"When subjects read on the iPad as compared to the paper books ... people reported feeling less sleepy at night and less alert the following morning ... empirically, they also took longer to fall asleep on the iPad nights and spent less time in the REM phase of sleep. And the blood tests showed that on average, the brain's melatonin secretion on those nights was delayed by an hour and a half."
Someone(s) out there likes blue light :) They should read http://www.theatlantic.com/health/archive/2014/12/no-ipads-i...
"When subjects read on the iPad as compared to the paper books ... people reported feeling less sleepy at night and less alert the following morning ... empirically, they also took longer to fall asleep on the iPad nights and spent less time in the REM phase of sleep. And the blood tests showed that on average, the brain's melatonin secretion on those nights was delayed by an hour and a half."