Study: Metformin with insulin associated with a higher risk of all-cause death

CHICAGO — A study published Wednesday on JAMA's website found that diabetes patients taking metformin had a higher risk of all-cause death when insulin was added to their treatment as compared to when sulfonylureas were added to treatment.

"Among patients with diabetes who are receiving metformin, the addition of insulin compared with sulfonylurea was associated with an increased risk of a composite of nonfatal cardiovascular outcomes and all-cause mortality," wrote Christianne Roumie of the Nashville VA Medical Center. "These findings require further investigation to understand risks associated with insulin use in these patients and call into question recommendations that insulin is equivalent to sulfonylureas for patients who may be able to receive an oral agent."

According to the study, there was a moderately higher rate of death associated with patients who were treated with insulin and metformin. There was no statistical difference in the rate of cardiovascular death in those patients who had added insulin to their metformin regimen vs. those who had added sulfonylurea. 

Roumie concluded that there was no advantage to receiving insulin compared to a sulfonylurea medication, and that there was some risk in treating with the combination of metformin plus insulin.