Use your laptop, tablet, or iPhone at night? Electric lighting—particularly sophisticated devices with LED lighting—can seriously interfere with your sleep, said Charles Czeisler, a professor of sleep medicine at Harvard Medical School in an article in Saturday’s Huffington Post.
“Technology has effectively decoupled us from the natural 24-hour day to which our bodies evolved,” Czeisler wrote this month in the journal Nature, “driving us to go to bed later. And we use caffeine in the morning to rise as early as we ever did, putting the squeeze on sleep.”
For some years now, I’ve known that light suppresses melatonin, the hormone secreted by the pineal gland that helps us fall and stay asleep at night. So at 9 or 10 p.m., I walk around dimming all the lights in my house. I try to create a sleep-friendly environment that allows me to drop off at a reasonable hour.
But research in the past couple of years is showing that LED lighting, found in devices that connect us to the Internet, is particularly harmful to sleep when we’re exposed to it in the evening and at night.
What’s So Bad about LEDs?
The human eye is composed of cells that enable vision but also has cells whose sole purpose is to detect light. These cells contain melanopsin, which is extremely responsive to the blue and blue-green light found abundantly in daylight and in LEDs. Blue light striking these melanopsin-containing cells suppresses the secretion of melatonin and sends a message to the brain that it’s still daytime, making it harder to fall asleep.
But LED screens on phones and laptops are fairly small, so you might wonder how they could have the same effect on the brain as daylight. After all, TV screens also emit blue light, yet Americans have been nodding off to late-night movies and comedy shows for decades.
Proximity is the critical difference here, according to Harvard Medical School sleep researcher Steven Lockley, quoted last year in an article written for the McClatchy-Tribune News Service.
“The closer you have a light source to the face, the more intense it is,” said Lockley, co-author of Sleep: A Very Short Introduction, “And the further you go away, it falls off quite quickly. So having things [laptops, tablets, and iPhones] close to the face is much worse than having a TV that’s 10 feet away.”
Minor changes can help you avoid the harmful effects of blue and blue-green lighting at night:
- If devices have a “settings” feature, adjust the brightness of the screen and switch to the “white on black” mode in the evening
- Purchase an app that automatically lowers the color temperature on your computer screen at night
- Wear amber glasses that filter out blue light.
But the best solution is to turn all such devices off two hours before bedtime, when melatonin secretion normally begins. If you’re an insomniac like me, you’ll want to remove as many barriers to sound sleep as you can.
Do you use LED lighting and, if so, have you noticed it has an impact on your sleep?