Aspirin May Increase Internal Bleeding Risk

Patients without cardiovascular disease (CVD) may reduce their risk of cardiovascular events by taking aspirin, but in doing so could put themselves at risk of internal bleeding, according to a new study.

Researchers queried PubMed and Embase for randomized clinical trials including at least 1,000 patients without CVD who committed to at least 12 months of follow-up. Primary outcomes were cardiovascular (a composite of cardiovascular mortality, nonfatal myocardial infarction, and nonfatal stroke) and bleeding (any major bleeding as defined by the individual studies).

Final analysis included 13 trials with 164,225 total patients (mean age, 62 years; 53% female) and 1,050,511 patient-years of follow-up; 19% of patients had diabetes. Compared with no aspirin, patients taking aspirin had greatly reduced cardiovascular outcomes (57.1 per 10,000 patient-years with aspirin and 61.4 per 10,000 patient-years with no aspirin) (hazard ratio [HR], 0.89 [95% credible interval, 0.84-0.95]; absolute risk reduction, 0.38% [95% CI, 0.20%-0.55%]; number needed to treat, 265). However, patients using aspirin also had greater incidence of major bleeding events (23.1 per 10 000 participant-years with aspirin and 16.4 per 10 000 participant-years with no aspirin) (HR, 1.43 [95% credible interval, 1.30-1.56]; absolute risk increase, 0.47% [95% CI, 0.34%-0.62%]; number needed to harm, 210).

One of the study’s limitations pertained to the diabetes subgroup, for which cardiovascular and bleeding outcomes were poorly reported. Another was that each study did not have the exact same primary outcome. Additionally, daily aspirin doses varied in each study, from 50 mg to 500 mg. Finally, some studies began as early as the 1970s, while some started after 2000. “Increasing adoption of additional primary prevention strategies, such as risk factor modification and development of public health initiatives, may limit the applicability of earlier studies to current practice,” the researchers noted.

Still, the study authors concluded that their findings “may inform discussions with patients about aspirin for primary prevention of cardiovascular events and bleeding.”

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Source: JAMA