How does artificial light harm your health? (SQ-139)
Exposure to natural light is very important in keeping us healthy, active and alert. Spending a few minutes in the sun after you wake up sets you up for an energetic start. It regulates your sleep-wake cycle, improves mood and fills you with the much-needed burst of energy to tackle your day. As we all know, our body makes vitamin D when exposed to sunlight and Vitamin D plays an integral role in keeping your bones, immunity and heart in good health.
In fact, studies show that not getting enough sunlight affects eye health in children and young teens, increasing the risk of myopia or near-sightedness. 
While it is healthy to bask in little sunshine, exposure to artificial lights, especially at night, comes with its share of health risks. Before the arrival of artificial light, the sun was our cue to wake up or sleep. But today, with innumerable sources of artificial lighting at our disposal, we are continuously being exposed to artificial light at all times of the day.
There is mounting evidence that artificial light at night can affect your health in many ways. One of the most important aspects of our health affected by ill-timed use of artificial lights is sleep. And unhealthy sleeping patterns are independent risk factors in many chronic ailments including stress, depression, anxiety, obesity, diabetes, heart disease and low immunity.
In addition, artificial light also increases the risk of these serious health conditions through changes in circadian rhythms and reduced production of melatonin, a hormone that is associated with many health benefits.
But how does artificial light affect your health? Let’s explore this after a quick run-down on circadian rhythm and how it is directly affected by exposure to ill-timed artificial night.
Artificial light and circadian rhythm
The term circadian literally translates into “about day”, as in Latin ‘circa’ means around and ‘diem’ means day.
Circadian rhythms are patterns or activities that your body goes through across a period of 24-hour cycle. These cyclic patterns are responsible for many physical, mental and behavioral shifts that take place in our body.
Circadian rhythms influence many important processes such as secretion of hormones at appropriate times, appetite, digestion process, body temperature, sleep-wake patterns, alertness and immune function.
These rhythms are just one of the many in-built biological clocks that your body follows. And all these biological clocks are attuned to a master clock present in the hypothalamus, a part of the brain responsible for sleep, mood, behaviour, memory and cognition. This master clock, also known as SCN, receives direct input from the eyes.
Environmental factors can throw off your circadian rhythms. In fact, light is the major outside factor that controls circadian patterns. Light aligns your body’s internal circadian rhythm with the earth’s 24-hour cycle of day and night.
When your eyes sense light, they pass this information to the master clock in the brain, which uses this information to determine the time of the day, depending on the intensity of the light. The brain then refreshes internal processes, such as release of hormones, inducing feeling such alertness or sleepiness, digestion and hunger, to function accordingly.
A very well-known example of this process is the production of the hormone melatonin. As your eyes register darkness, the brain triggers the production of melatonin, a hormone that induces sleep.
“Your body is governed by in-built biological clocks and circadian rhythms – time dependent changes in body and brain. Sunlight and darkness play an important role in synchronizing these changes.”
Artificial light and its effects on your health
In today’s world, we are continuously being exposed to artificial lights after sundown. This exposure to artificial lights just before and at sleeping hours can disrupt your circadian rhythm and can even lead to health conditions such as insomnia, obesity, metabolic disorders, depression and seasonal affective disorder (SAD).  Studies show artificial light can also cause cancer.
And it has been found that blue light is most disruptive to health and sleeping patterns. Not all blue light is bad. In fact, most of the blue light comes from the sun. Sunlight consists of UV light rays and visible light rays, which come in varying wavelength, energy and colors (red, orange, yellow, green and blue). Blue light has health benefits as it boosts wakefulness, and also improves mood, memory, performance, mental sharpness and reaction times.
Incandescent lightbulbs, energy efficient LED bulbs, and fluorescent lighting at offices are some of the sources of artificial blue light. But experts are worried about the health effects of blue light emitted from the screens of electronic and digital devices, such as TVs, mobile phones, tablets, computers and laptops.
