Over the past couple centuries, artificial light has gradually become ubiquitous in our environment. Modern humans are constantly exposed to artificial light emitted by smartphones, lightbulbs, computers, and other technology. It’s easy to forget that these light-emitting devices are extremely novel additions to our habitat; for 99 percent of our evolutionary history, we had no exposure to artificial light, regardless of its provenance. This therefore highlights our genetic maladaptation to environments that are saturated with artificial light.
What Are the Consequences of Living in a World of Incomplete Darkness?
Our pre-industrial ancestors didn’t have any lamps to help keep darkness at bay after sunset. Nor could they chat with friends on Facebook messenger until late at night, or hammer out last-minute work on a computer right before they hit the sack. They made do with natural light emitted by the sun. They could also light bonfires or (more recently) candles; however, they obviously lacked access to the myriad devices that we contemporary humans use to illuminate our surroundings.
This figures importantly in the increasing prevalence of sleep-related disorders today. Not only are conditions such as insomnia fairly common these days, but many contemporary people rarely, if ever, get a truly good night’s sleep. Many people are groggy and tired in the morning, relying on caffeine and/or sugar intake throughout the day to prop up their energy levels. One could argue that they’re never completely awake, nor completely asleep. They do sleep—but such sleep is of poor quality, in large part because they inhabit an environment filled with sleep-disrupting agents: smartphones, computers, streetlights, and highly processed, sugary foods.
Lamps, computers, and smartphones have the potential to severely disrupt the quality of one’s sleep, as well as other aspects of one’s life. Exposure to artificial bright light during the nighttime is particularly damaging in that it suppresses melatonin secretion, increases sleep-onset latency, and increases alertness.1, 3, 5
This circadian misalignment may in turn have negative effects on psychological, cardiovascular, and metabolic function and can increase one’s risk of developing several types of chronic diseases, including breast cancer.1, 3, 5
Virtually every part of our physiology is affected by the quality and duration of our sleep. If you don’t sleep well, you may experience cravings for unhealthy food, feel mentally drained, and have trouble keeping your energy levels up throughout the day.
Some Light-Emitting Devices are More Destructive Than Others
Artificial light, regardless of its origin, can impair the quality of our sleep. That said, some forms of artificial light are particularly detrimental. Computers, smartphones, e-readers, and similar devices have the potential to turn what would otherwise have been a good night’s sleep into a nightmare. Not only do these devices emit blue-wavelength light that is particularly effective at suppressing melatonin production,2, 4, 6 but they also light up our brains, given that they are sources of endless information and stimuli (stressors). In essence, they keep our brains engaged and signal that it’s time to work, not to sleep.
Why Aren’t the Sleep-Disrupting Properties of Artificial Light More Widely Known?
When I was younger, I remember being largely unconcerned about the effects of regular artificial-light exposure on my body. I often used my smartphone late at night while lying in bed. I didn’t turn off the lamps in my room until right before I headed to bed. I didn’t see any need to incorporate sleep-optimization strategies in my routine.
Many people seem to operate in a similar manner as I did back then.
It seems that not many people know that artificial lighting has the potential to severely impair their sleep quality. They lie in bed at night, surfing or chatting with friends on their smartphones, and give little thought to how all their daily artificial-light exposure affects their melatonin production and circadian rhythm.
It’s not really surprising that these beliefs and practices are so common; the perils of artificial light exposure have garnered some recognition, but are still largely ignored in the wider culture. The scenario would probably be very different if evolutionary health theories were given more credence in our society. If more health authorities acknowledged our bodies’ lack of adaptation to a hyper-illuminated world, the public might approach artificial lighting with much more care and consideration.
Our brains, internal biological clocks, and hormonal systems were designed to function optimally in a very different environment from that which we currently inhabit. Sleep optimization is a critical component of a physiologically appropriate lifestyle. One of the most important steps we can take to sleep more, and more deeply is to limit our use of light-emitting devices, particularly late at night.
1. Bedrosian TA, Nelson RJ. “Timing of Light Exposure Affects Mood and Brain Circuits.” Transl Psychiatry 7.1 (2017): e1017.
2. Chang AM, Aeschbach D, Duffy JF, Czeisler CA. “Evening Use of Light-Emitting E-readers Negatively Affects Sleep, Circadian Timing, and Next-Morning Alertness.” Proc Natl Acad Sci USA 112.4 (2015 Jan 27): 1232-7.
3. Cho Y, Ryu SH, Lee BR, Kim KH, Lee E, Choi J. “Effects of Artificial Light at Night on Human Health: A Literature Review of Observational and Experimental Studies Applied to Exposure Assessment.” Chronobiol Int 32.9 (2015): 1294-310.
4. Figueiro MG, Wood B, Plitnick B, Rea MS. “The Impact of Light from Computer Monitors on Melatonin Levels in College Students.” Neuro Endocrinol Lett 32 (2011): 158-63.
5. Haim A, Zubidat AE. “Artificial Light at Night: Melatonin as a Mediator between the Environment and Epigenome.” Philos Trans R Soc Lond B Biol Sci 370.1667 (2015 May 5): 20140121.
6. Wood B, Rea MS, Plitnick B, Figueiro MG. “Light Level and Duration of Exposure Determine the Impact of Self-Luminous Tablets on Melatonin Suppression.” Appl Ergon 44.2 (2013 March): 237-40.