PARIS — If the known risk factors in Alzheimer's disease were actually modified to a relatively modest degree, nearly half a million Americans with the condition might have avoided it, according to a study presented here.
A 10-to-25 percent reduction in seven risk factors for dementia, including diabetes, midlife hypertension, midlife obesity, smoking, depression, lack of mental stimulation, and physical inactivity, could have theoretically prevented up to 492,000 cases of Alzheimer's disease over the next 40 years, Deborah Barnes and Dr. Kristine Yaffe of the University of California San Francisco reported.
The results, presented at the Alzheimer's Association International Conference on Alzheimer's Disease, were also published online in Lancet Neurology.
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Using the same calculations on a worldwide basis, Barnes and Kristine Yaffe found that 50.7 percent of the risk for Alzheimer's disease globally is related to these seven factors, leading to more than 17 million new cases if current prevalences continue.
On the basis of these figures, reducing the prevalence of all seven risk factors by 10 percent would cut the global and U.S. case counts by 1.1 million and 184,000, respectively. Prevalence reductions of 25 percent would correspondingly prevent some 3 million and 492,000 globally and in the U.S., respectively.
Barnes and Yaffe emphasized that all seven of the risk factors are modifiable. In the rest of the world, the findings suggest that making inroads into the prevalence of low education and smoking would have the greatest effect on Alzheimer's disease incidence.
In the U.S., however, physical inactivity is the most significant factor, in part because it helps drive three of the other risk factors -- diabetes, obesity, and hypertension. Barnes and Yaffe also argued that increasing physical activity often boosts mental activity as well.
"Public health campaigns targeted at increasing the amount of physical activity on a societal level could have a profound effect on future AD prevalence," they wrote in their Lancet Neurology report.