Authors examined five recent studies that suggest a decrease in the prevalence of dementia, crediting the positive trend to improvements in education levels, health care and lifestyle.

"We're very encouraged to see a growing number of studies from around the world that suggest that the risk of dementia may be falling due to rising levels of education and better prevention and treatment of key cardiovascular risk factors such as high blood pressure and cholesterol," says co-author Kenneth Langa, M.D., Ph.D., a professor of Internal Medicine at the U-M Medical School and research investigator at the Center for Clinical Management Research (CCMR), VA Ann Arbor Healthcare System.

"Our findings suggest that, even if we don't find a cure for Alzheimer's disease and dementia, there are social and lifestyle factors we can address to decrease our risk."

Authors also include Eric B. Larson, M.D., M.P.H., executive director of Group Health Research Institute and Group Health's vice president for research; and Kristine Yaffe, M.D., a professor of psychiatry, neurology, and epidemiology and biostatistics at the University of California, San Francisco. Larson is also an adjunct professor at the University of Washington Schools of Medicine and Public Health.

Authors point to two key factors that may explain the decreased risk of dementia over the last few decades: People are completing more years of school, which helps the brain fight off dementia; and there's more awareness and focus on preventing heart disease, another big risk factor for Alzheimer's.

"The growing number of older adults in the U.S. and around the world means we will undoubtedly see a significant growth in the number of people with dementia, however the good news is they appear to be living longer without experiencing it," says Langa, who is also a member of the U-M Institute for Social Research, Institute of Gerontology and Institute for Healthcare Policy and Innovation.

"We are seeing a positive trend that suggests that improving our physical and mental health go hand in hand with fighting off this devastating condition."

In 2008, Langa and Larson reported one of the first studies suggesting a decline in U.S. dementia rates, using information from the U.S. Health and Retirement Study. They found that decline tracked with education and improvements in health care and lifestyle. Since then, several studies in Europe have confirmed this trend -- and the reasons behind it.

Other research has also shown that other factors decreasing risk include early and ongoing education, physical activity, retiring later, educated parents (especially an educated mother), maintaining social activities and getting treatment for depression.