Daylight counteracts sleep disturbances due to digital devices

Daytime exposure to bright light may counteract the sleep disturbances associated with the evening use of blue-light emitting digital devices, such as tablets, smartphones, e-readers, and laptops, according to researchers from Uppsala University, Uppsala, Sweden, who published their results in Sleep Medicine.

Although results are mixed, some studies have shown that sleep disturbances may be associated with the evening use of electronic devices that emit blue light, and may be caused by blue light-mediated suppression of melatonin, the sleep-promoting hormone. Researchers at Uppsala University assessed whether evening reading on a self-luminous tablet have any effects on sleepiness, secretion of melatonin, nocturnal sleep, and electroencephalographic power spectral density during early slow-wave sleep.

For their study, 14 subjects were required to read a novel either in book form or on a tablet after a constant bright light exposure over 6.5 hours. Researchers measured evening saliva concentrations of melatonin repeatedly, and recorded sleep via polysomnography. Subjects’ sleepiness was tested before and after nocturnal sleep. A week later, these experiments were repeated, but subjects were crossed over, and those who read from a book were required to read from a tablet and vice versa.

Researchers found no differences in any sleep parameters or in pre-sleep saliva melatonin levels between the two groups.

“Our results could suggest that light exposure during the day, e.g. by means of outdoor activities or light interventions in offices, may help combat sleep disturbances associated with evening blue light stimulation. Even if not examined in our study, it must however be kept in mind that utilizing electronic devices for the sake of checking your work e-mails or social network accounts before snoozing may lead to sleep disturbances as a result of emotional arousal,” concluded senior author Christian Benedict, associate professor, Department of Neuroscience, Uppsala University.