Importance: A decision to initiate aspirin therapy for primary prevention of cardiovascular disease (CVD) requires consideration of both treatment benefits and harms. The most significant harm associated with aspirin is major bleeding, yet there is a paucity of data on bleeding risk in suitable community populations.
Objective: To determine the risk of major bleeding among people without CVD who are not receiving antiplatelet therapy.
Design, setting, and participants: Prospective cohort study of 359 166 individuals aged 30 to 79 years receiving primary care in New Zealand who had CVD risk assessment between 2002 and 2015. Participants were censored at the earliest date on which they had a first major bleeding event, died, or met any baseline cohort exclusion criteria or the study end date of December 31, 2015. Analyses were repeated after excluding people with medical conditions associated with increased bleeding risk (non-high-risk cohort; n=305 057) and after further excluding people receiving other medications associated with increased bleeding risk (nonmedication cohort; n=240 254).
Exposures: Sex and age group in 10-year bands from 30 to 79 years.
Main outcomes and measures: Risk of a major bleeding event (hospitalization or death associated with bleeding); nonfatal gastrointestinal tract bleeding; and gastrointestinal tract bleeding-related case fatality.
Results: Mean participant age was 54 years (SD, 10 years), 44% were women, and 57% were European. Among the 359 166 individuals in the baseline cohort, 3976 had a major bleeding event during 1 281 896 person-years of follow-up. Most had gastrointestinal (GI) bleeding (n=2910 [73%]). There were 274 fatal bleeding events (7%), of which 153 were intracerebral. The risk of a nonfatal GI bleeding event per 1000 person-years was 2.19 (95% CI, 2.11-2.27), 1.77 (95% CI, 1.69-1.85) and 1.61 (95% CI, 1.52-1.69), in the baseline, non-high-risk, and nonmedication cohorts, respectively. Case fatality associated with GI bleeding was 3.4% (95% CI, 2.2%-4.1%), 4.0% (95% CI, 3.2%-5.1%), and 4.6% (95% CI, 3.6%-6.0%) in the baseline, non-high-risk, and nonmedication cohorts, respectively.
Conclusions and relevance: In a population not receiving antiplatelet therapy, the annual risk of major bleeding events and nonfatal major bleeding was estimated. These findings could inform population-level guidelines for primary prevention of CVD.