Does statin therapy increase the chance of type 2 diabetes mellitus?

A paper in the Journal of the American College of Cardiology by Waters DD et al [1] evaluated the results from three large randomized clinical trials to find out the predictors of new onset diabetes in patients treated with atorvastatin. They used a standard definition of diabetes mellitus and excluded those who were diabetic at baseline evaluation. One trial with about three thousand eight hundred patients randomized to 80 mg of atorvastatin had 351 new onset type 2 diabetes while those randomized to 10 mg of atorvastatin had 308 new onset type 2 diabetes (p = 0.226). In another trial in which over 3700 patients were randomized to 80 mg atorvastatin had 239 new onset diabetes while there was 208 new onset diabetes in a similar group randomised to 20 mg simvastatin (p = 0.072). In a third trial comparing 80 mg atorvastatin with placebo, there were 166 new onset type 2 diabetes in the atorvastatin group and 115 in the placebo group (p = 0.011). There were about 1900 patients in either group.

It is noteworthy that in all these three trials, baseline fasting blood glucose, body mass index, hypertension and fasting triglycerides where independent predictors of new onset type 2 diabetes mellitus. The cardiovascular event rates in those with new onset type 2 diabetes mellitus was 11.3% while it was 10.8% in those without (p = 0.69), taking all the three trials together. The authors concluded that there is a slightly increased risk of new onset type 2 diabetes mellitus and features of metabolic syndrome are predictive of new onset type 2 diabetes mellitus.
Well designed trials to specifically address this issue are definitely needed before we can make any specific conclusions as post hoc analyses have their own limitations.

Reference

1. Waters DD, Ho JE, DeMicco DA, Breazna A, Arsenault BJ, Wun CC, Kastelein JJ, Colhoun H, Barter P. Predictors of new-onset diabetes in patients treated with atorvastatin: results from 3 large randomized clinical trials. J Am Coll Cardiol, 2011; 57:1535-1545.