It's something that's been long suspected, and now medical science has found it to be true: reading on screens before bed is bad for you.
Researchers have discovered the use of light-emitting screens for reading before you go to sleep causes a long list of sleep-related problems.
Firstly, light from the screens will increase alertness at the very time you should be winding down, which can delay people's bedtimes. This exposure will then prolong the length of time it takes to fall asleep, which delays the circadian rhythm, which reduces the amount of melatonin (the sleepy-making hormone) that the body produces. It can also delay and reduce the amount of REM sleep, and finally it will negatively impact awareness the following morning.
This obviously exerts an awful lot of biological stress on the body. If you've ever been more than a normal level of tired, you'll know exactly how this can impact your physical and mental performance, not to mention your health and safety.
The study, published in PNAS, involved a small group of volunteers -- just 12 healthy adults -- who were tested reading normal books and light-emitting devices for four hours on five consecutive evenings using each reading method. Despite presenting some limitations due to the small sample size, and the fact participants were not tested in conditions that were exactly true to life, the resulting numbers tell a compelling story.
Melatonin levels, which all remained normal when participants were reading books, dropped dramatically when reading with electronic devices. Similarly, the onset of higher melatonin levels was delayed the following day by around 1.5 hours, showing the knock-on effect on circadian rhythm.
On average, it took people who had been reading on a tablet or similar device an extra 10 minutes to fall asleep and they experiences reduced REM compared to when they had been reading print books. Perhaps unsurprisingly, those reading on light-emitting devices were more alert an hour before bed, but in the morning, the trend was reversed, and they were sleepier than when they had been reading paper books.
While it is a universal activity, our experience of sleep can feel very unique and personal, and the science behind it has not been totally deciphered yet -- in part because of the difficulty of mimicking real-life circumstances in study conditions. It can therefore be difficult therefore to draw definitive conclusions.
That said, even prior to this study medical practitioners have generally recommended reducing screen time before bed as part of good general sleep cycle. This is only supported by the results of the study, which suggests that reading on these devices before bed could be having unintended biological consequences on us. Due to a combination of increasing availability and popularity, devices such as tablets and ebook readers (with backlights) are increasingly finding their way into peoples' hands -- and probably bedrooms. How and when we use them is something only we really can control, but this could potentially have significant impacts on other decisions we make about our health.