In a study that included nearly 14,000 patients with rheumatoid arthritis or psoriasis, the use of certain disease-modifying antirheumatic drugs was found to lower the risk of diabetes, according to a study in the June 22/29 issue of JAMA.

Two common systemic inflammatory conditions, rheumatoid arthritis (RA) and psoriasis, predispose patients to insulin resistance and may place patients at risk for diabetes mellitus (DM). The treatment of psoriasis and RA includes disease-modifying antirheumatic drugs (DMARDs) such as tumor necrosis factor (TNF) inhibitors, which are directed against the inflammatory response, according to background information in the article. The relationship between these conditions and DM suggests that systemic immunosuppression may also reduce the risk for DM.

Daniel H. Solomon, M.D., M.P.H., of Brigham and Women's Hospital, Boston, and colleagues examined the relationship between DMARD medications and the risk of newly diagnosed DM among participants with RA or psoriasis. The researchers conducted 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 average 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) 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.

The final study cohort consisted of 13,905 participants with 22,493 new treatment episodes starting 1 of the categories of DMARD regimens between January 1996 and June 2008. The researchers found 267 newly diagnosed cases of DM: 55 cases among 3,993 treatment episodes with nonbiologic DMARD users; 80 cases among 4,623 treatment episodes with TNF inhibitor users; 82 cases among 8,195 treatment episodes with methotrexate users; and 50 cases among 5,682 treatment episodes with hydroxychloroquine users. The incidence rates for DM were highest for individuals who switched to other nonbiologic DMARDs and lowest for TNF inhibitor users. "The fully adjusted models suggest a reduced relative risk of DM for TNF inhibitor and hydroxychloroquine compared with other nonbiologic DMARDs," the authors write.

According to the authors, "The findings from this epidemiologic study should be considered hypothesis-generating. However, considering these results in light of prior findings regarding improved insulin and glucose metabolism and reduced DM risk with hydroxychloroquine and TNF inhibitors, there is evidence suggesting a possible role for DMARDs and immunosuppression in DM prevention. A randomized controlled trial testing the ability of these agents to prevent DM among participants with systemic inflammatory disorders should be considered."

JAMA. 2011;305[24]2525-2531.