Abstract 1329: Discontinuation of Low-dose Acetylsalicylic Acid Treatment for Secondary Prevention of Cardiovascular Outcomes
Objectives: To assess what proportion of patients treated with low-dose acetylsalicylic acid (ASA) for secondary prevention of cardiovascular events discontinue this treatment, and to identify risk factors for discontinuation.
Methods: The Health Improvement Network (THIN) UK primary care database was used to identify individuals aged 50 – 84 years with at least 2 prescriptions of low-dose ASA (75–300 mg/day) in 2000 –2007 (n=35 639). The study cohort was followed from the first day after the initial prescription until the earliest occurrence of one of the following: discontinuation of low-dose ASA (a period of ≥30 days after the last prescription would have been used up [assuming full compliance], with no refill of the prescription during this time); death; diagnosis of an alcohol-related condition or cancer; or the end of the study period. The mean follow-up time was 2.1 years.
Results: Almost 50% of patients discontinued low-dose ASA treatment (n=15 926; incidence: 21.2 per 100 person-years; 95% confidence interval [CI]: 20.9 –21.5). The mean time to discontinuation was 11.4 months (range: 1.1–93.7) over the whole follow up period, and 4.7 months (range: 1.1–12.0) in the first year. The incidence of discontinuation was higher in the first year (42.7 per 100 person-years; 95% CI: 41.9 – 43.5) than the rest of the study period (9.4 per 100 person-years; 95% CI: 9.1–9.7). Compared with patients aged 75– 84 years, those aged 50 – 64 years were more likely to discontinue low-dose ASA treatment (hazard ratio [HR]: 1.2; 95% CI: 1.2–1.3). There was no significant difference in discontinuation rates between men and women. Discontinuation was slightly more common in current smokers than non-smokers (HR: 1.1; 95% CI: 1.0 –1.1). There was no association between discontinuation and socioeconomic status or healthcare utilization. The risk of discontinuation was 36 –53% higher in patients with an initial indication of unstable angina, ischemic heart disease or cerebrovascular disease than those with an initial indication of myocardial infarction (MI).
Conclusions: Discontinuation of low-dose ASA treatment is common, especially in the first year of treatment. Younger patients and those with an initial indication other than MI are especially likely to discontinue treatment.