The increasing use of smartphones, tablets, and e-readers continues to be cause for concern among scientific experts. In 2014, the Pew Research Center found 90 percent of Americans own a cell phone; 58 percent own a smartphone; 32 percent own an e-reader; and 42 percent own a tablet computer — all perhaps without knowing the toll it takes on human biology.

Richard Stevens, an epidemiologist working out of the University of Connecticut Health Center, has been studying the effects of mobile technology’s blue light for three decades. While he, too, has found the blue light that emitted from these devices inhibits sleep and work performance, he recently found there may be a chance to correct the situation. That is to say the typical lighting that’s affecting human biology can be improved.

“We're learning that better lighting can reduce these physiological effects,” Stevens said in a press release. “By that, we mean dimmer and longer wavelengths in the evening, and avoiding the bright blue of e-readers, tablets, and smart phones."

It may not seem like it, but when using mobile technology into the night, enough blue light is emitted to suppress the sleep hormone melatonin. In turn, this throws off the body’s circadian rhythm, which is the biological mechanism responsible for restful sleep. Separate research has shown the circadian rhythm can set the pace for a healthy heart and weight, plus a healthy liver. So it might be better to reach for, say, a paper book over an e-reader when trying to fall asleep.

“The physiological effects of light at night and sleep disruption have been ‘proven’ in the sense that there is general acceptance in the scientific community of its truth. … What has not been ‘proven’ is that electric light-at-night causally increases risk of cancer, obesity, diabetes, and/or depression,” Stevens and his co-author wrote in their recent paper.

Blue light, however, isn’t solely to blame for messing with the body’s internal clock. The authors added there’s also “inadequate light during the day inside buildings for a robust resetting of the human endogenous circadian rhythmicity.” Over the past 50 years, use of electric light for work and domestic life has significantly grown, lessening the amount of time people spend in natural, vitamin D-rich sunlight.

One small study done in 2013 took eight people with varied chronotypes — think of morning birds and night owls — and sent them camping in Colorado (where they lived). Despite participants' initial range of bedtimes, researchers found there was far less variability among them toward the end of the study. 

It’s the fact we’re less exposed to natural light during the day and overexposed to blue light at night that’s impacting our biology. Researchers find balancing this out “may help to reduce the physiological, cognitive, and health consequences of circadian disruption.” Again, this might mean a paper book instead of an e-reader at night and incandescent bulbs during the day. These bulbs, Stevens said, are dimmer and more circadian friendly.

Source: Stevens R.G. and Zhu Y. Electric light, particularly at night, disrupts human circadian rhythmicity: is that a problem? Philosophical Transactions of the Royal Society B, 2015.