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Who wants SLEEP DEPRIVATION for Christmas?

Boffins say iPads-as-books mess with your circadian rhythms

If you've popped an iPad under the tree, thanks for your generosity: you've given the gift of poor sleep, disrupted circadian rhythms and an increased chance of cancer later in life.

So says a quartet of boffins* from Harvard's Medical School and Cologne's Institute of Aerospace Medicine, after they watched twelve normal healthy adults go about their nocturnal business after reading for four hours a night.

The study was conducted because millions of us now take gadgets to bed, they emit lots of light and “light is the most potent environmental signal that impacts the human circadian clock and may therefore play a role in perpetuating sleep deficiency.”

The boffins ad that “exposure to light in the evening and early part of the night, even at low intensity, suppresses the release of the sleep-facilitating hormone melatonin and shifts the circadian clock to a later time.”

It's therefore assumed that using a fondleslab in bed is a bad thing, but as the boffins not little research has been done on what this means for how users feel in the morning.

The news isn't good: using a light-emitting e-reader (the boffins used iPads) “... lengthened sleep latency; delayed the phase of the endogenous circadian pacemaker that drives the timing of daily rhythms of melatonin secretion, sleep propensity, and REM sleep propensity; and impaired morning alertness.”

Brace yourself now: the study says this result is “ … of particular concern, given recent evidence linking chronic suppression of melatonin secretion by nocturnal light exposure with the increased risk of breast, colorectal, and advanced prostate cancer associated with night-shift work.”

And in case you're wondering, the results weren't as bad for those who read a conventional book with the light on. The dozen participants were each asked to read in both modes for five nights apiece,.

The study offers a ray of light, too, in the form of some thoughts about the wavelengths of light that all fondleslabs emit. The authors say that e-readers don't really make that much light, certainly not enough to provoke the observed effects in the test population. They therefore wonder if screens' production of short-wavelength light might be the problem, and if brightness is not the best way to measure a device's potential sleep-disruption powers.

What's the bet Tim Cook has something to say about this at the next-gen iPad launch? Until then, your correspondent's classic keyboard-equipped black-on-grey Kindle is looking pretty good. ®

* We're watching you, Reddit

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