The blue light from personal electronic devices has also been linked to serious physical and mental health problems.
Blue light is part of the full light spectrum, which means we're exposed to it by the sun every day. However, nighttime exposure to that light, which is emitted at high levels by smartphones, tablets, laptops, and other LED screens, may be damaging your vision. It also suppresses production of the hormone melatonin, which throws off your body's natural sleep cues.
When your melatonin levels and sleep cycle go haywire, your risk goes up for a wide range of ailments, from depression to cancer.
Our various personal electronic devices emit blue light because it's so bright. That's the only way we can see those screens when the sun is shining. But we've started to have regular close-up nighttime exposure to this light only in the past 10 or 20 years, as a recent Gigaom story on the topic notes.
Now we're really starting to see the consequences.
1. The damage that this habit does to our eyes alone is both significant and surprising. Direct exposure to blue light can cause damage to the retina. The American Macular Degeneration Foundation warns that retinal damage caused by blue light may lead to macular degeneration, which causes the loss of central vision — the ability to see what's in front of you.
It should be noted however, that most studies show this effect with the light being held very close to the retina, which may not exactly replicate typical phone use.
2. There may also be a link between cataracts and blue light, though more research is needed. Gigaom cited an eye doctor who says he's starting to see 35-year-olds with eyes that are as cloudy with cataracts as 75-year-olds. Though a single account can't prove that blue light exposure causes cataracts — this doctor just thinks there's a link, which doesn't count as evidence — the idea is being investigated. Still, studies haven't concluded anything certain yet.
3. Exposure to blue light at night can ruin sleep. Bright blue light disrupts the brain's production of melatonin, a hormone that helps regulate the sleep cycle. That's fine in the morning, but our brains are supposed to start producing melatonin when we are ready for sleep, and blue light interferes with that process. That's why smartphones ruin sleep, and messing with your sleep has a long list of associated health consequences that range from obesity to genetic disruption and memory problems.
4. Sleep disturbance and "light at night" have been linked to higher cancer risk, particularly for breast and prostate cancers. In addition to helping us sleep, melatonin also functions as an antioxidant. And while more research is needed, researchers have pointed to "uninterrupted darkness" as potentially protective against cancer. People whose natural melatonin production is suppressed are at a higher risk for a variety of cancers, though a causal relationship has not been found.
5. Blue light may also take a toll on mental health. Research also shows that people whose melatonin levels are suppressed and whose body clocks are thrown off by light exposure are more prone to depression.
Despite the way this may sound, it doesn't mean that blue light is bad all the time. At times, it's actually beneficial to your health.
Light tells us when to wake and when to sleep. When bright blue light sends a signal to the brain to stop producing melatonin, it also primes your brain to start production of the hormone again later — in theory while you are getting ready for bed.
Experts say that getting an hour of sunlight in the morning helps people regulate their melatonin production and sleep cycle. They recommend getting some morning light without wearing sunglasses, so light gets through the retina and reaches the pineal gland, which is what actually controls melatonin production.
That's great in the A.M., but when nighttime screen usage convinces our brains that it's morning and they shouldn't produce melatonin, that starts to wreak havoc on our bodies.
We can't avoid smartphones, computers, and tablets all the time. But we should try to limit our exposure at night. Sometimes, wearing amber glasses that block blue light or using apps that limit the amount of blue light coming from our screens may help.
Taking breaks from screentime is a good idea too – especially right before and in bed.