​How Blue Light From Screens Affects Your Health

Long ago, before artificial lights became the norm, our evenings were illuminated by the light of the candle or by kerosene lanterns. These days, we take our access to lighting for granted. But lights at night can throw our circadian rhythm — your body's biological clock — off kilter, causing problems with sleep that may contribute to a range of devastating diseases.

But not all types of light have the same effect on our health. Blue wavelengths, which include our TVs, phones, tablets, and computer screens, are particularly disruptive once the sun goes down. An experiment comparing the effects of exposure to blue and green light of similar brightness found that blue light suppressed melatonin, the hormone that governs our circadian rhythm, for around three hours, compared to 1.5 hours for green light. The blue light also shifted circadian rhythms by twice as much as the green light.

Here are three important ways in which blue light affects your overall health — and what you can do to reduce the risk.

1. An increased risk of cancer. A large body of research has found a link between working the night shift — and the exposure to light it promotes — and breast and prostate cancer. Scientists believe that this may be due to the fact that when we're exposed to light, our bodies secrete less melatonin. Some preliminary evidence suggests that suppressed melatonin may contribute to some cancers as well as other diseases.
2. Increased diabetes and obesity. In a study by Harvard University, researchers put participants on a schedule that gradually changed the timing of their circadian rhythms. As a result, the participants' blood sugar increased, putting them in a pre-diabetic state. Additionally, levels of the hormone leptin, which governs feeling full after eating, were reduced. This may contribute to obesity and diabetes, according to the researchers.
3. Sleep problems. According to Harvard, even dim light can reduce melatonin production and interfere with the body's circadian rhythm. But blue light in particular is far more powerful than other types of light at reducing melatonin production, as one recent University of Toronto study found. In the study, researchers compared the melatonin levels of two groups. The first group was exposed to regular dim indoor light, while the second group wore blue-light-blocking goggles while exposed to bright indoor light. The levels of melatonin were about the same in both groups, shoring up the hypothesis that blue light is a powerful melatonin suppressor and interferes with healthy sleep, which can contribute to a suppressed immune system and the development of a number of diseases, including heart disease and diabetes.

What You Can Do

There are several ways you can reduce your exposure to blue light at night for better health:

• Switch out your blue nightlight bulbs for red bulbs, which interfere the least with melatonin production and the circadian rhythm.
• Two hours before bed, turn off your screens, and read a book instead.
• If you must watch TV or use electronic devices at night, consider wearing glasses that block blue light, or install an app on your devices that filters out the blue wavelength.
• During the day, bask in as much bright light as possible. This will boost your ability to fall asleep and stay asleep at night, and it'll also improve your alertness and mood throughout the day.
• Don't be tempted to get on your device at night when you wake up and can't fall back asleep. Instead, get up and sit quietly in a dim or dark room until you feel sleepy again.

If you're suffering from insomnia, reducing your exposure to blue light at night can help improve your sleep. Even if you sleep just fine despite being glued to your screen at night, cutting out blue light exposure may reduce your risk of disease and improve the function of your circadian rhythm.