January 2015 — A study by Brigham and Women’s Hospital and Harvard Medical School has found that using light-emitting e-readers before bed can harm sleep quality.
For two weeks, researchers monitored 12 adult volunteers who were instructed to read from either e-readers or printed books before bed, under controlled conditions in a sleep lab. Those who used e-readers took about 10 minutes longer to fall asleep at night and were less alert in the mornings than those who read from printed books.
The e-reader users also had significantly lower amounts of REM sleep, which is the important, regenerative sleep cycle characterized by rapid eye movements. The researchers believe the poor sleep quality is due to the higher concentration of blue light emitted from e-readers and digital tablets. This type of light suppresses levels of the sleep-promoting hormone melatonin and can shift circadian rhythms, curbing the urge to fall asleep until later.
If you have problems falling asleep, or if you feel groggy in the morning, try cutting down on your digital device usage at night.
This study appeared in December in Proceedings of the National Academy of Science. — N.B.