Thanks to the boom in mobile technology — particularly smartphones and tablets — screens have become ubiquitous in modern society. It is almost impossible for most people to avoid exposing their eyes to some sort of screen for hours at a time, whether it is texting on your phone, bingeing shows and movies on Netflix, or playing video games.
In fact, the introduction of electricity is what first began the disruption of 3 billion years of cyclical sunlight governing the functions of life. What has been the effect of increasingly undermining this cycle, which humans have long been shaped by?
Wired explores some of the troubling research coming out regarding if and how more and more light exposure is negatively impacting us:
Researchers now know that increased nighttime light exposure tracks with increased rates of breast cancer, obesity and depression. Correlation isn’t causation, of course, and it’s easy to imagine all the ways researchers might mistake those findings. The easy availability of electric lighting almost certainly tracks with various disease-causing factors: bad diets, sedentary lifestyles, exposure to they array of chemicals that come along with modernity. Oil refineries and aluminum smelters, to be hyperbolic, also blaze with light at night.
Yet biology at least supports some of the correlations. The circadian system synchronizes physiological function—from digestion to body temperature, cell repair and immune system activity—with a 24-hour cycle of light and dark. Even photosynthetic bacteria thought to resemble Earth’s earliest life forms have circadian rhythms. Despite its ubiquity, though, scientists discovered only in the last decade what triggers circadian activity in mammals: specialized cells in the retina, the light-sensing part of the eye, rather than conveying visual detail from eye to brain, simply signal the presence or absence of light. Activity in these cells sets off a reaction that calibrates clocks in every cell and tissue in a body. Now, these cells are especially sensitive to blue wavelengths—like those in a daytime sky.
But artificial lights, particularly LCDs, some LEDs, and fluorescent bulbs, also favor the blue side of the spectrum. So even a brief exposure to dim artificial light can trick a night-subdued circadian system into behaving as though day has arrived. Circadian disruption in turn produces a wealth of downstream effects, including dysregulation of key hormones. “Circadian rhythm is being tied to so many important functions”, says Joseph Takahashi, a neurobiologist at the University of Texas Southwestern. “We’re just beginning to discover all the molecular pathways that this gene network regulates. It’s not just the sleep-wake cycle. There are system-wide, drastic changes”. His lab has found that tweaking a key circadian clock gene in mice gives them diabetes. And a tour-de-force 2009 study put human volunteers on a 28-hour day-night cycle, then measured what happened to their endocrine, metabolic and cardiovascular systems.
As the article later notes, it will take a lot more research to confirm the causation between disrupting the circadian rhythm and suffering a range of mental and physical problems. Anecdotal evidence would suggest that in the long-term, for many (though not all) people, too much exposure to screen-light can cause problems. But given the many other features of modern society that are just as culpable — long hours of work, constant overstimulation, sedentary living — identifying which, if not most, aspects of the 21st century lifestyle is responsible can be difficult to do, let alone resolve.