(RxWiki News) Love reading before bed? You may want to stick with an old-fashioned book and leave the e-reader on the charger.
A new study found that people who read on e-book readers for about four hours before going to bed took longer to fall asleep and had less restful sleep than those who read printed books.
"We found the body's natural circadian rhythms were interrupted by the short-wavelength enriched light, otherwise known as blue light, from these electronic devices," said lead study author Anne-Marie Chang, PhD, of Brigham and Women's Hospital in Boston, in a press release.
According to Dr. Chang and team, sleep duration and quality has been declining for the past 50 years. Past studies have linked use of electronic devices at night to poorer sleep habits.
This study focused specifically on electronic reading devices that emit light, such as iPads.
These researchers recruited 12 young adults in their 20s for this 14-day study.
Each patient read an e-reader for about four hours before they went to bed for five evenings in a row. Then they read a printed book for the same amount of time for another five consecutive nights.
Dr. Chang and colleagues took blood samples and monitored the patients' sleep over the course of the study. The patients also reported how sleepy they felt each evening and morning.
These researchers found that, when the patients used an e-reader, their melatonin levels were about 55 percent lower than when they read a printed book. Melatonin is a hormone that regulates sleep.
Also, after reading an e-book, patients took about 10 minutes longer to fall asleep than they did after reading a printed book. They also spent less time in rapid eye movement (REM) sleep, which is important for restfulness.
The patients also felt less sleepy in the evenings but sleepier in the mornings when they read e-readers rather than printed books.
Dr. Chang and team concluded that using e-readers in the hours before bed could contribute to low sleep quality and sleep loss.
This study was published Dec. 22 in PNAS .
The National Institutes of Health and the National Center for Research Resources funded this research. Some of the study authors disclosed financial ties to Merck, Novartis and other pharmaceutical companies.
