Curling up with an iPad might not be as restful as one might hope as the electroluminescent glow inhibits the production of melatonin. And you might drop it too.

So says the Director of the UCLA Sleep Disorders Center, Frisca Yan-Go, who reckons that having that much light right in front of the eyes prevents the brain producing the melatonin one needs to get a good night’s sleep, as reported by the LA Times.

Which is bad news for electronic books on the iPad, though it's not all good for e-ink devices like the Kindle or Cool-Er. Apparently the limited contrast of e-ink screens can cause eye-strain, but at least those with strained eyes are well rested.

E-ink screens don’t offer the same contrast as a high-quality printed book, but fare better when compared to a cheap paperback, so it’s a matter of personal taste – if e-ink hasn’t the contrast for you then go for an iPad, but any problems sleeping and you’re better off with e-ink.

Not that sleeping is the only risk one takes reading an iPad in bed: Frisca Yan-Go reckons that books are lighter and less worrisome when dropped, assuming one manages to get to sleep what with the worry and the lack of melatonin.

But we’re not convinced – the e-book edition of Legacy of Ashes is an awful lot easier to read in bed than the hardback, and e-books don’t squash your thumb all night if you do doze off.

It’s too early to say if melatonin inhibition hits a significant proportion of iPad users, or impacts how people use the device, but if nothing else the issue will be keeping a few Apple executives awake for a while. ®