Review: aspirin was effective for primary prevention of stroke in women and MI in men but increased major bleeding
Q What are the benefits and risks of aspirin for primary prevention of cardiovascular (CV) disease in women and men?
Medline (1966 to March 2005), bibliographies of retrieved articles, and monitoring of major scientific meetings.
Study selection and assessment:
randomised controlled trials (RCTs) that allocated participants to aspirin or a control group for primary prevention of CV disease and outcomes included CV mortality, myocardial infarction (MI), and stroke. Quality of individual studies was assessed based on allocation concealment, follow up, and objectivity of outcome assessments. 6 RCTs (51 342 women and 44 114 men, mean age 55–65 y) met the selection criteria. Aspirin dosage ranged from 100 mg every other day to 500 mg daily. Patient follow up was >95% in all trials, and duration of follow up ranged from 3.6 to 10.1 years.
composite endpoint of any major CV event (CV mortality, non-fatal MI, or non-fatal stroke), individual components of the composite endpoint, all cause mortality, and major bleeding.
Both women and men in the aspirin group had a lower risk of the composite of major CV events and a higher risk of major bleeding than the control group (table). Women in the aspirin group had a lower risk of stroke than those in the control group, and men had a lower risk of MI (table). No differences were found for the remaining outcomes.
Aspirin for primary prevention of cardiovascular disease reduced the risk of overall cardiovascular events in both men and women but increased the risk of major bleeding. Aspirin reduced the risk of stroke in women and myocardial infarction in men.
- David R Thompson, RN, PhD, MBA, FRCN, FESC
This sex-specific meta-analysis by Berger et al of more than 50 000 women and 40 000 men enrolled in 6 RCTs of low dose aspirin for primary prevention of CV events showed that aspirin therapy reduced the risk of overall CV events, but increased the risk of major bleeding, in both sexes. It also reduced the risk of stroke (but not MI) in women and MI (but not stroke) in men. The authors offer several possible explanations for the differences in cardioprotection observed between the sexes, such as differences in aspirin metabolism and resistance, as well as event rates of stroke and MI. Indeed, a recent study reported sex differences in platelet reactivity and response to low dose aspirin therapy.1 Also, most women in this meta-analysis were participants in the Women’s Health Study,2 and so the findings primarily represent those of that study. Other possible explanations for the differences include important sex differences in CV disease prevention, presentation, treatment, morbidity, and mortality. For example, aspirin may have lowered the risk of stroke in women simply because they have a higher risk of stroke than MI. Also, the Women’s Health Study may have had insufficient statistical power with respect to the risk of MI. Finally, women tend to develop heart disease about 10–15 years later than men, which may explain why, in the Women’s Health Study, aspirin seemed to result in benefits in all major CV endpoints, including stroke and MI, only in women ⩾65 years of age.
The review shows that aspirin is effective, but careful consideration needs to be given to the risk it entails. It also highlights some issues that have implications for nurses and other health professionals, as well as lay people. For example, in countries where aspirin is available as an over-the-counter drug, patients who have an increased risk of bleeding should consult with a health professional before initiating aspirin therapy.
For correspondence: Dr D L Brown, SUNY-Stony Brook Health Sciences Center, Stony Brook, NY, USA.
Source of funding: not stated.