Abstract
OBJECTIVE: To examine the risk of diabetes mellitus (DM) among subjects with rheumatoid arthritis (RA), psoriatic arthritis or psoriasis (PsA/PsO), compared with non-rheumatic controls. METHODS: Study cohorts were assembled using linked healthcare utilisation data from British Columbia. All people with at least two diagnoses of RA or PsA/PsO were included and compared with a cohort of people without any known rheumatic disease. The outcome of interest was a diagnosis of new-onset DM, as defined by initiation of an antidiabetic drug. Incidence rates (IRs) per 1000 person-years and IR ratios were calculated and Cox regression models were constructed to determine the hazard ratio (HR) for diabetes by age, gender, systemic immunosuppressive drug and glucocorticoid use. RESULTS: The study cohort comprised 48 718 subjects with RA, 40 346 with PsA/PsO and 442 033 without any rheumatic disease. The IR for DM among subjects with RA was 8.6 per 1000 person-years (95% CI 8.5 to 8.7), PsA/PsO 8.2 (95% CI 8.1 to 8.3) and for non-rheumatic controls 5.8 (95% CI 5.8 to 5.8). The adjusted HR for RA compared with non-rheumatic controls was 1.5 (95% CI 1.4 to 1.5) and 1.4 (95% CI 1.3 to 1.5) for PsA/PsO. CONCLUSIONS: RA and PsA/PsO appear to be associated with an increased risk of DM. The ability of potent antirheumatic treatments to reverse this trend warrants study.