Updated screening technologies and more widespread use of statins have rendered aspirin ineffective for the primary prevention of CVD, according to a study published in Family Practice.
Co-authors Frank Moriarty, of the Royal College of Surgeons in Ireland, and Mark H. Ebell, of the University of Georgia, said that nearly half of adults aged 70 and up report taking daily aspirin as a way to reduce their risk of chronic disease, even if they have no history of CVD or stroke. The over-the-counter drug is one of the U.S.’s most popular medications, used by an estimated 40% of adults in the country.
Older studies dating back 30 years supported regular use of aspirin for primary prevention of CVD, but Moriarty and Ebell said in their paper that more recent clinical trials have failed to replicate those benefits. They compared the results of aspirin studies that recruited patients between 1978 and 2002 with those that enrolled patients from 2005 onward.
The researchers’ individual patient data (IPD) analyses of older studies included 95,456 patients who took aspirin for CV prevention and 25,270 who took it for cancer mortality. Moriarty and Ebell said the older patients’ characteristics differed from those of the 61,604 patients enrolled in newer studies, who were on average older, somewhat less likely to smoke and more likely to have type 2 diabetes than their counterparts in older trials.
The authors reported relative risks for vascular outcomes for older versus newer studies, respectively, as follows:
- Major adverse cardiac events (MACE): 0.89 vs. 0.93
- Fatal hemorrhagic stroke: 1.73 vs. 1.06
- Any ischemic stroke: 0.86 vs. 0.86
- Any MI: 0.84 vs. 0.88
- Nonfatal MI: 0.79 vs. 0.94
The duo found that, as in older studies, recent trials of aspirin for primary prevention found no mortality benefit and a significant increase in patients’ risk of major hemorrhages. They couldn’t establish a connection between aspirin and a reduction in cancer deaths or non-fatal MIs, though.
In all, Moriarty and Ebell wrote that per 1,200 people taking aspirin for primary prevention for five years, there will be four fewer MACEs, three fewer ischemic strokes, three more intracranial hemorrhages and eight more major bleeding events. The authors said most older trials recruited patients prior to 2000, and since then, cholesterol-lowering drugs, CVD management and proactive cancer screenings have become more popular and efficient.
“The good news is that the incidence of cardiovascular disease and colorectal cancer are decreasing due to better control of risk factors and screening, but that also seems to reduce the potential benefit of aspirin,” the researchers said in a statement.
It’s not the first time the utility of aspirin as a means of primary prevention has been questioned, even this year. A major study published in JAMA Neurology this May concluded the bleeding risks of daily aspirin outweighed its benefits in the general population, and in March the American Heart Association and American College of Cardiology downgraded the drug in their primary prevention guidelines.
Two polls—one conducted by researchers at Fairleigh Dickinson University and another by pharmaceutical company Bayer—revealed that most people who take baby aspirin don’t have a chronic illness and that 26% of heart attack survivors are confused about the role the drug plays in secondary MI prevention.
At the time Bayer’s study was published, Rose Coppolecchia, U.S. Director, Medical Affairs Cardiology, Consumer Health at Bayer, said mixed media coverage of aspirin makes it difficult for people to discern the truth about its efficacy.
“Many people are confused by the recent news around who should take aspirin,” Coppolecchia said. “For heart attack survivors, confusion is especially concerning since taking aspirin regularly, as directed by a doctor to help prevent another heart attack (or ischemic stroke), can be a life-saving preventative treatment.”