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The rate at which older Americans are getting Alzheimer's disease and other forms of dementia has dropped. That's according to a study published today in the American Medical Association's journal Internal Medicine. The researchers say the decline has something to do with an increase in education levels. NPR's Ina Jaffe reports.
INA JAFFE, BYLINE: The study took two snapshots - one in 2000 and another in 2012. Each time, it looked at more than 10,000 Americans who were at least 65 years old. In the first snapshot, 11.6 percent of them had some form of dementia. In the second snapshot, it was less than 9 percent. If that difference sounds small, it's not, says John Haaga, who directs the Division of Behavioral and Social Research at the National Institute on Aging which funded the study.
JOHN HAAGA: That's well over a million people who don't have dementia but would have had it if the rates had stayed the same as the 2000 rates.
JAFFE: While the prevalence of dementia cases dropped, the average amount of education in the study population increased from not quite finishing high school to completing high school and just a little bit of college. Dr. Kenneth Langa, a professor of medicine at the University of Michigan and the lead author of the study, says that researchers don't know why education should be a protector against dementia, but they have some theories.
KENNETH LANGA: One is that education might actually change the brain itself. We think that it actually creates more complicated connections between the nerve cells so that you're able to continue thinking normally later into life.
JAFFE: Education can not only change the brain. It can change your whole life, says John Haaga.
HAAGA: It affects what kind of work you do of course. It also affects who your friends are, who you're married to, whether you're married. All aspects of life are affected by educational attainment.
JAFFE: But the study doesn't say that education alone is the X factor in preventing dementia. There are medical factors, too. Cardiovascular conditions believed to increase the risk of dementia - things like high blood pressure or high cholesterol - are going up, but these days, they're being treated more aggressively, says Haaga.
HAAGA: So it could well be that we're getting better at managing the bad effects of these risk factors. But they are still risk factors.
JAFFE: This study fits a recent trend. In the past decade or so, other researchers have found similar declines in dementia risk in wealthier nations, but the study populations haven't been very diverse. Kenneth Langa says that his research is part of the ongoing health and retirement study that follows about 20,000 older Americans of all backgrounds nationwide.
LANGA: So I think the fact that our study also shows a decline, you know, provides additional evidence that this phenomenon seems to be going on across the United States and not in one particular geographic region.
JAFFE: But while the risk of dementia is declining, the number of cases is still expected to rise. That's because the population of older adults in this country is increasing. The number of people 65 and older is expected to nearly double by 2050. Ina Jaffe, NPR News.
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