A dementia is a medical condition that disrupts the way the brain works.
AD affects the parts of the brain that control thought, memory, and language.
Every day, scientists learn more about AD, but right now the cause of the disease still is unknown, and there is no cure. The disease usually begins after age 65, and risk of AD goes up with age. While younger people also may have AD, it is much less common. About 3 percent of men and women ages 65 to 74 have AD, and nearly half of those age 85 and older may have the disease. It is important to note, however, that AD is not a normal part of aging.