Living organisms started gaining the ability to see light a long time ago but we still don’t know exactly when this began. The oldest fossil of eyes found till now has been dated back to more than half a billion years ago. So, it’s clear that the evolution of our eyes happened over a long period of time. Also, over this period, sight became a significant part of how we perceive reality.

Not only does light make it possible for us to see things, but it also has a psychological impact on us. Our mood can be affected by the color of light we see and its intensity. The same is true of sleep. Many studies like this have shown that light, its duration of exposure, and its brightness influence our quality of sleep. To understand why this happens, we need to understand circadian rhythm first.

Circadian rhythms are basically 24-hour cycles of physical, mental, and behavioral changes in the body. These cycles are constantly running in the background and carrying out crucial processes. The sleep-wake cycle is one of the more important circadian rhythms. This cycle is synchronized with an internal biological clock that is located in the brain (known as the hypothalamus).

This internal clock is affected by environmental factors such as light and temperature. It is especially sensitive to light which is why circadian rhythms are so connected to the day-night cycle of the planet. Studies have shown that light affects our circadian clock in two main ways.

The first way is by acutely suppressing melatonin. But, what does that mean? Well, melatonin is a hormone that is made by the pineal gland in the brain. It is an important physiological regulator of the sleep-wake cycle. It serves as the time cue to the biological clock and promotes sleep anticipation in the brain. When we are exposed to light, our melatonin levels are suppressed in the body. This suppression can lead to irregular sleep-wake cycles.

The second way that light affects our circadian clock is by shifting the circadian phase. A shift in the circadian phase means that your bedtime and wake-time could move earlier in the day or later in the day. Typically, morning light advances the circadian clock while evening and night light delays it. The latter can lead to irregular sleep-wake cycles and poor sleep.

So, why is the circadian rhythm so important? That’s because a lot of crucial biological processes are determined by it. These include your appetite, energy levels, hormone production, body temperature, cell regeneration, brain wave activity, and so on. These are all processes that are vital to life itself and happen automatically in the background without our conscious involvement. Also, as you can tell, without these processes one wouldn’t even be alive.

Understanding how your circadian rhythms work and how light influences them can help you optimize your sleep. It allows you to take steps and seek ways that you can incorporate in your daily routine to get better sleep. Let’s take a look at some of these ways.

To optimize your sleep, you may first need to take care of what you do in the morning after you wake up. It’s a good idea to expose yourself to light, preferably natural light, during the early hours. Natural light is preferred because it is full spectrum light (meaning that it has all the colors of the rainbow as well as other wavelengths like infrared and ultraviolet). So, when you’re exposed to natural light, there is an added bonus of generating vitamin D by your skin.

Studies have shown that people who receive higher levels of light in the morning experience better sleep quality, reduced sleep onset latency (the time it takes to fall asleep), and their circadian rhythms get better synchronized with the environment. When you expose yourself to bright light early in the morning, you signal to your brain that it’s time to suppress melatonin production. This decrease in melatonin levels then increases alertness and arousal. It has been shown that, for most people, it is better if they can be exposed to sunlight right after they wake up (typically within the first hour). So, you could head out into your balcony or your front yard and get some direct sunlight. It’s advisable to spend 30-45 minutes outside so that ample light can enter your eyes. Sunlight entering through your windows may not have the same effect. Also, it’s a good idea to not wear sunglasses as they may limit the amount of sunlight entering your eyes.

You could also expose yourself to artificial light if natural light is not available or going outside is not an option. You could use lamps for this purpose or use the HumanCharger like I do. It is a bright light therapy device, using which is similar to using earphones. You simply place them in your ears. It uses white light that passes through your ear canal and stimulates the photosensitive receptors of the brain.

I believe in this device because it is research-backed. The company conducted research from 2007 in collaboration with a team from the University of Oulu. They wanted to study the applications of transcranial bright light. This basically means administering bright light via the ear canals and through the skull. The researchers at the University of Oulu found that certain areas of the brain are sensitive to light. They also discovered that these brain areas can be reached by light through ear canals, ear tissues and bones of the skull. So, by using a device like the HumanCharger, you can stimulate the light-sensitive areas of the brain. As stated above, this is helpful when you can’t go outside in the morning. In fact, I use this device extensively during winter months.