“Artificial lights at night can knock off your circadian rhythms, causing a range of health problems including sleep disruption, obesity, metabolic syndrome, hormonal dysfunction, depression and even cancer”.
Sleep disruption and melatonin suppression
Sunset and the accompanying darkness are the cues for the body to slow down and prepare to sleep. This is when your brain triggers the production of melatonin, a hormone released by the pineal gland. Melatonin levels are lowest during the day and your body starts producing it just hours before your sleeping time.
Over-exposure to artificial blue light, just hours before sleeping and at night can mess up with the production of melatonin, resulting in unwanted wakefulness and sleep disruption.
While all lights supress melatonin, studies show that light at the blue end of the spectrum (with shorter wavelength) has the most profound impact on melatonin production. Your eyes are not very good at blocking the blue light, whether natural blue light from the sun or man-made blue light. Pigments in your eyes – responsible for assessing the intensity of the light – are especially sensitive to the light with shorter wavelength.
So, when you experience light around bedtime, this tricks your brain into thinking it’s not yet time to sleep or prepare to sleep.
Melatonin suppression not only affects sleep but also creates havoc on mood, learning and memory. While melatonin is mostly associated with sleep, it also works as an antioxidant and protects the tissues from daily wear and tear.
“Melatonin is a hormone that promotes healthy sleep. Darkness triggers melatonin production, whereas exposure to light at night supresses melatonin. This causes sleep disruption and low sleep quality.”
Digital eye strain
Continuous use of digital devices for extended periods causes eyes and vision problems, also known as digital eye strain. It is because blue light has a very short wavelength and high energy, which makes it flicker and scatter more easily than other visible light in the spectrum.
In addition, studies show that people who use digital devices for extended periods of time, blink less. Reduced or incomplete blinking means reduced moisture, leading to dryness of eyes. It can also cause burning or itching of the eyes.
Constant near work impairs the ability of eyes to relax and focus at different distances, leading to blurred or double vision, near-sightedness, eye fatigue and other vision problems. Prolonged use of these devices also causes headaches, facial muscle fatigue and pain in neck, shoulders and back.
Early research suggests that overexposure to blue light may cause permanent eye damage. It can harm cells in the cornea, lens and retina, and may contribute towards the development of cataracts and age related macular degeneration. While more research is needed, the potential of the blue light damage to different structures of the eyes can’t be ignored. 
The fact is your eyes can effectively block the UV rays of the sun. The cornea and lens can stop the UV rays from reaching the retina, present in the back of the eye. The retina is very sensitive to light. But these structures aren’t very effective at blocking the blue light from reaching the retina.
Other visible lights with warmer tones, like red, have longer wavelength but blue light is remarkably similar to UV rays in terms of wavelength and energy. Since UV rays are known to cause retinal damage, blue light is a potential cause of concern, especially when it comes to eye health.
What’s alarming is that people are using digital devices for many hours every day. And the use of devices has increased significantly during the coronavirus pandemic.  Whether it is for office work, online classes, gaming, shopping or connecting on social media, people are using blue-light emitting devices at an unprecedented rate. These devices are not only used for long hours but are also kept very close to the face.
“Artificial light emitting from digital and electronic devices can cause digital eye strain, with symptoms such as tired and dry eyes, blurred vision, burning and itching of eyes, headache and pain in neck and back. Some early studies suggests that blue light can cause irreversible damage to the eyes, although more proof is needed”.
Metabolic syndrome and obesity
Long term exposure to artificial lights especially at night can derail your body’s in-built circadian rhythms. And this can have an adverse effect on your metabolic health too.
Research suggests that disruption in circadian rhythms, sleep deficiency and reduced production of melatonin can contribute to weight gain, obesity and metabolic syndrome. 
Poor sleep disrupts the hormones that regulate appetite and may cause weight gain through this mechanism. In addition, research shows that both acute and long-term exposure to light at night have been found to impact glucose metabolism and are associated with the development of overweight, obesity, and cardiovascular disease. 
