Boston

Using light-emitting tablet devices in the evenings can delay bedtimes, interfere with a sleep-regulating hormone, and impair alertness in the morning, a study has found. The study, published in the journal Physiological Reports, compared nine healthy adults for five consecutive evenings of unrestricted use of light-emitting tablet computers versus evenings reading from printed materials. “These findings provide more evidence that light-emitting electronic devices have biological effects,” said Jeanne Duffy, from Harvard Medical School in the US. “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,” said Duffy. On evenings when using light-emitting tablets, participants’ self-selected bedtimes were on average half an hour later, and they showed suppressed melatonin levels, delayed timing of melatonin secretion onset, and later sleep onset. Melatonin is a hormone that regulates sleep and wakefulness.