People used to read a book before bedtime to calm down after a stressful day. Now, many people use a tablet, smartphone, Kindle, iPad or similar device to do their bedtime reading. A study from Harvard suggests that is probably a bad idea and could disrupt sleep.
The scientists recruited 12 young adults for the study. They read for four hours before bedtime for five days. Half were reading e-books, while the other half had print books. After five days, they shifted to the other format for an additional five days of the study.
Those reading e-books took longer to fall asleep and said they felt less sleepy. During sleep they dreamed less, and they felt groggier upon waking.
Blood tests showed that electronic reading delayed the normal nighttime peak in melatonin levels by more than an hour and a half. The scientists suspect that the blue light waves that e-readers emit trick the brain into perceiving that it is not yet nighttime.
Since nearly half of US adults keep a smartphone or tablet near the bed, this could be contributing to the national sleep debt.
