How light influences our sleep and wake rhythm

Red light supports your sleep and wake rhythm

Over the course of evolution, humans have created a survival advantage for themselves by adapting to time-varying environmental conditions, such as the change between day and night. This temporal organization of the organism has an effect on a large number of the body's own processes, such as cell division, heartbeat, breathing, sleep patterns and hormone levels.

In this article, you will find out what role light plays in our biological day-night rhythm and why this can easily get out of balance nowadays.

Light as a clock for our internal 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 clock. internal 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 phasesand, for example, produce and release appropriate hormones.

Our eyes can not only distinguish between day (light on) and night (light off), but also between morning, midday 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 role light plays in our health"). Scientists now agree that blue light is the most important indicator for the internal central clock and provides the body with a decisive indication of the current time of day and season. Another important source of information is red light.

The morning sun, for example, contains a high proportion of red light, which acts like a natural alarm clock for us after a 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 significantly: this high proportion of blue light signals to our body that it will be a few hours before night falls again. The body uses a lot of energy during this period in order to maintain a maximum state of alertness. This is also intended to protect the body from potential dangers that could arise from excessive heat or sunlight when falling asleep in the midday sun. A high level of blue light therefore increases our activity, but also puts the body on constant alert.

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

Artificial light: a will-o'-the-wisp as it is written in the book

With the control of fire, humans began to illuminate their world independently, which enabled them to see and carry out activities even after sunset. This is still the case today, albeit with two significant differences:

On the one hand, most people today spend most of their day indoors and therefore largely 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, for example, to LEDs and therefore also applies to Televisions, computers, smartphones (If you would like to find out more about the differences between natural and artificial light, you can read our article "The role light plays in our health").

As a lot of blue light signals to our body that it is the middle of the day and that it still needs to be active for several hours, our body also produces a lot of energy during this time to stay awake. That doesn't sound wrong at first if 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.

Above all, the constant turbo shift means a lot of stress for our bodies. By stressing our bodies for several hours a day and especially just before going to bed - through 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 can still fall asleep quickly or not, the recovery phase at cellular level starts much later and comes to a very abrupt end with the bedside lamp in the morning.

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

Improving the light balance - these are the options

The ideal, of course, would be to switch back to an all-natural lifestyle, i.e. 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 completely switch off from the digital world, you have to learn to dose artificial and natural light correctly if you want to take the strain off your body.

The golden rule is: Spend as much time outdoors as possible - 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 you can't do without artificial light or don't want to do without it in some situations, you can reduce the negative effects with a few simple hacks.

This can be remedied, for example, by adjusting the color temperature of displays (e.g. f.lux or iris), the use of light sources with the most natural color rendering index possible (CRI or ra >95) and - last but not least - the use of a blue blocker 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 be woken up by the natural sunrise, use red light as the first light source in the morning. Switch on the red light with the first alarm clock ring and let the red light rays affect your body. Similar to the morning sun, red light acts on your body like a gentle alarm clock and prepares it for the day ahead. What is particularly practical about this type of treatment is that it takes virtually no time at all, as you can go about your daily morning routine at the same time..... You can brush your teeth, get dressed...

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

Sources:

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