The finding comes from a prospective study of 4,905 adults with RA and no initial diagnosis of diabetes. Hydroxychloroquine had been taken by 1,808 patients.
Over 21 years of follow-up, 54 patients who had taken hydroxychloroquine and 171 who had never taken it reported incident diagnoses of diabetes.
Analysis showed patients who had taken hydroxychloroquine had a 38 per cent reduced risk of developing diabetes, compared with those who had never taken the drug. This risk was reduced to 77 per cent, if patients had taken hydroxychloroquine for more than four years.
The effect of duration of hydroxychloroquine use suggests this drug has a biological effect on glucose metabolism, say the researchers.
JAMA 2007; 298: 187-93