The researchers found statin therapy was associated with a 46% increased risk of type 2 diabetes, even after adjustment for confounding factors.
The link between statin use and higher risk of diabetes is not new. Back in 2013, for example, Medical News Today reported on a study published in The BMJ that found certain statins - particularly atorvastatin (Lipitor), rosuvastatin (Crestor) and simvastatin (Zocor) - raised the risk of diabetes by up to 22%.
But according to the researchers of this latest study - including Prof. Markku Laakso of the Institute of Clinical Medicine at the University of Eastern Finland and Kuopio University Hospital in Finland - such studies have had numerous limitations.
The team explains that many of these studies have included selective populations, such as those at high risk of cardiovascular disease. As a result, findings may not be applicable to the general population.
The researchers also note that these studies have often included participants whose diabetes has been self-reported or based on their fasting glucose measurements, which may underestimate the actual number of incident diabetes cases.
Increased risk 'most likely linked to statins that reduce insulin sensitivity and secretion'
For their study, Prof. Laakso and colleagues analyzed the effects of statin use on 8,749 nondiabetic Caucasian men aged 45-73 years who were part of the Finland-based Metabolic Syndrome in Men (METSIM) study.
During the 5.9-year follow-up, 625 men were diagnosed with type 2 diabetes, as determined by either an oral glucose tolerance test (OGTT), an HbA1c level of at least 6.5%, or the commencement of antidiabetic medication.
The results of the analysis revealed that men who were treated with statins were at 46% higher risk of diabetes than men who were not treated with statins.
This 46% increased diabetes risk was present even after adjusting for the men's age, body mass index (BMI), waist circumference, physical activity levels, smoking status, alcohol intake, family history of diabetes and treatment with beta-blockers and diuretic medications.
The researchers also assessed changes in insulin resistance and insulin secretion among men who were treated with statins. They found that statins led to a 24% reduction in insulin sensitivity during follow-up, as well as a 12% reduction in insulin secretion.
For two statins - simvastatin and atorvastatin - the researchers found the associated risk of type 2 diabetes was dose-dependent, as were the reductions in insulin sensitivity and insulin secretion among the men taking these statins.
After accounting for the aforementioned confounding factors, the team found high-dose simvastatin was linked to a 44% higher risk of type 2 diabetes, while a lower dose was linked to a 28% increased risk. High-dose atorvastatin was associated with a 37% increased risk of type 2 diabetes.
Of the study participants, 53% were taking atorvastatin and 29% were taking simvastatin.
Based on their results, the researchers say:
"Statin therapy was associated with a 46% increased risk of type 2 diabetes after adjustment for confounding factors, suggesting a higher risk of diabetes in the general population than previously reported.
The association of statin use with increased risk of developing diabetes is most likely directly related to statins decreasing both insulin sensitivity and secretion."
Prof. Laakso and colleagues say that while one strength of this study is its large size, the fact that all participants were male and Caucasian means the findings may not be generalizable to women or those of other ethnicities.
In February, Medical News Today reported on a study claiming - contrary to previous findings - statins may not protect against Parkinson's disease.