In the age of digital technology it is just as common to read a tablet or smartphone at bedtime as it is to read a book. However, late-night reading from light-emitting electronic devices such as smartphones or certain tablets before bedtime can prolong the time it takes to fall asleep, disrupt the circadian clock, suppress melatonin levels and reduce the amount of rapid eye movement (REM) sleep.
Moreover these physiological factors can affect how alert a person is the next day. This is based on research performed at Brigham and Women’s Hospital and Harvard Medical School, in a study led by Anne-Marie Chang.
For the research, the scientists compared the effects of reading from a light-emitting device versus reading from a printed book near a light source at bedtime by monitoring 12 healthy volunteers — six men and six women — for two weeks. The researchers compared light-emitting e-book readers versus traditional book readers through plasma melatonin levels and EEG analyses.
Through this, the researchers found evidence to suggest that “the use of portable light-emitting devices immediately before bedtime has biological effects that may perpetuate sleep deficiency,” as they state in their paper. It seems that people who already have a delayed body clock are delaying themselves much further.
Speaking with the BBC, study co-author Charles Czeisler said: “Sleep deficiency has been shown to increase the risk of cardiovascular disease, metabolic diseases like obesity and diabetes, and cancer. Thus, the melatonin suppression that we saw in this study among participants when they were reading from the light-emitting e-reader concerns us.”
The findings have been published in the journal PNAS. The study is titled “Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness.”
