Over half of all Alzheimer's disease cases could potentially be prevented through lifestyle changes and treatment or prevention of chronic medical conditions, according to a study led by Deborah Barnes, PhD, a mental health researcher at the San Francisco VA Medical Center. Analyzing data from studies around the world involving hundreds of thousands of participants, Barnes concluded that worldwide, the biggest modifiable risk factors for Alzheimer's disease are, in descending order（降序排列） of magnitude, low education, smoking, physical inactivity, depression, mid-life hypertension, diabetes and mid-life obesity.

In the United States, Barnes found that the biggest modifiable risk factors are physical inactivity, depression, smoking, mid-life hypertension, mid-life obesity, low education and diabetes.

Together, these risk factors are associated with up to 51 percent of Alzheimer's cases worldwide (17.2 million cases) and up to 54 percent of Alzheimer's cases in the United States (2.9 million cases), according to Barnes.

"What's exciting is that this suggests that some very simple lifestyle changes, such as increasing physical activity and quitting smoking, could have a tremendous impact on preventing Alzheimer's and other dementias（痴呆） in the United States and worldwide," said Barnes, who is also an associate professor of psychiatry at the University of California, San Francisco.

The study results were presented at the 2011 meeting of the Alzheimer's Association International Conference on Alzheimer's Disease in Paris, France, and published online on July 19, 2011 in Lancet Neurology.

Barnes cautioned that her conclusions are based on the assumption that there is a causal association between each risk factor and Alzheimer's disease. "We are assuming that when you change the risk factor, then you change the risk," Barnes said. "What we need to do now is figure out whether that assumption is correct."

Senior investigator Kristine Yaffe, MD, chief of geriatric（老人的） psychiatry at SFVAMC, noted that the number of people with Alzheimer's disease is expected to triple over the next 40 years. "It would be extremely significant if we could find out how to prevent even some of those cases," said Yaffe, who is also a professor of psychiatry, neurology（神经学） and epidemiology at UCSF.