Study: Exercise Lowers Dementia Risk According to a new study published in the Annals of Internal medicine, people 65 and older who did moderate exercise had a significantly reduced risk of developing dementia. According to researchers, just 15 minutes of exercise three times a week lowered the risk of developing dementia by 30 to 40 percent.
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JOE PALCA, host:

For the rest of this hour, exercise and dementia. According to a new study published last week in the Annals of Internal Medicine, people 65 and older who did moderate exercise had a significantly reduced risk of developing dementia. According to researchers, just 15 minutes of exercise three times a week lowered the risk of developing dementia by 30% to 40%.

Joining me now to talk more about it is the study author, Eric Larson. He's director and senior investigator at the Center for Health Studies, part of the Group Health Cooperative in Seattle, Washington. Thanks for talking with us today.

Dr. ERIC LARSON (Director, Center for Health Studies): Thank you for having me.

PALCA: So, I'm wondering, I mean, why did you think to even ask the question, Does exercise have an influence on dementia?

Dr. LARSON: Well, we're in the midst of a long-term study which is designed to try to find ways to reduce the risk of dementia, either by preventing it or delaying it. One of the candidates for this is regular physical activity. We've been studying a group of persons, over 2,500 people, since 1994, and one of the events that happened fairly frequently is people exercised, and so it was one of the earliest things we looked at because there is some suggestive evidence that it may help, from other studies.

PALCA: I should say, if you want to join this conversation or if you have questions about the relationship between exercise and dementia, our number is 800-989-8255. That's 800-989-TALK. So, is there a biological reason to think that exercise might have a role in preventing dementia?

Dr. LARSON: There are several theories, and none of them have been proved. But the theory that I think is most promising relates to a part of the brain called the hippocampus. That's the part of the brain where memory function is mostly located, and it's also the part of the brain that shows the earliest changes when people start to develop Alzheimer's disease. Plus, it's uniquely susceptible to the effects of low blood flow or low oxygen levels. So, one theory, which I think is a good one, is that if you can improve the blood flow to the brain in general, and especially to this part of the brain, or improve its ability to withstand stress, you might reduce the risk of this degeneration occurring any earlier than necessary; the idea being that people who exercise or who are more fit actually have slower rates of degeneration, perhaps, in the hippocampus.

PALCA: And what kind of exercise are we talking about? Is this a, you know, 50-mile bike ride?

Dr. LARSON: No. That's the really interesting thing about our study. We asked people when the enrolled how many times per week do you participate, on average, at least 15 minutes in the, you know, a list of exercises. And the exercises we asked them about were walking, hiking, aerobics, calisthenics, swimming, water aerobics, weight training, and stretching. And we found that, and we don't measure the intensity of this, but these people are 65, 75, 85, and 90 when they come into this study, so it looked to us that it was rather modest levels of exercise, in most cases.

PALCA: Hm. And is there any indication about exercise, I mean, you started with people who were 65 and older; is there a lifelong benefit from exercise? Or do we know that?

Dr. LARSON: Well, we know it from other studies that there is a lifelong benefit from exercise, for many other chronic conditions like heart disease and osteoporosis and what have you. But our study really focused on cognitive decline and risk of dementia and Alzheimer's disease. There've been some studies which showed that exercise in mid-life seems to reduce the risk of Alzheimer's disease, and those studies actually were, showed that the exercise level needed to be a bit higher.

In our research though, the thing that's really interesting is that low levels seem to reduce the risk or was associated with a reduced risk. And even more interesting, the people that got the most benefit were the people that appeared to have already started to decline. So their risk reduction was greater if they exercised compared to persons who did not. And that led to this sort of, we used to say "use it or lose it" with regard to exercise and a sort of general principle of aging. I now believe that you can say to people, "Use it even after you start to lose it." PALCA: Hm. Hm. Interesting. That's a good way to think of it. Let's take a call now, and why don't we go to Lynn (ph) in Iowa City. Oh, I'm sorry, that call is blocked at the moment. We'll wait just a moment and see if we can get through to her, to Lynn.

What I was wondering about, about your study, is you were able to look at a group of people over time. Is this kind of research easier to do when you're talking about an HMO or something like that? And does that sort of determine what kind of patient population you're going to study?

