Smartphones keep you awake

Iranian MPs sleeping in Majlis ParliamentExposure to smartphone screens will stuff up your sleep, according to a new study.

Writing in the science journal PLOS ONE, which sounds more like a mathematics magazine for dyslexics, Matthew Christensen from the University of California, San Francisco and his chums wondered what the physical effects of increased smartphone use was having on the great unwashed.

Christensen and colleagues tested the hypothesis that increased screen-time may be associated with poor sleep by analysing data from 653 adult individuals across the United States participating in the Health eHeart Study.

Participants installed a smartphone application which recorded their screen-time, defined as the number of minutes in each hour that the screen was turned on, over a 30-day period. They also recorded their sleeping hours and sleep quality.

Each participant used their phones 38.4 hours over this period, with smartphones being activated on average for 3.7 minutes in each hour. Longer average screen-time was associated with poor sleep quality and less sleep overall, particularly when smartphones were used near participants’ bedtime.

The first to measure smartphone exposure prospectively, but caution that the study also had some limits which means that the authors cannot show causation or exclude the “effect-cause” that poor sleep could lead to more screen time. What they did find was a theory that bedtime smartphone use may negatively impact sleep.