Our Screens Are Killing Us

Before I get to the actual point of this post, I want to make a brief disclaimer. I’m not anti-modern technology. Technology, such as computers, phones, etc all have been tremendously beneficial in advancing the material standard of living of humans.

The marginal cost of accessing information and gaining knowledge has been dramatically reduced with the advent of modern forms of communication and screens. The main point of this post is to not talk about the material aspect, but rather the health aspect of modern technology. Technology is a tool, and like any tool, can be misused.

Now onto the post…

Visible light is the portion of the electromagnetic spectrum that is visible to the human eye. It ranges in wavelength from approximately 380 nanometers (violet) to 740 nanometers (red).

The visible light spectrum consists of the following colors, in order of decreasing frequency and increasing wavelength:

Violet — Shortest wavelengths, highest frequency. Wavelength range 380–450 nm.

Blue — Wavelength range 450–495 nm.

Green — Wavelength range 495–570 nm.

Yellow — Wavelength range 570–590 nm.

Orange — Wavelength range 590–620 nm.

Red — Longest wavelengths, lowest frequency. Wavelength range 620–740 nm.

The visible colors we see are determined by the different wavelengths of light. When all wavelengths are combined, white light is produced. The primary colors are red, green, and blue. Combining primary colors creates other visible colors. For example, red + blue makes magenta, and green + blue makes cyan.

When light passes through a prism, the different wavelengths separate into a rainbow spectrum because they refract at slightly different angles. This demonstrates that visible white light is actually a combination of the wavelengths corresponding to all the colors we can see.

Our eyes contain color receptor cells called cones that are sensitive to different wavelengths of light. This allows our visual system to detect the various colors. The visible light spectrum represents only a small portion of the entire electromagnetic spectrum, but it is the part crucial for human vision.

Humans (and all land-based animals) have for 99.9% of their existence been exposed to only sunlight, moonlight, and fire until the advent of Incandescent lighting in the late 19th century. Since then, humans have been exposed to blue light significantly more than what our ancestors went through.

Sunlight, depending on time of day, cloudiness, etc, is generally composed of 52–55% infrared light, 42–43% visible light, 3–5% ultraviolet light. Like I said, it’s highly dependent on time of day. During the morning and evening, sunlight is composed of more infrared, while UV will be relatively higher in proportion from 12:00–3:00 a.m.

I’m not going to get into the specifics of sunlight and the mechanisms in which each type of light/radiation interact with one another when our bodies are exposed to it, since it’s quite complex and deserving of its own post. My point so far has been to explain that these are the wavelengths of light that humans have evolved under for thousands of years and that only until recently did we invent the means to create artificial blue light in incredibly high and unnatural volume.

Since blue light (400–490nm) is increasingly used in devices like LEDs, TVs, and phones,

Blue light, especially at high intensities, can also damage the retina through oxidative stress:

Experimental evidence indicates that wavelengths in the blue part of the spectrum (400–490 nm) can induce damage in the retina, and although the initial damage following exposure to blue light may be confined to the RPE, a damaged RPE eventually leads to photoreceptor death. Although most studies on the effects of blue light have focused on the mechanisms responsible for the damage to the photoreceptors following an acute exposure to high intensity light, some studies have reported that sub-threshold exposure to blue light can also induce damage in photoreceptors

Not only does it damage the retina, but it also in skin cells. A mice study found that blue light exposure can induce oxidative stress in live mouse skin and human keratinocyte cells by producing reactive oxygen species (ROS), meanwhile exposure to other wavelengths of light did not:

Green light illumination (peak wavelength 523 nm) did not cause any significant change in mitochondrial roGFP redox state both at low and high illumination intensities (Fig. 1c,d,f). We also tested the red, far red and infrared light (Fig. 1e,f), but none of these longer wavelengths was able to induce oxidative stress in mitochondria (Nakashima et al. 11).

Blue Light also has destructive effects on circadian rhythms, which is our bodies natural internal body clock that regulates a whole bunch of various metabolic processes throughout a 24 hour cycle. Circadian is regulated by light exposure, primarily through photoreceptor proteins that send light signals to the hypothalamic suprachiasmatic nucleus. Exposure to bright light (and especially blue light) during dusk and night will reduce the production of melatonin (sleeping hormone), leading to a misaligned circadian and leaves the body at a significantly higher risk of developing various diseases.

