http://goo.gl/qRq53C
Not getting enough sleep is detrimental to both your health and productivity. Yawn. We've heard it all before. But results from one study impress just how bad a cumulative lack of sleep can be on performance. Subjects in a lab-based sleep study who were allowed to get only six hours of sleep a night for two weeks straight functioned as poorly as those who were forced to stay awake for two days straight. The kicker is the people who slept six hours per night thought they were doing just fine.
As you can imagine, the subjects who were allowed to sleep eight hours per night had the highest performance on average. Subjects who got only four hours a night did worse each day. The group who got six hours of sleep seemed to be holding their own, until around day 10 of the study.
In the last few days of the experiment, the subjects who were restricted to a maximum of six hours of sleep per night showed cognitive performance that was as bad as the people who weren't allowed to sleep at all. Getting only six hours of shut-eye was as bad as not sleeping for two days straight. The group who got only four hours of sleep each night performed just as poorly, but they hit their low sooner.