Below is a description of the effects of a rare sleep disorder, according to the MSN article:
http://health.msn.com/health-topics/articlepage.aspx?cp-documentid=100230507>1=31036 "Hallucinations and paranoia begin to take hold and eventually deteriorate into a state of dementia, according to the 'Merck Manual'. Soon, they slip into a coma-like fog and, mercifully, die. The whole process can take as little as seven months or as long as three years. There is no known cure."