CONTEXT:

Hydroxychloroquine, a commonly used antirheumatic medication, has hypoglycemic effects and may reduce the risk of diabetes mellitus.

OBJECTIVE:

To determine the association between hydroxychloroquine use and the incidence of self-reported diabetes in a cohort of patients with rheumatoid arthritis.

DESIGN, SETTING, AND PATIENTS:

A prospective, multicenter observational study of 4905 adults with rheumatoid arthritis (1808 had taken hydroxychloroquine and 3097 had never taken hydroxychloroquine) and no diagnosis or treatment for diabetes in outpatient university-based and community-based rheumatology practices with 21.5 years of follow-up (January 1983 through July 2004).

MAIN OUTCOME MEASURES:

Diabetes by self-report of diagnosis or hypoglycemic medication use.

RESULTS:

During the observation period, incident diabetes was reported by 54 patients who had taken hydroxychloroquine and by 171 patients who had never taken hydroxychloroquine, with incidence rates of 5.2 per 1000 patient-years of observation compared with 8.9 per 1000 patient-years of observation, respectively (P < .001). In time-varying multivariable analysis with adjustments for possible confounding factors, the hazard ratio for incident diabetes among patients who had taken hydroxychloroquine was 0.62 (95% confidence interval, 0.42-0.92) compared with those who had not taken hydroxychloroquine. In Poisson regression, the risk of incident diabetes was significantly reduced with increased duration of hydroxychloroquine use (P < .001 for trend); among those taking hydroxychloroquine for more than 4 years (n = 384), the adjusted relative risk of developing diabetes was 0.23 (95% confidence interval, 0.11-0.50; P < .001), compared with those who had not taken hydroxychloroquine.

CONCLUSION:

Among patients with rheumatoid arthritis, use of hydroxychloroquine is associated with a reduced risk of diabetes.