According to a meta-analysis published early online in the Archives of Internal Medicine, despite important reductions in nonfatal MI, aspirin prophylaxis in people without prior CVD does not lead to reductions in either cardiovascular death or cancer mortality.

Researchers conducted the systematic review and meta-analysis to assess the safety and efficacy of aspirin on vascular and nonvascular outcomes in primary prevention. A total of 9 randomised, placebo-controlled trials involving at least 1000 patients per trial, and reporting on cardiovascular disease, nonvascular outcomes, or death were included in the analysis. Risks vs. benefits were evaluated by comparing CVD risk reductions with increases in bleeding. The following results were reported:

• During a mean (SD) follow-up of 6.0 (2.1) years involving over 100,000 participants, aspirin treatment reduced total CVD events by 10% (OR, 0.90; 95% CI, 0.85-0.96; number needed to treat, 120), driven primarily by reduction in nonfatal MI (OR, 0.80; 95% CI, 0.67-0.96; number needed to treat, 162).

• There was no significant reduction in CVD death (OR, 0.99; 95% CI, 0.85-1.15) or cancer mortality (OR, 0.93; 95% CI, 0.84-1.03), and there was increased risk of nontrivial bleeding events (OR, 1.31; 95% CI, 1.14-1.50; number needed to harm, 73).

The researchers conclude that “only modest benefits of aspirin treatment on nonfatal MI and total CVD events in primary prevention were seen, while the effect on cancer mortality was non-significant. Furthermore, because the benefits of aspirin treatment were accompanied by a significant increase in risk of bleeding, further study is needed to identify subsets of participants having a favourable risk to benefit ratio for aspirin use in primary prevention and/or involving more high-risk participants. In the absence of such information, a reappraisal of current guidelines appears to be warranted, particularly in countries where a large number of otherwise healthy adults are prescribed aspirin, since a significant proportion of them may develop bleeding complications.”

A related editorial discusses the study and several press agencies have also reported this study (please see links below). Furthermore, the Royal Pharmaceutical Society has also issued a press statement advising patients who are currently self-medicating with low dose aspirin for primary prevention to consult their pharmacist before they stop aspirin.