The causes of Alzheimer's are still being studied, though more is being discovered about Alzheimer's causes every year. The causes are thought to be a combination of age-related changes in a person's brain, along with other factors like genes, the environment, and lifestyle habits.
Old age on its own does not cause Alzheimer's, but your chances of getting the disease increase as you get older. And just because someone in your family has it doesn't mean you'll get it too.
Doctors and scientists are beginning to see a link between Alzheimer's and other conditions, like heart disease, stroke, high blood pressure, and diabetes. The best thing you can do to prevent these conditions, and potentially prevent Alzheimer's is to eat a nutritious diet, stay active, get enough sleep, and keep your weight at a healthy level.