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Although it is environmentally friendly, blue light can affect your sleep and potentially cause disease. Until the advent of artificial lighting, the sun was the major source of lighting, and people spent their evenings in (relative) darkness. Now, in much of the world, evenings are illuminated, and we take our easy access to all those lumens pretty much for granted.
There’s a lot of evidence that blue light, emitted by smartphones, tablets, laptops, and many other electronic devices, is impacting on the quantity and quality of the sleep we are getting. Darkness is a natural cue to our bodies that it’s time for sleep, but we’re circumventing it by staring at bright screens for hours after the sun has gone down.
Not all colors of light have the same effect. Blue wavelengths—which are beneficial during daylight hours because they boost attention, reaction times, and mood—seem to be the most disruptive at night. And the proliferation of electronics with screens, as well as energy-efficient lighting, is increasing our exposure to blue wavelengths, especially after sundown.
At night, light throws the body’s biological clock—the circadian rhythm—out of whack. Sleep suffers. Worse, research shows that it may contribute to the causation of cancer, diabetes, heart disease, and obesity.
Blue light tells our brain that it isn’t time to sleep, according to the experts.
“There are about 30,000 cells inside your eye that are reactive to the wavelength of light which would be considered blue,” explains clinical psychologist and sleep therapist, Dr. Michael J. Breus.
The impact of blue light has been well-known to sleep researchers and scientists for many years now. Blue light therapy is frequently used to shift sleep patterns and tackle sleep disorders.
Some studies suggest a link between exposure to light at night, such as working the night shift, to some types of cancer, diabetes, heart disease, and obesity. That’s not proof that nighttime light exposure causes these conditions; nor is it clear why it could be bad for us.
A Harvard study shed a little bit of light on the possible connection to diabetes and possibly obesity. The researchers put 10 people on a schedule that gradually shifted the timing of their circadian rhythms. Their blood sugar levels increased, throwing them into a prediabetic state, and levels of leptin, a hormone that leaves people feeling full after a meal, went down.
Even dim light can interfere with a person’s circadian rhythm and melatonin secretion. A mere eight lux—a level of brightness exceeded by most table lamps and about twice that of a night light—has an effect, notes Stephen Lockley, a Harvard sleep researcher.
Protect yourself from blue light at night
“There’s nothing wrong with blue light for most of the day,” says Dr. Breus. “You just don’t want to have it about 90 minutes or so before bed.”
- Use dim red lights for night lights. Red light has the least power to shift circadian rhythm and suppress melatonin.
- Avoid looking at bright screens beginning two to three hours before bed.
- If you work a night shift or use a lot of electronic devices at night, consider wearing blue-blocking glasses or installing an app that filters the blue/green wavelength at night.
- Expose yourself to lots of bright light during the day, which will boost your ability to sleep at night, as well as your mood and alertness during daylight.