The FDA arrived at this decision based on results from two large statin studies and a review of other data. In Justification for the Use of Statins in Primary Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER) study the risk of diabetes was 27% higher in patients that received rosuvastatin (Crestor) than placebo-treated patients. In the JUPITER study 3% of patients that received rosuvastatin compared to 2.4% of patients that received placebo developed diabetes.
In Pravastatin or Atorvastatin Evaluation and Infection Therapy – Thrombolysis In Myocardial Infarction 22 (PROVE-IT TIMI 22) sub-study high-dose atorvastatin (Lipitor) was associated with increased blood glucose. Analysis of other published studies also showed that statins increase HbA1c and/or fasting blood glucose, and the risk of being diagnosed with diabetes regardless of the dose or statin used in the studies.
Based on the available evidence the FDA concluded that the public should be aware of this risk. The FDA also pointed out that the risk is small and the new information should not scare people.
Interestingly, the change in prescribing information does not include pravastatin (Pravachol) because of the West of Scotland Coronary Prevention Study (WOSCOPS) where the incidence of diabetes was reduced by 30% in pravastatin-treated patients compared to patients who did not receive pravastatin.