Daily aspirin DOESN'T protect against heart attack or stroke in healthy older people |
Norman Swan: It's been estimated that around the world there are millions of people who are otherwise healthy, have never had a heart attack or stroke, are not at high risk of bowel cancer, yet who take aspirin on a daily basis, convinced that it's going to help them. Well, the evidence for the largest ever study in this area suggests not. A huge trial called ASPREE involving healthy Australians and Americans aged over 70 given low-dose aspirin for five years has found no benefits and some harms. The research was led by Professor John McNeil of the School of Public Health and Preventative Medicine at Monash University who I spoke to before we went to air.
Welcome to the Health Report John.
John McNeil: Thank you Norman.
Norman Swan: It's pretty impressive, three papers in the New England Journal. What sparked the study? Because it was Australian motivated, even though it occurred in the United States as well.
John McNeil: I think we've been aware since the 1990s that there is an evidence gap that many millions of people take aspirin every morning, and the evidence base, particularly for those who haven't had a heart attack or a stroke or have no other medical reason to be taking it, the evidence just isn't there.
Norman Swan: So what did you do in this study?
John McNeil: We recruited 19,100 people from the United States and Australia, 16,700 were from Australia, we followed them for an average of 4.6 years, and half of them took aspirin and half of them took placebo.
Norman Swan: And what were you looking for, what were your endpoints?
John McNeil: Well, the endpoint here was disability-free survival which is a measure of how long elderly people stay healthy.
Norman Swan: But how did you measure that?
John McNeil: By measuring how long it took for people to remain healthy without having a permanent physical disability or developing dementia.
Norman Swan: And what did you find?
John McNeil: Well, we found three things. Firstly, low-dose aspirin did not appear to increase survival.
Norman Swan: Disability-free survival or survival?
John McNeil: Disability-free survival and survival. And it also didn't prevent heart attack or stroke. I think I should emphasise that this study was done in people who had never had a heart attack or a stroke because people who have routinely take aspirin under very strong evidence to prevent them having another one.
Norman Swan: So we're talking about healthy people recruited who were over 70 on average, is that right?
John McNeil: That's right, the average age was 74.
Norman Swan: What about cancer? A lot of people take aspirin to prevent cancer and there is some randomised trial evidence that aspirin can prevent cancer.
John McNeil: Yes, this was a surprising finding in our study. There were numerically more people dying of cancer in the aspirin arm than in the placebo arm. This was a relatively small effect. It wasn't statistically significant once we adjusted for the multiple comparisons that we were making, and it hasn't been seen in other large clinical trials. So we are suspending judgement as to what its significance really means.
Norman Swan: And what were the complications and the side-effects?
John McNeil: Well, we had the usual side-effect of bleeding. We took a lot of care in the management of bleeding because older people are more inclined to bleed, and aspirin enhances that effect. We certainly had an increase in haemorrhage in the people taking aspirin.
Norman Swan: Previous studies have suggested and we had this on the Health Report, I think it was last year, suggesting that if there was a haemorrhage risk it was early on and that settled down later.
John McNeil: We looked at this, but we couldn't find that. According to our data, the risk of haemorrhage just kept going.
Norman Swan: We had a story not so long ago on the Health Report suggesting that the effect of low-dose aspirin is actually only there in people who weigh 70 kg or less and that if you want to get an effect from aspirin you should be on a higher dose, like 325 mg or even 600.
John McNeil: We've had a brief look at that and we couldn't find that in our older people.
Norman Swan: What about dementia?
John McNeil: Aspirin appeared to have no effect at all on dementia.
Norman Swan: But four years is not a long time to develop dementia. Did you measure cognitive decline?
John McNeil: Yes, we measured cognitive decline very carefully and we haven't analysed all the data yet but certainly the number of people who were diagnosed with dementia was the same on each arm. But that raises a very important issue because we will be following the people who participated in ASPREE over the long term to see if there is a difference in the incidence of dementia or cancer that appears later. And we know that there's been evidence that cancer preventative effect does take four or five years before it becomes evident. That's one of the reasons why we have been very keen for our ASPREE participants throughout both countries to continue to be involved and let us follow them up.
Norman Swan: If you have haemorrhage or you have side-effects like gastric upset or something like that from aspirin, the people who are taking the real thing might have dropped out more than people in the placebo. That could have affected the results.
John McNeil: We did a lot of testing of how many people were taking the aspirin, we counted their pill bottles and so on, and we found that basically there was very good compliance with the medication on both arms of the study.
Norman Swan: Could this be a phenomenon of as we are getting older we are actually not necessarily ageing, we're actually living longer younger, and we are getting less heart disease. Was this population too young, paradoxically, even though they were 75, were they actually too young to get an effect? Because 75 is like the new 50, as they say.
John McNeil: That's an interesting question. We followed people whose commencement average age was 74, and whose final average age was nearly 79. So that's following people through a reasonably long period. We had a number of people who were over 80 years of age. And as far as we could tell there wasn't a really big difference between the impact of aspirin and any of these ages.
Norman Swan: So if somebody is taking aspirin now, they are entirely healthy, they've never had heart disease, they've not had bowel polyps, which is another reason why some people might take aspirin to prevent the polyps turning into cancer or new polyps emerging, and they are on aspirin, should they just stop?
John McNeil: Look, we are not recommended this at this point. People taking aspirin, take it, for three reasons. Some of course, as you said, have had a heart attack or a stroke or something similar in the past, and they should definitely be on aspirin because the evidence is strong. And then there's others who have been put on aspirin by their doctors for a range of other reasons, and they should continue as well, certainly not stop without getting advice from their doctor. But then there's the third category who may have just decided, they've read somewhere, they're perfectly healthy, they think it's a good idea, the results of ESPRIT will lead these people to reconsider whether that's a good idea.
Norman Swan: Just finally, do we know the numbers of people who are taking aspirin unnecessarily?
John McNeil: We know that it's much more common in the United States where about 40% of the people entering ASPREE had been taking aspirin in the past. In Australia the number was quite a lot less, but it still adds up to many millions of people around the world.
Norman Swan: John McNeil, thank you very much for joining us.
John McNeil: Thank you Norman.
Norman Swan: Professor John McNeil is head of the School of Public Health and Preventative Medicine at Monash University in Melbourne. So if you've had a heart problem like a heart attack, angina, stents or a bypass or a stroke or are at high risk of bowel cancer because of multiple polyps or a strong family history, then you should be on aspirin unless there's good reason not to.
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