Power down to rest up: light-emitting tablets disrupt sleep and melatonin levels

One of my favourite parts of the day is when I get to change into my pajamas and bury myself in blankets and a good book. After a long and busy day, I look forward to my quiet time when I can decompress and read about Cheryl Strayed’s long hike or why Gwyneth Paltrow is wrong about everything (review coming soon!). My husband, on the other hand, prefers to spend this time driving racecars on his phone or reading about new gadgets on our iPad. According to new findings from Harvard Medical School and Brigham and Women’s Hospital in Boston, these differences in our bedtime routines could be the reason why I generally sleep much better than my husband.

In a study published in the Proceedings of the National Academy of Sciences, Anne-Marie Chang and her colleagues found that reading on light-emitting eReaders before bed negatively affected sleep by altering levels of melatonin. The researchers recruited 12 participants and randomly assigned them to one of two groups: one group read printed books for four hours before bed every day for five consecutive days while the other group used eReaders. After five days, the participants switched to reading on the other device. This study design allowed researchers to compare sleep-related metrics from the same individual when they were reading a printed book to when they were reading an eReader. The eReaders used in this study were iPads set to maximum brightness.

There is nobody else I'd rather lie in bed and look at my tablet next to. (Source)
There is nobody else I’d rather lie in bed and look at my tablet next to. (Source)

Melatonin is a hormone that helps to controls your sleep cycles. If your eyes get progressively droopier as the clock ticks towards your 11:00 pm bedtime, that’s because your melatonin levels are rising and telling your body it needs to sleep. When participants read from an iPad, they had lower levels of melatonin and rated themselves as less sleepy an hour before bedtime. The timing of melatonin release was also affected. Melatonin release was delayed by more than one and a half hours when participants used an iPad compared to when they read a printed book, essentially shifting the sleep cycle to a later time. Continue reading