Using screens safely at night

Using screens at night adversely affects sleep, but there are some things you can do to help protect your eyes.

Click here to read about a new study, published in PNAS, that measures the sleep impact of reading an iPad before bed.

Adjusting your screen:

• Learn how to adjust your device’s brightness, and dim it as far as possible at night.
• Most phones and tablets can invert colors, displaying white text on a black background. If you use a backlit device to read at night, learn how to change this setting. It’s a good way to reduce the light coming from your phone.
• If you’re using a desktop or laptop, your screen is likely larger and more alerting than an iPad. Unfortunately, at the moment Bedim is only available for iPhones and iPads. If you can’t use Bedim, try to plan your computer time earlier in the day so you can spend a couple hours winding down before bed.
• How close you hold your device affects brightness. A screen held 6 inches away exposes you to about 4 times more alerting light as one held 12 inches away - and that’s still too close.

Adjusting your habits:

Surprisingly short exposures of bright light can have alerting effects, so avoid bright light for an hour or two before bed.

• This also means: no peeking at your phone when you should be sleeping.
• Set your circadian clock by seeing some natural light each day. Even sitting near a window or being outdoors on a cloudy day is usually brighter than daytime artificial lighting indoors.
• Orange glasses can be used to block alerting light. However, “blue-blocking” coatings and lenses that look yellow are designed to block UV and this will not help with circadian timing. You’ll know it’s the right color if you put them on and say, “Wow, that’s too orange.”
• Bright lighting in your house also alerts your body. Use dimmers if you have them, or turn off brighter lights before bed.
• Dimming your lights actually helps twice, because it will make you more comfortable dimming your screen.
• If you have kids: Children require more sleep and are significantly more sensitive to blue light than adults, so these effects may be significantly greater for younger eyes.

PNAS study: using iPad before bed has major impact on sleep

A study published in PNAS shows that reading a backlit device before bed makes your sleep measurably worse than reading a paper book under dim light.

According to the study:

• While people are using an iPad at night their body produces 55% less melatonin
• After shutting off the lights (and the iPad), they took an extra 10 minutes to fall asleep
• When they did fall asleep, they had less REM sleep during the night
• The next morning, the iPad readers felt sleepier, and it took them “hours longer” to feel alert. The book readers quickly felt more alert immediately upon waking.
• When it was time for bed the next night, the iPad readers’ circadian clocks were delayed by more than 90 minutes. Their bodies began to feel tired an hour and a half later than normal, because they were exposed to alerting light from the iPad the night before.

Each participant was tested with both the iPad and reading a book. Books on paper did not suppress melatonin or cause participants to feel groggy the next day. The 5-day study was conducted by Anne-Marie Chang, Daniel Aeschbach, Jeanne F. Duffy, and Charles A. Czeisler at Brigham and Women’s Hospital (a Harvard Medical School teaching hospital).

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Bedim’s Take

This study shows that the bright blue light from displays at night is impacting our sleep. If you stay up late reading a bright iPad until just before bedtime, your sleep will be negatively affected, and your body will expect to stay up later the next night (as much as 90 minutes later). You may have trouble winding down, feeling alert when you should be getting tired. This level of melatonin suppression is quite large. Melatonin is known as the sleep hormone, and has many functions in the body related to sleep. It is also a strong anti-inflammatory known to suppress cancer cell growth. Because the circadian shift of using an iPad at night is very large, only a few nights of staying up late reading might put your body several hours out of phase with your normal routine.