Roni Rabin at the New York Times suggests an answer:
“The Food and Drug Administration updated its advisory about statins in 2012 to include warnings about the slightly increased risk of higher blood sugars and Type 2 diabetes, based in part on two large analyses of earlier studies that controlled for diabetes risk factors like being overweight or being older. One found a 9 percent increase in the risk of diabetes among statin users, and the other a 12 percent increase, with a greater risk for those on intensive rather than moderate doses of the drugs.
The 2012 F.D.A. advisory also warns of other side effects of statins, such as muscle injury, rare cases of liver damage and reports of memory loss and confusion.”
Paleo Diabetic 