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Aspirin for primary prevention: yes or no?

AIM
To assess benefit versus harm of aspirin for cardiovascular disease (CVD) primary prevention by age group, gender and risk category and to interpret these results in light of current New Zealand CVD risk assessment and management guidelines.


METHODS
Rates of benefit (avoided vascular events) and harm (additional major extracranial bleeds) for each gender and age group were calculated from data from the six randomised controlled trials included in the Anti-Thrombotic Trialists' (ATT) Collaboration meta-analysis. These rates were applied to CVD risk categories to calculate the net benefit or net harm likely to occur from the use of aspirin in primary prevention of CVD as monotherapy and when added to lipid and blood pressure-loweringtherapies.


RESULTS
Benefits of aspirin monotherapy outweigh the harms for both men and women aged up to 80 years with calculated five-year CVD risk >15% in primary prevention. Harm may outweigh benefit for primary prevention for those over 80 years. For men 70-79 years the benefit of aspirin in primary prevention is marginal when added to lipid and blood pressure-lowering therapies.


DISCUSSION
The recent ATT Collaboration meta-analysis has raised doubts about the relative safety of aspirin in primary prevention of CVD. However, modelling by risk category and age group suggests that current guidelines are justified in recommending aspirin for primary prevention of CVD in those with five-year CVD risk > or = 15% up to the age of 80 years. For men 70-79, consider lipid and blood pressure-lowering therapies first then reassess whether aspirin adds additional net benefit.