Abstract 11045: Longer Duration of Diabetes Diminishes Aspirin's Effect on Primary Prevention of Cardiovascular Events: Results from the JPAD2 Study

Abstract

Efficacy of low-dose aspirin on primary prevention of cardiovascular events remains controversial in diabetes, although it was proven in general population in previous clinical trials. We conducted the JPAD trial to evaluate whether low-dose aspirin could prevent cardiovascular events in patients with type 2 diabetes and no history of cardiovascular disease. 2,536 patients were randomly assigned to aspirin (81 or 100 mg daily) or no aspirin groups, and followed for a median of 4.4 years. We reported aspirin was more effective in patients with shorter duration of diabetes (AHA Scientific Sessions 2011). Thus we hypothesized longer duration of diabetes diminishes aspirin’s effect. Now, we followed the cohort of JPAD trial until July 2011 as an observational study (named JPAD2 study), and inspected our hypothesis. Aspirin administration depended on each physician’s decision. The analysis included 2,297 patients whose onset of diabetes was reported. The median follow-up period became 7.1 years. Over 80% of patients preserved original allocation of aspirin. First, we stratified patients according to quartile duration of diabetes at baseline of the original JPAD trial, and assessed aspirin’s effect on preventing cardiovascular events. The hazard ratio of cardiovascular events by aspirin was 1.27, 1.14, 1.11, and 0.54 for patients with baseline diabetic duration of ≥12.3, 7.0 to 12.3, 2.9 to 7.0, and <2.9 years, respectively. Aspirin reduced cardiovascular events only in the shortest quartile of diabetic duration, but statistical significance was not observed. Next, we compared aspirin’s effect between the original JPAD and JPAD2 cohorts. Longer duration of diabetes gradually decreased aspirin’s effect in both cohorts; however, the plots of the JPAD2 cohort shifted to ‘favor control’ in all points compared with the original JPAD cohort (Figure). These results suggest that longer duration of diabetes diminishes aspirin’s effect on preventing cardiovascular events.