Who owns a tablet and doesn’t do this? If you’re me, it involves reading a book on your iPad before you nod off. Ok, so I’m watching Netflix. Don’t judge. I’m not sure we need science to tell us this, but staring at the tablet or e-reader till 1am is bad for your sleep cycle.

According to a Harvard study, published in the Proceedings of the National Academy of Sciences, it’s all about the light. Anne-Marie Chang, lead researcher and neuroscientist in the Division of Sleep and Circadian Disorders at Harvard, commented on the bright light emitted.

“This light has serious consequences on our sleep and on our alertness, not only while we’re using these electronic devices but the following morning as well, even after eight hours of sleep.”

The study used 12 young adults, and had them interchange e-readers and traditional books. For five consecutive evenings, the participants read for around four hours before bedtime in a dimly lit hospital room. Half used e-books, while the other half used traditional books.

At the five day mark, the participants changed what they were reading, and did another five evenings of reading. The adults that used the e-reader or tablet took about 10 minutes longer to fall asleep.

Rating themselves, participants using tablets or e-books rated themselves as less sleepy before bed. Time spent in REM sleep was also shorter. In blood tests, researchers found that e-readers or tablets delayed the natural nightly increase of melatonin by more than 30 minutes.

The effects were even more pronounced in the morning. It turns out, the Netflix hangover is real. Participants using the tablets reported that they were sleepier and it took longer for them to fully wake up. Now I have science on my side for that excuse.

Blue Light and Sleep

Devices such as the iPad emit heavy doses of blue-wavelength light. In previous studies, blue light has been shown to inhibit melatonin production and decrease alertness.

Other devices that emit blue-wavelength light include laptops, cell phones and monitors. According to a 2014 National Sleep Foundation study, 89 percent of adults and 75 percent of kids have at least one electronic device in their bedroom. I fall into the category of more than 3.

Kristen Knutson, a research fellow with the foundation, expressed concern about the prevalence of devices in the bedroom. “There could be serious effects if you use these devices night after night. People need to be more mindful. Think about when you’re using them. You could think of electronics as similar to junk food. Eating junk food is fine from time to time, but you have to do it in moderation.”

Yeah, but junk food is so much better with a Netflix binge. Want to get better sleep? Read a printed book or get an e-reader that doesn’t emit light.

Unlit e-readers give off a reflective light similar to a printed book. As for those ‘reading’ but actually watching Netflix? At least you know why you’re sluggish in the morning. Knowing is half the battle.

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