This is a question I often ask myself, especially late at night when I just want to watch one more hour of American Pickers.
Even when I'm sleeping less, I've noticed that I'm "fine," but it seems that is just me getting used to the lack of sleep!
Studies were conducted that show that when people can only sleep for 4 or 6 hours a night for a prolonged period of time, cognitive function decreased almost linearly with time and showed no signs of leveling off
This can be called "sleep debt." You can recover with a few nights of good sleep, but it's unknown if there are long-term side effects to this. Scientists say 7-8 hours of sleep per night is ideal for most humans.
If you consistently sleep less than 7 hours, you are at a higher risk for heart disease, obesity, diabetes, but if you sleep consistently more than 7 hours, you're also at a risk! So, don't sleep too much either!
So, what about you: how much sleep do you REALLY need?