Despite high expectations that metformin would reduce cardiovascular risk in people without type 2 diabetes, few benefits have been found in a randomized trial of 173 patients with established cardiovascular disease already taking statins (Preiss D et al. Lancet Diabetes & Endocrinology, doi:10.1016/S2213-858770152-9 [published online November 7, 2013]).
Previous research found that metformin led to a 39% reduction in risk of myocardial infarction over 10 years in overweight diabetic patients. Whether metformin offered similar benefits for people without diabetes had not been tested until the Carotid Atherosclerosis: Metformin for Insulin Resistance (CAMERA) trial, which randomized patients to receive metformin or placebo for 18 months.
Slomski A. Metformin Has Little Cardiovascular Effect on People Without Diabetes. JAMA. 2013;310(24):2605. doi:10.1001/jama.2013.284786