Metformin-inclusive therapy reduces the risk of stroke in patients with diabetes: a 4-year follow-up study.

Metformin is a kind of oral hypoglycemic agents commonly prescribed to patients with diabetes mellitus. Although past studies had proven its protective effect on cardiovascular risk and related mortality, the evidence of metformin on stroke prevention was still insufficient and conflicting. Our study randomly selected 14,856 patients with diabetes from the database provided by the Taiwan National Health Research Institute, and 2 cohorts were formulated according to whether metformin was in the prescription record. All cases were followed up for 4 years to track their stroke incidence. As a result, 701 (17.5%) of 3999 diabetic patients had stroke without metformin use, whereas 994 (9.2%) of 10,857 patients had stroke with metformin use. Cox proportional hazard regressions showed that the stroke hazard ratio (HR) of metformin was .383. After adjustment for the patients' age, gender, hypertension, atrial fibrillation, hyperlipidemia, coronary artery disease, and medications including antiplatelets, coumadin, statin, and estrogen use, the HR was still .468. Further stratified analysis revealed that metformin had more protective effect in the patients with higher risk of stroke. Therefore, metformin should be placed in priority when prescribing oral hypoglycemic agents for diabetic patients when considering stroke prevention according to our study.