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Time to rethink low-dose aspirin therapy?

Posted by medconsumers on June 20, 2012

Here’s a new slant on the daily low-dose aspirin routine followed by millions of Americans: You might want to stop, if you don’t have heart disease or are at low risk for it. Why? The chance of having a rare but serious side effect from aspirin therapy may be higher than the chance of avoiding a heart attack or stroke.   And this goes for people with diabetes.

These new findings, published online first by the Journal of the American Medical Association, call into question the current thinking about the safety of low-dose aspirin therapy. They also brought to mind an interview I did years ago when doctors were telling us—in the media and in person—that statins are safer than aspirin. I was skeptical about the purported safety of statins because these cholesterol-lowering drugs were relatively new at the time. What’s more, the comparison didn’t seem convincing. After all, it took medical science a hundred years to understand the risks of aspirin.

But the research physician I was interviewing pointed out that all the aspirin vs. placebo clinical trials showed that—no matter how low the aspirin dose—there were always more cases of brain or gastrointestinal bleeding in the study participants on aspirin.

Naturally, I checked his contention and found that the smallest aspirin dose studied to date was a trial that included healthy postmenopausal women taking 100 mg aspirin every other day. And indeed, there were more cases of serious bleeding in the women on aspirin than in those on a placebo.

That’s my backstory  for the new evidence against low-dose daily aspirin use in people without heart disease. Surprisingly, a new study found that the incidence of major bleeding leading to hospitalization is much higher than has been reported in clinical trials. Significantly, this new finding is not based on people who took part in clinical trials.

The study was conducted in the Puglia region of Italy where researchers had access to the medical records of all its citizens. They singled out 186,425 people, aged 30 to 95 years, on low-dose aspirin therapy and matched them with an equal number of people of similar ages and health who were not on aspirin therapy. Both groups had equal number of diabetics (about 15%).  All were followed for nearly six years.

Here are the results: There were bleeding-related hospitalizations in 3,369 of the people not on aspirin therapy, and in 3,538 of those on aspirin therapy. Put another way, 169 more cases of serious bleeds in those on aspirin.

This study provides a more accurate, real-world assessment of aspirin therapy’s harm than a clinical trial because people who volunteer for research are typically younger and healthier than the general population. And those with multiple chronic conditions are usually excluded.

From the medical records of people hospitalized for severe bleeding incidents, the Italian researchers were able to identify those most likely to be affected. Men, for example, are more likely than women. So are people with previous hospital admissions for gastrointestinal problems, those on other drugs known to cause bleeding (e.g., Coumadin, Plavix), and everyone over age 70.

The editorial that accompanied this study made it clear that aspirin therapy’s benefit outweighs its harms for people with heart disease. “For 6 major vascular events [e.g., stroke, heart attack] prevented, approximately1 major bleeding event would occur; therefore, the value of aspirin for secondary prevention is not disputed.”   (Click here for another estimate)

As for everyone else—the people who don’t have heart disease—the Italian researchers described two noteworthy aspects of their findings:  It has long been known that people with diabetes have a increased risk (36%) of bleeding, but this is the first study to show that aspirin had no effect. Low-dose aspirin therapy neither decreased or increased the bleeding risk in diabetics.

The other important finding involves statins. (Yes, I’ve come full circle to statins and aspirin). About one-fourth of all people in this study were taking statins, which appeared to have a protective effect against aspirin, say the researchers, citing a “substantially lower risk of both gastrointestinal and intracranial hemorrhages associated with the use of statins.”  They cite several previous studies that confirmed this protective effect.

But things are not so clear for brain bleeds. The researchers cite a large, randomized trial published last year that suggested statins may increase the risk of intracranial hemorrhage [emphasis added].”The take-home message:  your risk of stroke or heart attack has to be high enough to warrant the newly identified higher risk of major bleeding. But you might need someone with an advanced degree in biostatsitics, rather than a family doctor, to help you sort things out.

To me, this is a cautionary tale relevant to all “preventive” medicines. If it took this long to understand aspirin, how long will it take to learn the full-story on the harms of newer drugs like Plavix and Fosamax that people are expected to take daily to cut their chances of heart attack or a fracture.

And keep this in mind: Aspirin therapy is for life, but this study (like most clinical trials) lasted less than six years.

Maryann Napoli, Center for Medical Consumers©

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Most drugs don’t work in most people  Read how doctors, journalists, and consumers are misled by the way drug-effectivess statistics are presented in medical journals.

3 Responses to “Time to rethink low-dose aspirin therapy?”

  1. Robert Kelman said

    “Here are the results: There were bleeding-related hospitalizations in 3,369 of the people not on aspirin therapy, and in 3,538 of those on aspirin therapy. Put another way, 169 more cases of serious bleeds in those on aspirin.”

    This appears to be statistically insignificant. Is it?

    rob.calm

    • Here’s what the authors of this study wrote: “The cumulative proportion of patients developing major bleeding events during follow-up according to diabetes status and use of aspirin was estimated by life table methods and log-rank tests were reported.Pvalues were 2-sided, and values of .05 or less were considered statistically significant. All statistical analyses were performed using SASversion 9.1(SAS Institute Inc).”

  2. Cate Shea said

    I wonder whether this finding has anything to suggest about those of us who are taking daily doses of warfarin for year after year? I have often wondered whether it is really necessary to be doing this.

    Then, there are the drugs new to the market, designed to replace warfarin. My rule is never to take a drug that has not been on the market at least five, if not ten, years!

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