I believe this was a flawed conclusion. Some people stay up late and wake up with the light, lowering the amount of time that they sleep, which in turn lowers their IQ.
My wife stays up to the same time, sleeps late, and has not shown the same decrease in IQ.
But, here are a few mentions of study results on lack of sleep causing lower IQ and light keeping people awake:
http://www.cbc.ca/health/story/1999/03/20/sleep990320.html
http://www.livescience.com/health/teens-sleep-morning-light-...
And here are some alarm clocks that wake people up with light:
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dap...