In the study, researchers looked at what happened to fruit flies that were exposed to 12-hour stretches of blue LED light each day. The light damaged both eye cells and brain cells in the flies and impaired the flies' ability to move around their enclosures-and it also shortened their lives compared to other flies that lived in complete darkness or those that were exposed to light with blue filtered out. Even flies that were born without eyes were affected by the blue light, suggesting that it isn't necessary to see the light to be harmed by it.
The research started serendipitously, says Jaga Giebultowicz, a professor of integrated biology at Oregon State who studies biological clocks. "We thought that cycles of light and darkness were good for flies," she says. "And then we found that they live longer in constant darkness. So we got very interested in this, and then by looking at different light wavelengths, different colors, we found that blue was most detrimental." The blue light used in the lab is similar to the blue light that emanates from phones, computers, and other electronics.
If you don't feel like you have much in common with a fly, previous studies in humans have looked at short-term effects of blue light exposure. A Harvard study, for example, found that when people were exposed to several hours of blue light, it suppressed the production of melatonin, a hormone that regulates sleep, and shifted their circadian rhythms. A similar study at the University of Toronto found that when people wore glasses that blocked blue light, it had an impact on their melatonin levels. But no long-term, lifelong studies in humans have been conducted, in part because our attachment to gadgets that emit blue light is a relatively new phenomenon.
It would also be challenging to study the effects over a human lifespan, but the study of flies can give clues about potential long-term effects. "Flies are not humans, but the cells work the same," says Giebultowicz. After long-term exposure, the flies' cells started to show damage. "The genes that protect cells from stress are upregulated or very active in blue light," she says. "That means after 12 hours of blue light, they have high activity, which is telling us that the cells are under stress." If the flies are given a choice, they avoid blue light. The researchers are now continuing to study why the damage happens.
While there isn't proof yet that long exposure to blue light could shorten human lives, it might be worth adjusting your gadgets to turn down the brightness or physically blocking blue light with amber glasses or screen protectors, just in case. And it's one more reason to remind yourself to spend less time staring at screens.