Dr. LARSON: Good question. It is much easier to do when you have the enumerated population and the people in the population all get their care from the same place. And in our cooperative, in Seattle, we have a group of people who actually believe in research and are quite willing to participate and are very devoted to this study. Now the question that you need to ask as a scientist is, is this group generalize-able to rest of the population? And in the case of Seattle it turns out that it is quite generalize-able. But we do know that people who volunteer for studies are a little different than people who don't.

PALCA: Yeah. And how, I mean you started this 1994, have you, have people been dropping out or did they really stick with it?

Dr. LARSON: We do have a few people who drop out because they move, and we actually follow them if they're willing to stay in the study. And we have a few people who drop out just because they're tired of being in the study or their lives get to complicated to participate. But by and large, our follow up is what other scientists, I think, envy quite a lot.

PALCA: We're talking with Eric Larson. He's the Director and Senior Investigator in the Center for Health Studies, Group Health Cooperative in Seattle, Washington.

I'm Joe Palca, and this is TALK OF THE NATION from NPR News.

And now let's see if we can get Lynn on the line. Lynn, welcome to Science Friday.

LYNN (Caller): Good afternoon.

PALCA: What's your question?

LYNN: I'd like to know if the researchers' findings can be generalized to higher risk populations. For example, individuals who have diabetes or other neurodegenerative diseases like MS or Parkinson's disease?

PALCA: Okay, Lynn, thanks for that question.

LYNN: Also, I'd like to know if other people can participate in the study if they don't live in that area, and other places where that research is being done.

PALCA: Okay. Dr. Larson?

Dr. LARSON: Yeah, I think that it's fair to generalize these results to people have chronic diseases like diabetes, because we had them in our population, and it looked like the effect was uniform. And again, as I said a little earlier, the people who start to decline are often people who have these other chronic diseases. And I personally believe that those people benefit more from regular exercise than almost anybody. Because we have a tendency when we get a condition that slows us down to want to lie down, and to, as people say, go to bed or go to ground. And that's the time to resist the temptation, to just stop doing everything.

We don't have any information, really, about conditions like MS from our study, but I think there's pretty good evidence that almost any neurodegenerative disease would benefit; a person with that disease would benefit if they stayed physically active. We're working on some other projects that make this connection between brain and body, and I think the evidence is pretty strong.

PALCA: Lynn, oh, sorry, Lynn was also wondering if she could get in the study...

Dr. LARSON: Yeah.

PALCA: ...I think she's calling from Iowa.

Dr. LARSON: This is a study which we randomly sample a population, so ironically we don't use volunteers; because it makes the type of research that we're doing, which is epidemiology, more generalize-able if we don't do volunteers. But in almost every community across the country there are now Alzheimer's disease research centers, some called ADC's, and if you went to the National Institute on Aging website I'm sure you could find if there's a center in your area that has an interest in recruiting volunteers for research.

PALCA: Okay, Lynn, thanks very much for that call. Let's take one more quick call from Kim, in Raleigh. I guess that's North Carolina. Kim(ph), welcome to the program.

KIM (Caller): Hi. Good afternoon. I was calling to inquire about what I suppose would be a confounding variable. We know that, or we suspect strongly that folks who pursue intellectual functions and intellectual exercise tend to decline less. Were you able to wipe that variable out of your study?

PALCA: Hm. Interesting. Dr. Larson?

Dr. LARSON: We controlled for educational level. We didn't control for level of educational activity. And that's a good question. In fact the editorialist in the journal we published our paper in said one of the interesting issues is, is this a marker for a more engaged lifestyle? And that's a really hard thing to measure, but it's a perfectly legitimate question. Because there's research from Sweden and really now around the world showing that, in general, non-physical, leisure time activities reduced the rate of cognitive decline. And interestingly, it seems to be more beneficial to persons who are less educated. So a blue-collar worker who engages in intellectual activities reduces their risk of cognitive decline more than a professor; which, I think, is a fascinating observation.

PALCA: Fascinating, but probably one that is going to be answered by future research.

Anyway, we've run out of time, so I'd like to thank my guest, Eric Larson. He's Director and Senior Investigator at the Center for Health Studies, part of the Group Health Cooperative in Seattle, Washington. Thanks for talking with us today.

Dr. LARSON: It's my pleasure.

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