Recent findings from Brigham and Women’s Hospital, in Boston, has determined that reading from a light-emitting tablet or computer before bedtime will disturb sleep and may change the circadian rhythms that govern the body’s clock.

The research, published in the Proceedings of the National Academy of Sciences, tested 12 people for two weeks. On five nights during one week, the subjects read ebooks on an iPad for four hours before bedtime. Another week, they read from printed books for the same duration.

During the five days of iPad reading, the participants fell asleep later and spent less time in rapid eye movement (REM)-stage sleep. The light-emitting tablet altered the circadian rhythm, changing the body’s natural sleeping pattern. The researchers also tested other blue-light emitting devices, including laptops, tablets, other eReaders, cell phones and LED monitors.

“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,” says neuroscientist Anne-Marie Chang, Ph.D., one of the study authors.

Dr. Charles Czeisler, Ph.D., a leading sleep researcher, remarks, “In the past 50 years, there has been a decline in average sleep duration and quality. Since more people are choosing electronic devices for reading, communication and entertainment, particularly children and adolescents who already experience significant sleep loss, epidemiological research evaluating the long-term consequences of these devices on health and safety is urgently needed.”