This study also hints at a direct link between unnatural light exposure at night and metabolic syndrome, which appears to be related to circadian disruptions.  In addition, the findings also showed that greater exposure to daylight reduced the risk of metabolic syndrome.
Many other studies also indicate that prolonged exposure to artificial lights can have serious long-term implications on metabolic functions, fertility, heart health and cognition. 
“Melatonin and circadian disturbances created by artificial lights can cause metabolic syndrome, obesity and weight gain.”
The latest research reveals that people exposed to artificial lights at night may have an increased risk of developing thyroid cancer.  The study draws on the earlier findings that over-exposure to night-time light increases the risk of breast cancer.
Circadian rhythms play an integral role in regulating thyroid function. And considering that breast cancer and thyroid cancer have common roots in obesity and hormonal disruptions, the researchers predicted there may be a link between artificial light exposure at night and thyroid cancer risk.
In fact, a large number of studies show that there is a link between artificial light at night and cancer, including the cancer of lung, breast, colorectal, and prostate. [10-12]
This may be due to the disruption of the circadian system and melatonin suppression. Melatonin inhibits hormones that may play a role in cancer development.
“Research suggests that exposure to bright artificial lights can elevate the risk of thyroid cancer, breast cancer and many other types of cancer”
Effects of artificial lights on our ecosystem
The harmful effects of artificial lights are not limited to human beings. Insects, birds, amphibians and nocturnal animals are also affected by the glare from artificial lights. For example, light can disorient migratory birds or birds that hunt at night.
Light pollution also impacts sea turtles, who hatch at night on the shore. Bright artificial lights cause them to wander away from the ocean, forcing them to nest at less than conducive environments. In addition, bright lights from nearshore buildings also draw hatchlings towards land. So instead of going to moonlit ocean, they crawl inland, where they are likely to die of dehydration and exhaustion.
How can you reduce the impact of artificial lights?
- Keep away your phone and other digital devices two to three hours before bedtime
- Use dim red lights at night, if required.
- Switch off unnecessary indoor and outdoor lighting, at home and office buildings
- Turn off unnecessary lighting during daytime, at every given chance
- Install outdoor lights with anti-glare features
- Installation of motion sensors, to minimize use of artificial lights outdoors
- Use glow stones
- Buy IDA (https://www.darksky.org/) approved light fixtures
- Increase your exposure to sunlight, which is likely to maintain your sleep-wake cycle and help you sleep better at night
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2. Circadian Rhythms. National Institute of General Medical Sciences.
3. Fayiqa Ahamed Bahkir and Srinivasan Subramanian Grandee. Impact of the COVID-19 lockdown on digital device-related ocular health. Indian J Ophthalmol. 2020
4. Zhao et al. Research progress about the effect and prevention of blue light on eyes. Int J Ophthalmol. 2018.
5. AA Benedito-Silva et al. Association between light exposure and metabolic syndrome in a rural Brazilian town. PLoS One. 2020.
6. Reiter et al. Obesity and metabolic syndrome: association with chronodisruption, sleep deprivation, and melatonin suppression. Ann Med. 2012
7. Fleury et al. Metabolic Implications of Exposure to Light at Night: Lessons from Animal and Human Studies. Obesity. 2020.
8. Falcon et al. Exposure to Artificial Light at Night and the Consequences for Flora, Fauna, and Ecosystems. Frontiers. 2020.
9. Zhang et al. Associations between artificial light at night and risk for thyroid cancer: A large US cohort study. ACS Journals. 2021.
10. Redhwan A. Al-Naggar and Shirin Anil. Artificial Light at Night and Cancer: Global Study. Asian Pac J Cancer Prev. 2016
11. Garcia-Saenz et al. Evaluating the Association between Artificial Light-at-Night Exposure and Breast and Prostate Cancer Risk in Spain (MCC-Spain Study). Environ Health Perspect. 2018
12. Redhwan Al-Naggar and Lutfi Al-Maktari. Artificial Light at Night and Breast Cancer. IntechOpen. 2021.