Phone, tablet use at bedtime may reduce sleep quality: study

Boston — Using light-emitting electronic devices at bedtime may be more detrimental to sleep quality than reading a book, according to a recent study from researchers at Brigham and Women’s Hospital and Harvard University.

The study involved nine participants between 18 and 30 years old. Over two five-day study periods, the participants read printed material or used a tablet from 6 p.m. until 8:45 p.m., at which time they took a break and a five-minute survey on their alertness. After taking the survey, they could choose to continue reading their printed material or using the tablet, or they could go to sleep.

Participants then were monitored while sleeping and took sleepiness/alertness surveys after waking at a fixed time. Blood samples provided data for both melatonin levels and circadian rhythm evaluations.

Among participants who used a tablet, researchers found that self-selected bedtimes were 30 minutes later, melatonin suppression was greater, evening sleepiness was lower, and evening alertness and morning sleepiness was higher.

“These findings provide more evidence that light-emitting electronic devices have biological effects,” Jeanne Duffy, study co-author, assistant professor of medicine at Harvard University and an associate neuroscientist at Brigham and Women’s Hospital, said in a press release. “Using light-emitting electronic devices in the late evening can postpone our decision to go to sleep, and make us more sleepy the next morning.”

The researchers cited previous studies that associated a later bedtime with a higher risk of a number of negative health and behavioral results.

The study was published online May 22 in the journal Physiological Reports.