Metformin Lowers Risk of Heart Disease and Mortality

Not only is metformin the oldest diabetes drug, it is also still the first choice for diabetes treatment. Dr. Nils Ekström of the University of Gothenburg in Sweden, and colleagues set out to study the safety and effectiveness of metformin in a large group of men and women with type 2 diabetes.

They found that type 2 diabetes patients taking metformin may have a lower risk of heart disease and death, compared to patients on insulin.

These findings suggest that metformin has a lower risk of side effects than other common diabetes drugs. The study included more than 51,000 patients with type 2 diabetes.

Patients taking metformin also had a slightly lower risk of death compared to patients taking oral hypoglycemic agents.

Metformin was first created and found to lower blood sugar levels in the 1920s and approved for use in the U.S. in 1950. Almost a century later, it is still a first-line treatment for type 2 diabetes.

On top of finding that patients taking metformin had a lower risk of heart disease and death, the researchers found that patients with weakened kidney function did not have an increased risk of heart disease, death or serious infection.

Other findings showed that metformin, compared to any other treatment, was associated with a lower risk of acidosis (too much acid in the body fluids) and serious infection among patients with an estimated Glomerular Filtration Rate, or eGFR (a measure of kidney function), of 45 to 60.

Among patients with an eGFR of 30 to 45, metformin had no increased risk of all-cause mortality, acidosis, serious infection or heart disease.

An eGFR of 60 and above is considered normal. Kidney disease is marked by an eGFR below 60. Kidney failure is marked by an eGFR of 15 or below.

Metformin was also associated with a lower all-cause mortality (risk of death from all causes).

• patients taking oral hypoglycemic agents had a hazard ratio of 1.02 for heart disease
• patients taking oral hypoglycemic agents had a hazard ratio of 1.13 for all-cause mortality
• patients taking insulin had a hazard ratio of 1.18 for heart disease
• patients taking insulin had a hazard ratio of 1.34 for all-cause mortality

(A hazard ratio is a measure of how often one event happens in one group versus how often it happens in another group over a period of time. A hazard ratio of more than one means that the particular event happens more in one group than the other.)

"In clinical practice, the benefits of metformin use clearly outbalance the risk of severe side effects," the authors said.

BMJ, July 13, 2012.