ABSTRACT: In the past 50 y, there has been a decline in average sleep duration
and quality, with adverse consequences on general health. A
representative survey of 1,508 American adults recently revealed
that 90% of Americans used some type of electronics at least
a few nights per week within 1 h before bedtime. Mounting
evidence from countries around the world shows the negative
impact of such technology use on sleep. This negative impact on
sleep may be due to the short-wavelength–enriched light emitted
by these electronic devices, given that artificial-light exposure has
been shown experimentally to produce alerting effects, suppress
melatonin, and phase-shift the biological clock. A few reports have
shown that these devices suppress melatonin levels, but little is
known about the effects on circadian phase or the following sleep
episode, exposing a substantial gap in our knowledge of how this
increasingly popular technology affects sleep. Here we compare
the biological effects of reading an electronic book on a light-emitting
device (LE-eBook) with reading a printed book in the hours
before bedtime. Participants reading an LE-eBook took longer to
fall asleep and had reduced evening sleepiness, reduced melatonin
secretion, later timing of their circadian clock, and reduced nextmorning
alertness than when reading a printed book. These results
demonstrate that evening exposure to an LE-eBook phase-delays
the circadian clock, acutely suppresses melatonin, and has important
implications for understanding the impact of such technologies on
sleep, performance, health, and safety.
FULL ARTICLE AVAILABLE AT: http://www.pnas.org/content/early/2014/12/18/1418490112
