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How to approach prescribing aspirin for primary prevention

Recently published trials offer more evidence to aid in physician decision-making regarding use of aspirin for primary prevention, according to a paper published in Annals of Internal Medicine.

“Defining the role of aspirin in patients with no history of cardiovascular events (primary prevention) is challenging. Aspirin can have important benefits, including preventing cardiovascular events and possibly reducing the incidence and mortality of some types of cancer,” Michael Pignone, MD, MPH, chair of the department of medicine in the Dell Medical School at the University of Texas, and Darren A. DeWalt, MD, MPH, chief of the division of general medicine and clinical epidemiology at the University of North Carolina School of Medicine, wrote.

“However, it can also have important harms, including increasing risk for gastrointestinal bleeding and possibly intracerebral hemorrhage,” they added.

Numerous large trials have been conducted, but evidence regarding aspirin for prevention is difficult to interpret due to the close balance of benefits and harms, according to Pignone and DeWalt.

When deciding to prescribe aspirin for primary prevention, physicians should consider new evidence, they wrote, pointing to the ASPREE (Aspirin in Reducing Events in the Elderly) and ASCEND (A Study of Cardiovascular Events in Diabetes) trials.

ASPREE was a large trial involving 19,114 patients aged 70 years or older who were generally healthy. In the study, patients receiving aspirin showed smaller nonstatistically significant effects on cardiovascular events compared with those receiving placebo (HR = 0.95; 95% CI, 0.83-1.08). Conversely, there was an increased risk for major bleeding (HR = 1.38; 95% CI, 1.18-1.62) with aspirin use similar to that in prior trials. All-cause mortality and cancer mortality also increased.

“These results move the benefit–harm calculation toward harm for initiating aspirin therapy for primary prevention in older adults but do not inform treatment of patients who were receiving aspirin before age 70 years,” Pignone and DeWalt wrote.

The ASCEND trial included 15,480 patients aged 40 years or older with diabetes and no previous CVD. In the study, patients receiving aspirin showed a modest decrease in cardiovascular events (rate ratio = 0.88; 95% CI, 0.79-0.97) and a modest increase in major bleeding risk (rate ratio = 1.29; 95% CI, 1.09-1.52), compared with those receiving placebo. The researchers observed no effect on cancer with aspirin use. There was inconclusive evidence to determine an association between aspirin use and all-cause mortality.

Regarding this new evidence, Pignone and DeWalt suggest that physicians consider the following recommendations to guide decision-making for using aspirin as primary prevention:

• In most adults older than 70 with or without diabetes, aspirin therapy should not be initiated for primary prevention.
• Middle-aged adults should be prescribed aspirin therapy based on cardiovascular risk.
• For adults younger than 70 years with persistent elevated cardiovascular risk despite using appropriate therapies, aspirin may be offered as an additional risk reducing therapy if there is no increased risk for bleeding.
• Decision-making should be shared between the physician and patient based on the patient’s values and preferences.
• There is no clear evidence to support withdrawing aspirin at age 70 years if a patient already initiated it for primary prevention at an earlier age.

“Although much is written about aspirin and many patients take it without a second thought, the overall magnitude of net benefit is likely small,” Pignone and DeWalt concluded. “However, aspirin therapy should be considered after use of smoking cessation, statins and blood pressure control. Additional follow-up from these trials and others will help us to better understand whether beneficial effects on cancer are confirmed, which would tilt the decision toward aspirin use.” – by Alaina Tedesco

Disclosures: Pignone reports being a former member of the U.S. Preventive Services Task Force. DeWalt reports receiving grants from PCORI ADAPTABLE Study.