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At an international meeting, Alzheimer's researchers are assessing what comes next

ARI SHAPIRO, HOST:

Research on Alzheimer's disease is at a crossroads. Experimental drugs have been a disappointment so far, so researchers are trying to figure out what comes next. NPR's Jon Hamilton has been attending the Alzheimer's Association International Conference in San Diego this week, and he joins us now. Hey, Jon.

JON HAMILTON, BYLINE: Hey.

SHAPIRO: Why are these drugs that researchers were once optimistic about failing?

HAMILTON: These drugs are going after something called amyloid. It's the thing that forms the sticky plaques that tend to build up in the brains of people who have Alzheimer's. And some of the drugs have proved really good at removing these plaques. But they don't seem to prevent memory loss. So even the one anti-amyloid drug that's approved by the FDA - that's a drug called Aduhelm - it still hasn't proved that it helps patients.

And this morning, I heard details about yet another disappointing result. This was a study of people in Colombia who carry a gene that pretty much guarantees they will develop Alzheimer's at an early age. And they got an anti-amyloid drug called crenezumab for five years or more - that's a long time - but it didn't work. The drug might have helped a little, but not enough to achieve statistical significance.

SHAPIRO: There's also been some talk about research into these drugs that appears to be fraudulent. What's going on there?

HAMILTON: Yeah. So there was an investigative report in the journal Science looking at studies involving this researcher from the University of Minnesota. Those studies suggested that one particular form of amyloid causes memory problems in rodents. But now it looks like data from those papers was altered. The report in Science says this calls into question the whole idea that amyloid is important in Alzheimer's. But the scientists I've talked to here - they all disagree.

You might expect that researchers who do amyloid research would see it that way, so I talked to somebody who was not at the meeting. His name is Karl Herrup at the University of Pittsburgh. He's a longtime critic of what's known as the amyloid hypothesis, but he doesn't buy the idea that this one study led the field astray. Here's what he told me.

KARL HERRUP: That there was fraud I think is very clear. The paper in Science documents that very, very well. But the evidence in those papers was really tangential to the field.

HAMILTON: Yeah, so his point is that there are hundreds and hundreds of amyloid studies out there, and no single piece of research can have that much influence.

SHAPIRO: Well, if amyloid drugs are not the answer, what is?

HAMILTON: Well, people are looking at several possibilities that they talked about here. One is drugs that go after these tangles that appear inside of neurons of people with Alzheimer's. There are several drugs being tested that try to get rid of these tangles. Another option is drugs that target inflammation in the brain - another sign of Alzheimer's. And today I heard from researchers who presented a study of a drug that helps brain cells metabolize sugar. It acts a bit like a diabetes drug, and there are some signs that this drug can actually slow down memory loss.

SHAPIRO: Well, is there anything that people who might be concerned about developing Alzheimer's can do right now when there are not good drugs on the market to treat or prevent it?

HAMILTON: Exercise. There are now a whole lot of studies suggesting that people who exercise are less likely to develop Alzheimer's. And today I heard about a new study that treated exercise as if it were a medicine. It's called the EXERT Study. And it looked at about 400 people - these are sedentary people with mild cognitive impairment, which is the earliest stage of Alzheimer's. And they were all prescribed YMCA memberships and a personal trainer for a year.

So typically, people with mild cognitive impairment get worse every year. But in this study, they didn't. And what's really interesting is that the benefit was not only for people who did aerobic exercise, but it also worked for people who just went and did stretching and flexibility exercises on a really regular basis.

SHAPIRO: NPR's Jon Hamilton reporting there from the Alzheimer's Association International Conference in San Diego. Thanks a lot.

HAMILTON: My pleasure, Ari. Transcript provided by NPR, Copyright NPR.

Jon Hamilton is a correspondent for NPR's Science Desk. Currently he focuses on neuroscience and health risks.