Casey Kasem Casey Kasem entertained different generations of children as the voice of Shaggy in the animated television series, Scooby Doo. He was also known as the voice of the American Top 40 countdown. In 2007, Kasem was diagnosed with Lewy Body Dementia and died in 2014 at the age of 82. Potential Alzheimer’s treatment in Phase 3 clinical trials gets boost from the FDA. Find out more.