Scientists say lifestyle changes, such as healthier eating and more education, could prevent people from developing Alzheimer's disease and other forms of dementia.
Several studies presented this week at the Alzheimer's Association International Conference in Copenhagen support this view.
One trial in Finland found two years of exercising, diet, cognitive training and other changes improved people's memory function.
Research also shows a decline in the rate of dementia in the United States, Germany and other developed countries. A U.S. study concluded an American over age 60 today has a 44 percent lower chance of developing dementia than a person the same age 30 years ago.
Researchers say reasons for this could be declines in smoking, heart disease and strokes - all factors linked to dementia - as well as improvements in blood pressure and cholesterol levels.
But scientists caution that the growth of diabetes and obesity could offset these gains. And in poor countries, behind in education and health, dementia seems to be rising.
In the United States, more than five million people have Alzheimer's. The non-profit Alzheimer's Disease International says dementia, of which Alzheimer's is the most common form, affects more than 44 million people worldwide. The group says that number is expected to triple to more than 135 million by 2050.
The age-related brain condition, which gradually robs patients of their ability to think, remember and care for themselves, is rising partly because people are living longer.
In addition to the focus on lifestyle as prevention, some are looking to medications to fight Alzheimer's.
Swiss drugmaker Novartis plans to test two experimental Alzheimer's drugs in people who are genetically predisposed to the disease, but do not yet have symptoms. The company is collaborating with the Banner Alzheimer's Institute in the U.S. state of Arizona.
