Editor's Impact Statement
Comment on Today's Focus On Diabetes by Vivian Fonseca MD
-Effects of rosuvastatin and atorvastatin on glycaemic control in Type-2 diabetes-the CORALL study
Clinical Impact, from MDLinx , 05/24/2012

Background

Recently there have been reports of increased risk of developing type 2 diabetes in patients on statin therapy, prompted by such an increase seen in the JUPITER trial (which was done in patients with a high prevalence of obesity and pre –diabetes). However, very little is known as to whether statin therapy (used in a high proportion of patients with diabetes) affect glucose control.

What was done in this study?

The CORALL study was a 24–week, open–label, randomized, parallel–group, multi–centre study, designed to compare the cholesterol–lowering effects of rosuvastatin compared with atorvastatin in patients with Type 2 diabetes. ? This post hoc analysis examined whether high–dose statin therapy in patients with Type?2 diabetes and dyslipidaemia influenced variables of glycaemic control. Fasting plasma glucose levels and HbA(1c) levels were collected at baseline and at 6 and 18 weeks. What were the results?

Treatment with the highest dose of statins, i.e. atorvastatin 80?mg and rosuvastatin 40 mg at 18 weeks from baseline, was associated with a small but statistically significant increase in HbA1c levels; baseline of 7.4 ± 1.0% to 7.7 ±1.3%) for atorvastatin (P =0.003) and from baseline of 7.6 ±1.0% to 7.9 ±1.2% for rosuvastatin (P<0.001). Mean fasting plasma glucose increased from baseline 8.7 ± 2.4 mmol/l to 9.5 ± 3.0 mmol/l upon treatment with atorvastatin 20mg (P=0.002) and 9.0 ± 3.0 mmol/l after treatment with 80 mg (not significant compared with baseline). The mean fasting plasma glucose did not change after treatment with rosuvastatin (9.1 ± 2.7 mmol/l at baseline, 8.9 ± 2.7 mmol/l with 10 mg, 9.4 ± 2.9 mmol/l with 40mg).

What are the limitations and conclusions of the study?

The major limitation of the study is that it is a post hoc analysis that was not pre specified and there is not enough information on compliance with and prescriptions of diabetes medications. Furthermore, the duration of the study was relatively short. In addition, there is a discrepancy between the effect on A1c and fasting glucose. This suggests a possible effect on post prandial glucose regulation, which was unfortunately not carefully assessed.

It is also not clear which type of diabetes therapy would overcome these effects and maintain glycemic control.

The authors conclude that Glycemic control deteriorated in patients with diabetes following high–dose statin therapy.

What are the Implications? Future controlled studies are needed to verify these findings and, if confirmed, determine whether such changes represent a true and long lasting decline in glycemic control, and what can be done to overcome this limitation of effective therapy. Presently, it appears that, based on the overwhelming prospective trial data available, the preventive effect of statin therapy on CV events supersedes that of the slight increase in HbA1c.