Our circadian rhythms evolved in a world where it got pitch dark after the sunset. But now, we have artificial light and so, most of us are constantly exposed to lights from bulbs or screens even during the night. Since this type of light is a recent phenomenon, our circadian rhythms haven’t had enough time to adapt to it. So, bright artificial lights after the sunset can leave them confused. This can lower your sleep quality and cause irregular sleep cycles.

The main problem is that modern-day artificial lights have a lot of blue light (even though you might not notice it with your eyes). And, exposure to artificial light that is enriched with blue light can confuse the internal clock. This happens due to the suppression of melatonin in the body. In an experiment conducted by Harvard researchers, it was found that 6.5 hours of exposure to blue light can suppress melatonin levels for 3 hours compared to 1.5 hours of suppression when exposed to green light.

In order to avoid this, it’s a good idea to use blue light goggles. These types of goggles block the blue light coming from a source, decreasing the effect that artificial light has on our sleep patterns. I personally use the classic night swannies glasses from Swanwick. They block blue light from your surroundings from reaching your eyes. Also, when it comes to computers, phones, and tablets, you can use a blue light filter. Most devices these days come with this feature preinstalled.

You may have noticed that when you sleep in a pitch-black environment, you feel more relaxed and sleep better. As explained above, this happens due to our circadian rhythms. When it’s dark in the environment, our internal clock gets the signal that it’s time to rest. So, many people use sleep masks to block out light from reaching their eyes. But this might not be enough on its own.

A study was conducted in 1998 where researchers placed a small LED light, the size of a nickel, under the subjects’ knee. They found that even though the subject couldn’t see the light with their eyes, it still had an impact on their circadian rhythm. This shows that our skin may also have photoreceptors that are sending information to our brains, the nervous system, and internal organs about what time it is.

So, there is a need to eliminate as much light as possible from your surroundings. This will help you sleep in a pitch black environment which will, in turn, help you optimize your sleep at night. I personally do this through three main ways:

Red light can be quite beneficial in helping your body transition to its sleep cycle. Research has shown that exposure to red light (or infrared light) can lead to increased serum melatonin levels, better sleep, and improved muscle regeneration. Unlike blue light, red light is a low-energy and low-temperature light. So, it doesn’t disrupt sleep as blue light does.

It might help to gradually switch to red light after dusk. It could signal your internal biological clock to get ready for sleep. In fact, I do this personally and find that it helps me better transition to my natural sleep cycle. One way you could easily change to red light in your home is by using smart lamps that allow you to control the color and intensity of the light that they emit. You can control the color and intensity of the light using your smartphone. Sleeping with red lights switched on in your room might be very useful if you have to get up to pee at night. If you use the regular white-colored light, it could disrupt your sleep.

Reading books on electronic devices like iPads, Kindle, and smartphones has been gaining popularity for many years now. However, with this comes the increased risk of sleep disruption. Multiple research studies have shown that using electronic devices before going to bed has a negative impact on our sleep quality. The bright light from these e-readers can suppress the release of melatonin, decrease sleepiness, and reduce the time spent in REM sleep. Most of these devices emit blue light and that negatively affects the circadian rhythm of our bodies. So, if you have a habit of or if you want to read a book before going to bed, it’s a good idea to switch to printed books.

There is also another way that reading books on e-readers can affect your sleep quality. In one research study, it was found that screens can impact your brain activity. In the study, subjects were made to gaze at monitor screens and their brain waves were measured. It was discovered that their brains generated gamma waves while they were looking at the screens. The reason why this is important is that gamma brainwaves have the highest frequency among all our brain waves. Scientists say that they relate to simultaneous processing of information from different brain areas. So, when you read books on e-readers, these can cause your brain to go into a more active state which may cause sleep disruption.

So, now you might be more aware that light plays a crucial role in determining our sleep quality. To that effect, you can take the following actionable steps to better optimize your sleep:

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