Antimalarial Adherence and Risk of Cardiovascular Events in Patients With Rheumatoid Arthritis and Systemic Lupus Erythematosus: A Population‐Based Study

Abstract

ObjectiveTo assess the association between antimalarial adherence and cardiovascular events among incident rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) population‐based cohorts.MethodsAll patients with incident RA/SLE and incident antimalarial use in British Columbia, Canada, between 01/1997 and 03/2015 were identified using provincial administrative databases. The outcomes were incident cardiovascular events, including myocardial infarction (MI), stroke, or venous thromboembolism (VTE). The exposure was antimalarial adherence with levels: discontinuation (proportion of days covered (PDC=0), non‐adherence (0<PDC<0.90), and adherence (PDC≥0.90). We used marginal structural models (MSM) to estimate the effect of antimalarial adherence on the rate of cardiovascular events, accounting for potential confounders.ResultsWe identified 16,538 individuals with incident RA/SLE and incident antimalarial use, without any cardiovascular event prior to index date. Over 9 years mean follow‐up, 2,174(13.2%) incident cardiovascular events were observed. The adjusted hazard ratios (aHRs) for incident cardiovascular event for antimalarial adherence relative to discontinuation was 0.72(95% CI: 0.64‐0.81), and for non‐adherence was 1.01(95% CI: 0.90‐1.14). Additionally, the aHR for all cardiovascular events, MI, stroke and VTE for adherence relative to non‐adherence was 0.71(95% CI: 0.61‐0.82), 0.62(95% CI: 0.51‐0.75), 0.45(95% CI: 0.36‐0.58), and 0.65(95% CI: 0.46‐0.93), respectively. We found older age modified the association between antimalarial adherence and cardiovascular events (p=0.02).ConclusionWhen people newly diagnosed with RA or SLE take their antimalarial regularly as prescribed (PDC≥0.90), they have 29% lower risk of sustaining a cardiovascular event than patients with a lower degree of adherence (PDC<0.90) and a 28% lower risk than if they discontinue antimalarials.image