Watched a 60 Minutes report on sleep deprivation.
Test subjects which slept around 4-5 hours per day for a week had a very high risk of type-2 diabetes. Sleep deprivation is also being linked to obesity, as the hormone which tells you that you are hungry gets produced more (even when you just ate). Sleep refreshes your memory, as subjects could remember more the next day when having slept the night as opposed to studying all night. Subjects which were sleep deprived reacted stronger to negative comments and were more easily angered. Subjects which were impaired still thought they could drive a car even when they obviously were in no shape to do so. And mice which were starved of sleep started dying 5 days into the test (take that however you wish).
Just a few things i thought i would share