While research does not have a clear answer for how long a person can live without sleep, there have been a number of nonscientific reports of people dying after prolonged sleep deprivation. Sleepio.com notes that a man with fatal familial insomnia died after six months of total sleep deprivation.
According to Dr Simon Kyle in a article on the Sleepio website, experiments on rats that were totally deprived of sleep resulted in the subjects dying or entering a near-death state within 11 to 32 days, although it was uncertain whether sleep deprivation was the main cause of the animals' death.
In the 1960s, a high school student attempted to break the record for the longest time spent without sleep. As the experiment progressed, he began to show signs impaired vision along with speech and memory issues. Reportedly, he started hallucinating toward the end of the 11-day experiment. Sleep researchers estimate that as sleep deprivation is prolonged, these symptoms can deteriorate and lead to more severe symptoms.