That's right. They did an experiment. Control group rats were allowed to sleep. Test group were on a wheel that would start spinning of the rat fell asleep. It would crash them into a wall that would wake them up. After 40 days, the control group was fine, but the test group were all dead.
When they looked at their internal organs, they were mush.
They use different methods to keep the rats awake. Some say the rats died after 3 weeks, some 40 days... It's pretty much a scientific fact by this point that prolonged sleep deprivation ultimately leads to death.