New guidelines question once-a-day aspirin intake

Millions of people have been taking low doses of aspirin to prevent heart attacks and strokes, but now there's new thinking that may change that.

Some medical experts, both in the United State and in the U.K., have come to the conclusion that too many people have been taking low-dose aspirin. New guidelines by the U.S. Preventive Health Services Task Force are giving more clarity about who should be taking it.

Dr. Jon Hallberg, medical analyst for All Things Considered, spoke to MPR's Tom Crann about the guidelines and why they've changed.

Tom Crann: Who was taking aspirin previously under these recommendations?

Dr. Jon Hallberg: A lot of people, and the last time the recommendations were updated in 2002, it said that men over 40 and women over 50 who were at higher risk -- and it was sort of vague as to what that meant -- could or should be taking low-dose aspirin. So we were really preaching that gospel and putting people on aspirin, and it turns out probably millions of people are on it that don't need to be on it.

What does aspirin actually do? A lot of people think it's a blood thinner, but it isn't really, is it?

That's right. We always use that term, but that sort of implies that we're diluting the blood, and that's not the case at all. It's making the blood less sticky. There are elements in blood called platelets, and this is sort of anti-platelet therapy. It doesn't stop them from working altogether, but it reduces the effectiveness of that, so that you're less likely to have a clot. And a clot is what causes the majority of heart attacks and the majority of strokes.

We're talking about a low-dose or baby aspirin, and it was marketed that way for adults. What are the risks even with this low dose of aspirin?

Because it makes the blood less sticky, we are more likely to bleed. And if people have a tendency toward ulcers in the stomach, for example, they could have bleeding ulcers.

Aspirin has two effects. It has the anti-platelet part, but it also is an anti-inflammatory medication. And prostaglandins, the sort of chemical that cause inflammation, also protects the stomach lining. Aspirin can't tell the difference between those two functions, and so it makes the stomach more susceptible to its own hydrochloric acid, and it can cause great irritation.

You were taking low-dose aspirin and then you stopped. Why?

I was in my early 40s. I was following the guidelines, figuring that as a guy over 40 I was at higher risk, even though if I do the calculation, I really wasn't. I thought, 'For a third of a penny a day, why not do this?'

But after about a year of the therapy, I started getting reflux. My stomach was more irritated than it should've been. I stopped the medication, and the symptoms went away.

Is the concern, then, that the risk of stomach inflammation is greater than the benefit of the aspirin?

Exactly. What we're trying to do with all of these people is do something called primary prevention. We're trying to prevent a stroke or heart attack from happening. The trouble is you don't want the intervention, the aspirin use, to cause any problems. Frankly, it's already a pretty low-risk event for most of us, of having a stroke or heart attack in our younger ages. And many people in their 50s or 60s or even 70s are at relatively low risk. So you don't want to do something that's going to cause more harm than good.

When we talk about high risk for heart attack and stroke, what does that mean?

There's some debate about this. To help us get a handle on this and not go with a gut level feeling, tools have been developed. And these tools are basically calculators that calculate your risk for having a stroke or a heart attack. And they're easily available online.

I have one actually on my iPhone that I tap into when I'm meeting with patients. And you plug in things like gender, age, blood pressure, cholesterol levels, and those kinds of things. And it gives you a range. It'll say, 'This person has a 7 percent risk of having a heart attack in the next 10 years.' That's a 0.7 percent risk per year. That's a relatively low risk.

And then high risk starts to kick in around 10 or even 20 percent, and that's where some of the debate is. If someone has a 20 percent risk of having a heart attack, they're high risk. In that case, the benefits probably out weigh the risks of being on an aspirin a day.

There's also a difference here in the recommendations for men and women. What's the difference, and why?

This is where the U.S. researchers and the British authorities differ a little bit. The studies suggest that men probably benefit more from aspirin used to prevent heart attacks, and women probably benefit more from taking aspirin to prevent stroke.

And why is that?

Well, it's just based on research. It's basically what they found. And there's some thought now that, 'Is it possible that platelets act differently in men and women? Is there a sort of genetic difference between the two groups?' And I think that's something that's going to be explored. I mean there seems to be some fundamental differences. The Brits say no. The Americans say yes.

So, someone comes into the clinic, and they wonder, 'Should I be taking this aspirin dose? Am I at risk?' What goes into that calculation?

We'll certainly look at lifestyle and family history, but then I'll actually pull out a calculator and plug in the numbers, and see what the total score is. Based on that, we'll have a further conversation. It's never a slam dunk, but I think that if someone's at high risk, we'll talk about putting them on aspirin.

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