E-Readers Foil Good Night’s Sleep

The title of the article is misleading, as the participants were reading on a tablet, not an e-reader. ("During the two-week inpatient study, twelve participants read digital books on an iPad for four hours before bedtime each night for five consecutive nights.")

Having used an iPad, a Kindle, and a Kobo, I know from experience that there's a huge difference in the quality and intensity of light emitted by the devices. At its lowest setting, an iPad emits much, much more light than an e-reader at its lowest setting, and the e-readers I've used have to get above 25% or so before they begin to match the light intensity of the iPad at its lowest setting. The displays also differ in the way they're lit: tablet LCDs are backlit, and e-readers are generally front-lit, with the light being pointed at the screen and bouncing back off it.

I wouldn't be surprised if the blue/white light used on e-readers also affects sleep, but I think a study needs to be carried out using those devices before it can be concluded that they do.

The headline doesn't reflect the content: "Although iPads were used in this study, researchers also measured other devices that emit blue light, including eReaders, laptops, cell phones and LED monitors."

So, they did a user study using iPads, and only measured the other devices. They then claim the results apply to those other devices.

TFA didn't have a link to the paper (as far as I could tell), but it's here: http://www.pnas.org/content/112/4/1232.full?sid=a0e8cb09-0a5...

"The randomized, crossover protocol design consisted of two conditions: (i) reading an LE-eBook (iPad; Apple Inc., Cupertino, CA) in otherwise very dim room light for ∼4 h before bedtime for five consecutive evenings, and (ii) reading printed books in the same very dim room light for ∼4 h before bedtime for five consecutive evenings (Fig. 1)."

This seems like a strange test. When I read a physical book in bed, I need more light (e.g. from a lamp) than when I'm reading on a Kindle or an iPad (which I often read with the lights off, which also means I can turn the backlight to a low setting).

"Backlit devices" would be much more accurate, but I doubt this information is news to anyone here. I have a Kobo, but use an external LED clip light. To solve the problem, I popped the external light open and replaced the "white" LED (which are actually blue) with and RGB LED and only connected the red and green LED. It is plenty bright for reading, but I am surprised that I've never found an actual product that does this.

E-Readers is wrong. The study used as a "light-emitting" book an iPad (p. 1235). So it is tablets and smartphones. It is not even clear to me if a Kindle Paperwhite would fall into the category.

Note: the people reading paper books were allowed to adjust their position and the book's position while reading.

The people reading the "LE-eBook" (i.e.: iPad) were forced to do their reading with the iPad locked into position and the brightness turned to maximum, for four hours.

I find it hard to accept the study's findings that it was "use of these devices [that] prolongs the time it takes to fall asleep," rather than, say, having a bright light shone in your eyes and not being allowed to shift position while reading for four hours.

The iPad's brightness can be turned down much lower than an equivalent paper book illuminated by a reading lamp. Even better, the iPad's illumination will not disturb your sleeping partner as much as a bed lamp (the latter illuminates the whole room).

I'd like to see this study repeated with paper books vs paper books, with books fixed in place on the table, and one group's books illuminated with a spotlight providing equivalent illumination to the reader's face as the maximum-brightness iPad.

Then run a parallel study with all readers using iPads, with some having the brightness fixed to maximum and others free to adjust brightness to their own comfort.