Differing effect of statins on insulin sensitivity in non-diabetics: a systematic review and meta-analysis

Background: To determine whether individual statins had differing effects on insulin sensitivity (IS) in patients without pre-existing diabetes mellitus.

Methods: A systematic literature search of MEDLINE, EMBASE and Cochrane CENTRAL was conducted through December 2008. Trials were included if they compared pravastatin, atorvastatin, rosuvastatin or simvastatin to placebo/control, excluded patients with diabetes, and reported data on insulin sensitivity/resistance. IS data was pooled and evaluated as standardized mean differences (SMDs) and 95% confidence interval (CI) using a random-effects model.

Results: 16 studies (n=1146) were included, with patients receiving pravastatin in three trials (n=164), atorvastatin in five trials (n=315), rosuvastatin in five trials (n=419), and simvastatin in five trials (n=369). When pooled as a class, statins had no significant impact on IS as compared with placebo/control [SMD -0.084 (95% CI -0.210 to 0.042); p=0.19]. Pravastatin was found to significantly improved IS [SMD 0.342 (95% CI 0.032-0.621); p=0.03], whereas simvastatin significantly worsened IS [SMD -0.321 (95% CI -0.526 to -0.117); p=0.03].

Conclusions: Statins do not appear to demonstrate a 'class effect' on IS in patients without diabetes. Differences between individual statins likely exist that may partially explain the findings of previously conducted meta-analyses examining the impact of statins on the development of diabetes.