Alzheimer's disease is a type of dementia. Dementia is a loss of thinking, remembering, and reasoning skills that interferes with a person's daily life and activities.

Memory problems are typically one of the first signs of Alzheimer's disease, though different people may have different initial symptoms. A decline in other aspects of thinking, such as finding the right words, vision/spatial issues, and impaired reasoning or judgment, may also signal the very early stages of Alzheimer's disease.

Alzheimer's disease progresses in several stages: preclinical, early (also called mild), middle (moderate), and late (severe). During the preclinical stage of Alzheimer's disease, people seem to be symptom-free, but toxic changes are taking place in the brain. A person in the early stage of Alzheimer's may exhibit the signs listed above.

As Alzheimer's disease progresses to the middle stage, memory loss and confusion grow worse, and people may have problems recognizing family and friends. As Alzheimer's disease becomes more severe, people lose the ability to communicate. They may sleep more, lose weight, and have trouble swallowing. Eventually, they need total care.

Scientists do not yet fully understand what causes Alzheimer's disease in most people. In early-onset Alzheimer's, which occurs between a person's 30s and mid-60s, there may be a genetic component. Late-onset Alzheimer's, which usually develops in a person's mid-60s, arises from a complex series of age-related brain changes that occur over decades. The causes probably include a mix of these changes, along with genetic, environmental, and lifestyle factors. These factors affect each person differently.

Currently, there is no cure for Alzheimer's disease.

The U.S. Food and Drug Administration (FDA) has approved several drugs to treat people with Alzheimer's disease, and certain medicines and interventions may help control behavioral symptoms.

Scientists are developing and testing potential new treatments for Alzheimer's. Participation in clinical trials is crucial for helping scientists learn about the brain in healthy aging and what happens in Alzheimer's and other dementias. The results of these trials are used to improve diagnosis, treatment, and prevention methods.

Currently, there is no definitive evidence about what can prevent Alzheimer's disease or age-related cognitive decline. What we do know is that a healthy lifestyle — one that includes a healthy diet, physical activity, appropriate weight, and control of high blood pressure — can lower the risk of certain chronic diseases and boost overall health and well-being. Scientists are very interested in the possibility that a healthy lifestyle might delay, slow down, or even prevent Alzheimer's. They are also studying the role of social activity and intellectual stimulation in Alzheimer's disease risk.