The more time we spend on our smartphones, the more our quality of sleep suffers. So conclude researchers in a new study in the journal PLoS ONE. "This is the first study to directly measure actual screen time in natural environments and compare it to sleep quality," the senior author tells Reuters. "We did not rely on participant self-report, but rather utilized a mobile app that ran in the background and could capture exact screen time duration." And what they found backs previous research suggesting that screen time close to bedtime is "particularly problematic" as it was "associated with longer sleep latency (or a longer time to fall asleep) and reduced sleep quality," the researcher says.
The researchers tracked 653 adults over 30 days and found that subjects used their phones for an average of 89 minutes a day. They saw no link between screen time and amount of physical exercise or body mass index or even mood, but they did when it came to quality of sleep, reports Live Science—and use right around bedtime seemed to have the greatest impact. The researchers are careful to note that their study doesn't prove causation or even explain why smartphone use might impact sleep; they hypothesize that the screens' blue light could be suppressing the sleep hormone melatonin, or that using the phone simply keeps the brain more active. Previous research has also linked smartphone use with poor sleep. (Orange-tinted eyewear can help block the blue light.)