This is what I've been saying all along. I don't need an official study to know that my mental performance, or that of others, goes down when sleep-deprived.
I hear this stuff a lot from people I've worked with; they wear it like a badge of honor and feel compelled to bring it up unasked for in conversation...even though it's killing them. People that work two jobs while raising kids and still try to fit in school or fill in the blank.
Basic mathematics will show you that there's so many hours in the day. While most of us are used to multitasking online, we're absolutely horrible at it in real-life practice, especially when a full-cognizance activity is involved like driving.
Add in cellphones behind the wheel and most of us prove we can't walk and chew gum. The people I mentioned above; they just go through the day like mindless drones and aren't really capable of an attention span beyond that of five-year old.
We're not designed to do all this; we're exceeding the limits of our biology. In our efforts to keep up with the Jones’s with a big house and car and have at least two careers and still manage to squirt out a few kids that will only end up emo or drug-addicted in fifteen years because they never got enough attention in their formative years, we're taking ourselves down. I truly believe we have an epidemic on our hands, and it's even worse because most are unaware of it.
To paraphrase Carlin, nobody notices, nobody seems to care. I feel compelled to ask if we're truly masters of all our technology and society, or if they have become the master of us?