While researchers could confirm the dementia diagnosis for only 36 percent, another 6 percent showed clear symptoms, says coauthor Marilyn Albert, director of the Johns Hopkins Alzheimer’s Disease Research Center and a member of AARP’s Global Council on Brain Health. An estimated 514,000 American adults developed dementia in 2020, But the study projects that number will increase to about 1 million annually by 2060 as the U.S. population ages.