about 1 in 3 of people age 85 or older have Alzheimer's dementia
Age is the greatest of these three risk factors. As noted in the Prevalence section, the percentage of people with Alzheimer's dementia increases dramatically with age: 3% of people age 65-74, 17% of people age 75-84 and 32% of people age 85 or older have Alzheimer's dementia