YOUR bedtime e-reader habit may be robbing you of sleep rather than helping you drift off, a U.S. study has found.

    Light emitted by devices such as the Kindle Fire, Nook Color and iPad affected the body’s release of the sleep hormone melatonin, the study by researchers at Pennsylvania State University found.

    “Electronic devices emit light that is short-wavelength-enriched light, which has a higher concentration of blue light,” said Anne-Marie Chang, assistant professor of biobehavioral health at Penn State.

    “This is different from natural light in composition, having a greater impact on sleep and circadian rhythms,” Chang said.

    The study observed the sleep patterns of 12 adults over two weeks to compare their sleep when they read from an iPad to reading a printed book at night.

    Researchers found participants took almost 10 minutes longer to fall asleep after reading from light-emitting iPads than they did after reading a conventional book.

    Participants also had a lower amount of REM, or rapid eye movement, sleep after reading from iPads. “Our most surprising finding was that individuals using the e-reader would be more tired and take longer to become alert the next morning,” said Chang. “This has real consequences for daytime functioning.”

    Participants stayed at a Boston hospital for the duration of the study, where their brainwaves, breathing and heart rate were monitored.

    Each person read from an iPad for five nights in a row as well as reading for five consecutive nights from a conventional book, for four hours from 6 p.m. to 10 p.m.

    Chang said the effect of such reading devices used at night warranted further study as there may be longer-term health consequences. (SD-Agencies)