Fast food is causing the dementia boom—and it’s projected to get worse. Almost 3.8 million people 71 or older have dementia, according to a study published today in the New England Journal of Medicine. The rise in Alzheimer’s is partly due to the aging of baby boomers. But there is another reason. When these senior citizens were teenyboppers, the fast-food craze was just taking off: The first KFC franchise opened in 1952, the first Burger King in 1954, and the first McDonald’s and Dunkin’s Donuts in 1955. As these foods caught on, America’s meat and cheese intake soared.