Aspirin discontinuation in CVD prevention is associated with increased CV risk
Low-Dose Aspirin Discontinuation and Risk of Cardiovascular Events: A Swedish Nationwide, Population-Based Cohort StudySundström J, Hedberg J, Thuresson M, et al. - Circulation. 2017;136:1183-1192
Guidelines recommend low-dose aspirin for the secondary prevention of CVD, however there are discontinuation rates of up to 30% and poor compliance in up to 50% of patients [1,2]. The discontinuation of aspirin in secondary prevention has been associated with a higher CV risk shortly after discontinuation [3,4]. Aspirin discontinuation is common when bleeding occurs or major surgery is necessary, however, in settings other than surgery or bleeding the effects of aspirin discontinuation are not known. Moreover, the benefit of aspirin use in primary prevention is under investigation.
In this study, the associations of aspirin treatment persistence patterns and aspirin discontinuation with the CV risk was evaluated, in a large nationwide cohort of patients on long-term low-dose aspirin therapy for primary and secondary prevention between 2005 and 2009. Eligible patients were older than 40 years of age, and had ≥80% adherence during the first year of treatment, had no history of cancer at baseline, and no CV event or death during the first year of aspirin treatment, based on the Swedish inpatient and cause-of-death register.
A major bleeding or a surgical procedure during the study corresponded to a 3-month refractory period from the time at risk, during which person-time was not counted and outcomes were not considered.
- During a median of 3.0 years of follow-up (range: 0.002–3.5 years), corresponding to 1 491 369 person-years (PY) at risk, 62 690 CV events occurred (incidence rate: 42.0 per 1000 PY at risk). 19 978 PY were excluded from the analyses because of surgical procedures and major bleeding events.
- Patients on persistent aspirin treatment had the lowest incidence of CV events. Patients who had discontinued aspirin had a 37% higher rate of CV events, corresponding to an absolute risk increase of 13.5 events per 1000 PY at risk. On average, 1 of every 74 patients who discontinued aspirin had an additional CV event in 1 year.
- In patients receiving aspirin for secondary prevention, discontinuing aspirin was associated with a 46% higher rate of CV events than continuing on aspirin, corresponding to an absolute risk increase of 28.0 per 1000 PY at risk, or an additional CV event per year in 1 of every 36 patients who discontinued aspirin.
- In patients who were probably using aspirin for primary prevention, discontinuing aspirin was associated with a 28% higher rate of CV events than continuing on aspirin, an absolute risk increase of 6.9 per 1000 PY at risk, or an additional CV event per year in 1 of every 146 patients who discontinued aspirin.
- Patients who stopped taking aspirin after a period of 4 timely dispenses had an early risk increase for CV events compared with those who collected their fifth dispense on time. The median time to the first CV event in those who did not collect their fifth dispense on time was one-third the time of those who collected their dispense on schedule (time ratio: 0.31; 95% CI: 0.22–0.43).
The discontinuation of low-dose long-term aspirin use for CVD prevention in the absence of major surgery or bleeding, was associated with a >30% increased CV risk, shortly after discontinuation. These findings support the use of aspirin in CVD prevention, and justifies further measures to ensure treatment persistence in this setting.