A literature review published in the Journal Chronobiology International looked into both observational and experimental evidence on the topic and came the multiple conclusions.

• Observational studies show that higher outdoor artificial light at night (ALAN) levels (measured by satellite data) are associated with increased risk of breast and prostate cancer. Individual lighting habits during sleep, like keeping lights on in the bedroom, also show increased breast cancer risk.
• Experimental studies expose subjects to bright light vs dim light conditions at night in controlled settings. Bright light exposure suppresses melatonin secretion, increases sleep latency, alters body temperature rhythms, reduces alertness and performance. Bright blue light has stronger effects.
• Characteristics of light like intensity, wavelength, exposure duration and timing modulate the effects. Evening light exposure and longer duration have greater impacts on circadian disruption.
• Circadian disruption from ALAN can negatively impact psychological, cardiovascular, metabolic functions. It may increase risk of sleep disorders, obesity, diabetes, heart disease, mood disorders.

Another systematic review published in the same journal found similar results regarding Blue Light effect on melatonin suppression.

Endogenous (produced within the body) Melatonin is not only just a sleeping hormone, but also a potent antioxidant. Melatonin reverses skin damage caused by UV light, has numerous anti-cancer effects, etc. The diagram below is from Samanta (2020) which shows the mechanisms in which melatonin, which is endogenously produced from exposure to darkness, has numerous anti-cancer and anti-inflammatory effects:

Figure 5 Samanta (2020)

Basically, humans evolved for thousands of years under conditions that would maximize the production of endogenous melatonin due to exposure to broad-spectrum sunlight and dark nights. Nowadays, people in the developed world aren’t exposed to the various spectrums of light that the Sun emits, and instead are exposed to a highly unnatural proportion of Blue light from immediately after waking up all the way to bedtime.

The circadian “clocks” within our bodies are not only regulated by photoreceptors in the retina, but also by skin. It was recently discovered that that melanopsin, a light-absorbing protein, is not only concentrated in the retina, but also expressed in skin cells. Meaning that even exposing your skin to blue light during evening and night hours has harmful effects on circadian rhythms.

So, what are the solutions or ways to fix this problem? Well for one try to get as much sunlight as possible during morning and evening hours. Exposing yourself to sunlight during these hours is known to align your circadian with your local day/night cycle. The sun has a higher proportion of infrared light during sunset, and the natural blue light the sun emits during the sunrise is in combination with the infrared as well. See, blue light from the sun isn’t problematic like blue light from screens because it’s in proportion with other wavelengths of light that interact with another to provide stimulus to various processes within the body.

The next solution is too either put a 0 tolerance on screen usage during late evening hours and during the night. If you must utilize a device, put a red color filter on the screen and also use blue-light blocking glasses. Be careful though, since there are many companies that don’t sell blockers that don’t completely filter out all forms of blue light. A good sign that the blockers are for real is if they have a dark orange tinge to them like these ones:

Here is a TL;DR for those who don’t want to read the whole thing:

Modern devices like phones and screens expose us to high levels of blue light that are far greater than humans evolved under natural sunlight to handle. Sunlight contains a balance of wavelengths across the visible spectrum, while artificial lights are disproportionately rich in blue wavelengths.

According to studies linked previously, excessive blue light exposure can damage the retina and skin by generating oxidative stress. Blue light is especially disruptive at night, as it suppresses the production of melatonin. This hormone normally peaks at night and has antioxidant, anti-cancer, and anti-inflammatory benefits.

Disrupting the natural circadian rhythm governed by melatonin leads to serious health consequences. The studies linked circadian disruption to increased risks of several cancers, diabetes, cardiovascular disease, mood disorders, sleep disturbances, obesity, and more. It essentially throws our body’s metabolic processes that follow a daily cycle out of alignment if we are exposed to too much blue light at inappropriate times.

To mitigate the harms of artificial blue light, I recommend getting more sunlight exposure during the mornings/evenings to properly set circadian rhythm. Avoiding looking at screens at night allows melatonin levels to rise uninterrupted. Wearing blue light blocking glasses is also suggested, especially if nighttime screen use is unavoidable. Overall, being thoughtful about light exposure and timing can optimize health.

Thank you for reading!