content signals to our organism that it will be a few more hours before night falls again. The body consumes a particularly large amount of energy during this period in order to maintain a maximum state of alertness. This is also intended to protect the organism from potential dangers that could arise from excessive heat or sunlight when falling asleep in the midday sun. A high level of blue light thus increases our activity, but also puts the body on constant alert.

As soon as the blue light spectra decrease again towards evening and the red light predominates again, our body concludes that night is approaching and it can begin to initiate the nightly regeneration phase.

Artificial light: a will-o'-the-wisp

With the control of fire, man began to light his world independently, which allowed him to see and pursue activities even after sunset. This is still the case today, but with two significant differences:

On the one hand, most people nowadays spend most of their day indoors and thus also mostly out of sunlight. On the other hand, most artificial light sources that we currently use in this country no longer have a natural light spectrum. They contain a high proportion of blue light, which is constantly high throughout the day. This applies to LEDs, for example, and thus also to televisions, computers, smartphones, etc. (If you want to learn more about the differences between natural and artificial light, you can read our article "This is the role of light in our health").

Since a lot of blue light signals to our organism that it's the middle of the day and it still has to be active for several hours, our body also produces a particularly large amount of energy during this time in order to stay awake. At first, that doesn't sound wrong when you have eight hours of office work ahead of you. But as tempting as the affectionately named "light espresso" may seem at first glance, it also has its downsides.

The permanent turbo gear means above all also a lot of stress for our body. By putting our body into this state for several hours a day and especially shortly before bedtime - by taking one last look at our cell phone - we deprive it of important rest phases and the opportunity to initiate nightly regeneration. Regardless of whether we are nevertheless able to fall asleep quickly or not, the recovery phase at the cellular level begins much later and comes to a very abrupt end with the bedside lamp in the morning.

Ergo: Our body cannot refuel enough during the night to generate enough energy to stay awake during the day. A prime example of a vicious circle that can result in chronic states of exhaustion, a high sense of stress, insomnia and emotional upsets.

Improve light budget - these are the options

The ideal, of course, would be to switch back to an all-around natural lifestyle, that is, to spend the whole day outside and not be exposed to artificial light. But for many of us, this is not compatible with either our professional or private lives. If you don't want to drop out of the digital world completely, you have to learn how to dose artificial and natural light correctly if you want to take the strain off your body.

The golden rule is to spend as much time as possible outdoors - ideally at sunrise and sunset. In a second step, the consumption of artificial light should be reduced to a minimum, especially in the evening. If artificial light cannot be dispensed with, or if you don't want to do without it in some situations, you can reduce the negative effects with a few simple hacks.

Remedies include adjusting the color temperature of displays (e.g. f.lux or Iris), using light sources with the most natural color rendering index possible (CRI or ra >95) and - last but not least - using blueblocker glasses and a red light lamp.

Supporting the sleep/wake rhythm with light therapy

If, for whatever reason, you don't have the opportunity to wake up to the natural sunrise, use red light as your first source of light in the morning. Turn on the red light with the first ring of the alarm clock and let the red light rays affect your body. Similar to the morning sun, the red light acts on your organism like a gentle alarm clock and prepares it for the day ahead. The most practical aspect of this type of application is that it does not take up any time, as you can go about your daily morning routine...... You can brush your teeth, get dressed...

Morning Sun: @imsdot via Twenty20
Office: @tanagorn.chinamornlert via Twenty20

References:

WHITTEN, Ari (2018): The Ultimate Guide to Red Light Therapy. Archangel Ink.
WUNSCH, Alexander (2019): The power of light. Why we need light and bad light makes us sick. 1st edition. riva: Munich.
WUNSCH, Alexander (2017): Light and Health 2017 - How healthy is our lighting? vimeo.com