Professor Tony Elliott presents information on dementia and Alzheimer's disease, including: 1) Dementia is characterized by memory loss and functional decline, while Alzheimer's is the most common cause of dementia. 2) The prevalence of dementia doubles every 5 years after age 65, affecting 5% of those over 65 and up to 32% of those over 90. 3) The brain changes in Alzheimer's include plaques, tangles, and loss of connections between neurons. 4) Risk factors include age, family history, and genetic factors like ApoE4, while preventative factors include diet, exercise, and mental activity.