Why Your Tech Devices May Be Disrupting Your Sleep

— -- What you read just before you go to bed may be disrupting your sleep at night, but the content of what you are reading may not be as important as what you are reading it on, according to a new study.

The study, published Monday in the Proceedings of the National Academy of Sciences, compared two groups of adults, one group that read at night from an e-reader, or back-lit electronic book, and the second group that read traditional, hard-cover books.

The results showed that the adults who read from the e-readers were less sleepy, had less REM sleep and had impaired morning alertness the following day.

“It’s that short wavelength blue light and the theory is that it really disrupts those circadian rhythms that are so important to set our sleep and wake cycle,” said Dr. Jennifer Ashton, ABC News’ Senior Medical Contributor, who was not involved in the study.

“It also suppresses melatonin, which is the natural hormone that helps us fall sleep,” Ashton said.

The study, conducted at Brigham and Women’s Hospital in Boston and led by a Penn State University professor, concluded that the impact of light-emitting devices on users has biological effects and circadian rhythms disruptions that can, “have adverse impacts on performance, health, and safety.”

It’s not don’t use them at all,” Ashton said of the findings. “It’s don’t use them right before you’re going to sleep…unplug 30 to 60 minutes before bedtime.”

“This just isn’t for adults. It’s for our kids also,” Ashton added.

ABC News reached out to the major e-reader companies. Of those that responded, they declined to respond to the study.