To evaluate the association between adherence to antimalarials and type 2 diabetes mellitus (DM) in patients with systemic lupus erythematosus (SLE).
Using administrative health databases in British Columbia, Canada, we conducted a retrospective, longitudinal cohort study of patients with incident SLE and incident antimalarial use. We established antimalarial drug courses by defining a new course when a 90-day gap is exceeded between refills and we calculated proportion of days covered (PDC) for each course. We categorized medication taking as: 1) adherent (PDC ≥0.90), 2) nonadherent (0 < PDC < 0.90), and 3) discontinuer (no drug). Type 2 DM outcomes were based on outpatient or inpatient visits, or antidiabetic medication use. We used multivariable Cox proportional hazards models with time-dependent variables.
Over a median of 4.62 years of follow-up in our incident cohort of 1,498 patients with SLE (90.8% women), we recorded 140 incident cases of type 2 DM. Multivariable hazard ratios were 0.61 (95% confidence interval [95% CI] 0.40-0.93) for adherent and 0.78 (95% CI 0.50-1.22) for nonadherent, respectively, as compared to discontinuers.
Our findings of a protective effect of adherence to antimalarials in preventing type 2 DM provides further support for the importance of adherence to antimalarials to obtain the benefits of therapy.