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A panel convened by the National Institutes of Health says there's no sure way to prevent Alzheimer's disease or other forms of mental decline related to aging. The panel says it's possible people can reduce their risk by exercising, staying mentally active and watching their diets. But the evidence for that is still pretty limited.

Joining us to discuss the findings is NPR science correspondent Jon Hamilton. Jon, why does this group sound so negative about prevention?

JON HAMILTON: One reason is that the positive messages we've been hearing come from scientists who are actually doing research on Alzheimer's disease. They know all of the science already invested in it. This panel was deliberately put together to include top rate scientists, but not scientists who actually are doing research on Alzheimer's. They bring a different kind of perspective to it.

And one of the things was that they were not particularly interested in, say, animal studies. They were not interested in small studies. They wanted large, long-term studies of people and there really aren't that many of those that have to do with Alzheimer's prevention.

NORRIS: Let's take these preventive measures one by one. What about things like crossword puzzles or other mental exercises, do they help?

HAMILTON: You certainly hear a lot about that kind of stuff and there are some studies that have suggested that mental and social activities actually do help. For example, say, people with lots of education seem to have a lower risk of Alzheimer's. But what the panel said was that these studies were only finding an association. They didn't show that, say, education was really the thing that lowered risk, you know. Maybe it was lowered because highly educated people, they eat better or maybe they exercised more. It wasn't clear.

NORRIS: So, education, crossword puzzles, Sudoku, maybe. How about physical exercise? Have we heard that that perhaps is good for our brains?

HAMILTON: Well, there's a great circumstantial case for exercise, you know. And starting again in animals, you look and when animals exercise it seems to stimulate the production of these chemicals in the brain that help repair damage and to help the brain make new connections. Of course, that's really hard to show in people 'cause you can't just cut open their heads and take a look.

Also, exercise reduces your risk for some things that are associated with Alzheimer's. So, for instance, people who have diabetes or high blood pressure are at higher risk, and exercise reduces your risk of that. So there's this great circumstantial case. But, again, what the panel says is there really aren't good studies showing that people who exercise, that exercise is the thing that reduces the risk of Alzeheimer's and other cognitive decline.

NORRIS: What about diet? There have been lots of reports about how foods containing antioxidants might help protect the brain.

HAMILTON: The panel was really skeptical about diets and dietary supplements, and including we hear a lot about antioxidants. And their draft report, the final report, I should say, is not out yet. But the draft report said, and I, quote, "there is currently no evidence considered to be of even moderate scientific quality showing that these things work." I should say there's a little good news for people who eat fish, though. The panel said that there's pretty decent evidence for omega-3 fatty acids.

NORRIS: What's been the reaction to this report from scientists who study Alzheimer's?

HAMILTON: They're pretty cautious about criticizing the panel or the NIH, for that matter. And they say things like, well, you know, their job is to be conservative and it's good to be conservative in your assessment of these things. But leaders of groups like the Alzheimer's Association also say they're kind of worried about what the reaction will be to this.

They say they're worried that people will hear the findings and stop doing a lot of the things that might help their brains. And even if they don't help their brains, they almost certainly will help them be healthier overall.

NORRIS: So, does anything work, Jon?

HAMILTON: A couple of things might. Smoking seems to increase your risk for Alzheimers. So, quitting smoking is probably a good idea. The other thing is genetics. Its not exactly a prevention factor but if you could choose your parents, you could choose ones who dont carry certain genetic variations and you could reduce your risk.

NORRIS: Thank you, Jon.

HAMILTON: Youre welcome.

NORRIS: Thats NPRs Jon Hamilton.

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