Background: The net benefit of aspirin in prevention of
CVD and nonvascular events remains unclear. Our objective
was to assess the impact (and safety) of aspirin on vascular
and nonvascular outcomes in primary prevention.
Data Sources: MEDLINE, Cochrane Library of Clinical
Trials (up to June 2011) and unpublished trial data
from investigators.
Study Selection: Nine randomized placebocontrolled
trials with at least 1000 participants each, reporting
on cardiovascular disease (CVD), nonvascular outcomes,
or death were included.
Data Extraction: Three authors abstracted data. Studyspecific
odds ratios (ORs) were combined using randomeffectsmeta-analysis.Risksvsbenefitswereevaluatedbycomparing
CVD risk reductions with increases in bleeding.
Results: 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
reductioninnonfatalMI (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 cancermortality
(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). Significant
heterogeneity was observedfor coronary heart disease and
bleeding outcomes, which could not be accounted for by
major demographic or participant characteristics.
Conclusions: 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. Because the benefits arefurther offset by clinically
important bleeding events, routine use of aspirin for
primary prevention is not warranted and treatment de