We're Constantly Bathed in Artificial Light -- Is it Wreaking Havoc on Our Health?
Photo Credit: Andresr/Shutterstock.com
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If you live in the developed world, darkness can be hard to find. Our plugged-in, 24-7 lifestyles deliver a barrage of not just technology, but also light. All the time. And this may have negative health consequences that scientists are only just beginning to understand.
We are a diurnal species, which means we are genetically programmed to do our work during the day when it’s light out, and sleep when it’s dark. For many thousands of generations as hunter/gathers we did just that, with the only light after dark coming from the moon, stars or firelight. With the industrial revolution and the invention of electric light, all that changed.
We went from incandescent electric light to fluorescents and neon. Now we are increasing our use of solid-state lighting, such as LEDs (light-emitting diodes).
“There is a tremendous energy savings to be realized as you replace incandescent and fluorescent light sources with LEDs, but then the question is what are the health concerns,” said George Brainard, a professor at Thomas Jefferson University’s Jefferson Medical College and director of its Light Research Program.
We already know there are health impacts from light. For starters, light can be used therapeutically; the most well-known cases are the treatment of winter depression or seasonal affective disorder.
“Lighting stimulus is neither good or bad, it’s how it’s used, what it’s used for and when it is used,” said Brainard. “But just like a drug, any drug that can heal, can also cause harm. If light has the capacity to invoke a therapeutic benefit, it also has the flip side: it can have unwanted side effects when used inappropriately.”
To understand how light impacts our health, you have to understand a little about how the eye works. “The eye mediates two different effects of light,” said Alfred J. Lewy of Oregon Health and Science University. “One effect of course is vision—any of the visible wavelengths hitting rods or cones mediates the vision.”
But the other effect has to do with another part of our visual system that operates below our level of consciousness—these are photoreceptors in our eyes that regulate biology and behavior. “More specifically, the circadian system, our biological rhythms, our neuroendocrine system (that’s hormonal), and neurobehavioral responses,” said Brainard.
Scientists learned that bright light could suppress the production of the hormone melatonin (which helps regulate our circadian rhythms). They learned that this photoreceptor system is especially sensitive to shorter wavelengths, which is light that appears blue to us.
This discovery tweaked how light therapy could be done. Instead of blasting patients with high-intensity light from the entire spectrum, they could use less intense light that came from the part of the spectrum we are most sensitive to: blue light. It was a therapeutic win.
But what happens if we are subjected to light at night, particularly light that contains a lot of blue to which we are most sensitive? We already know that despite being diurnal creatures we don’t go to sleep the moment it gets dark. When the sun sets, we turn on the lights, and we often also turn on other devices like TVs, computers, tablets, and electronic readers.
“What if that light is enriched with blue wavelengths that are sending a signal to your circadian system, your neuroendocrine system, that it is full-bore daytime and you want your body in top alertness?” asked Brainard. “When you shut off lights to go to sleep in the evening, is it going to delay and possibly disrupt sleep during the night?”
The answer is… we’re still trying to figure that out. The scientific “literature is young,” says Brainard.