Context: Rheumatoid arthritis (RA) and psoriasis have been linked with insulin resistance and diabetes mellitus (DM). Prior investigations suggest that systemic immunosuppressive drugs may improve insulin resistance and reduce the risk of DM.
Objective: To compare the risk of newly recorded DM among participants diagnosed with RA or psoriasis based on use of a variety of disease-modifying antirheumatic drugs (DMARDs).
Design, setting, and participants: A retrospective cohort study among 121,280 patients with a diagnosis of either RA or psoriasis on at least 2 visits. The analyses were conducted in the context of 2 large health insurance programs, 1 in Canada and 1 in the United States, using administrative data. The mean follow-up was 5.8 months and began with the first prescription for a DMARD after study eligibility was met. Drug regimens were categorized into 4 mutually exclusive groups: (1) tumor necrosis factor (TNF) inhibitors with or without other DMARDs; (2) methotrexate without TNF inhibitors or hydroxychloroquine; (3) hydroxychloroquine without TNF inhibitors or methotrexate; or (4) other nonbiologic DMARDs without TNF inhibitors, methotrexate, or hydroxychloroquine (reference exposure).
Main outcome measure: Newly recorded DM as evidenced by a new diagnosis of DM with use of a DM-specific medication.
Results: The study cohort consisted of 13,905 participants with 22,493 treatment episodes starting 1 of the categories of DMARD regimens between January 1996 and June 2008. New diabetes cases and respective incidence rates per 1000 person-years were: other nonbiologic DMARDs (55 cases among 3993 treatment episodes; rate, 50.2; 95% confidence interval [CI], 47.3-53.2); TNF inhibitors (80 cases among 4623 treatment episodes; rate, 19.7; 95% CI, 19.1-20.3); methotrexate (82 cases among 8195 treatment episodes; rate, 23.8; 95% CI, 23.0-24.6); and hydroxychloroquine (50 cases among 5682 treatment episodes; rate, 22.2; 95% CI, 21.3-23.1). The multivariate adjusted hazard ratios for DM were 0.62 (95% CI, 0.42-0.91) for TNF inhibitors, 0.77 (95% CI, 0.53-1.13) for methotrexate, and 0.54 (95% CI, 0.36-0.80) for hydroxychloroquine compared with other nonbiologic DMARDS.
Conclusion: Among patients with RA or psoriasis, the adjusted risk of DM was lower for individuals starting a TNF inhibitor or hydroxychloroquine compared with initiation of other nonbiologic DMARDs.