He had Alzheimer's, which is a deadly disease. Alzheimer's worsens over time. Alzheimer's is a progressive disease, where dementia symptoms gradually worsen over a number of years. In its early stages, memory loss is mild, but with late-stage Alzheimer's, individuals lose the ability to carry on a conversation and respond to their environment. Alzheimer's is the third leading cause of death in the United States. Those with Alzheimer's live an average of eight years after their symptoms become noticeable to others."