We spend about 24 years of our lives sleeping, yet the exact function of sleep is still being debated by scientists. 

In experiments, researchers monitored three groups of participants who slept 4, 6, or 8 hours a night over an extended amount of time. After just two weeks, the group who slept 6 hours had a similar reaction time as a person whose blood alcohol concentration was 0.1 percent. Those who slept 4 hours would fall asleep during their cognitive tests.

Here's the video from AsapSCIENCE. 

People who consistently sleep less than 7 to 8 hours a night may suffer cognitive issues. People who sleep more than 8 hours don't have cognitive impairment, but like the chronically sleep deprived, they have higher risks of heart disease, obesity, and diabetes.  

There also appears to be a genetic mutation that allows a person to sleep less because of their more intense sleep sessions. 

[Via AsapSCIENCE]