Metformin May Help Keep Diabetes at Bay, but No More So Than Intensive Diet and Exercise

By Reuters Staff

December 20, 2019

NEW YORK (Reuters Health) - Metformin may help prevent or delay the onset of type 2 diabetes in high-risk adults, suggest results of a Cochrane review.

Dr. Kasper Madsen of the University of Copenhagen and colleagues reviewed 20 randomized trials with 6,774 total patients. The trials compared metformin to any pharmacological glucose-lowering intervention, behavior-changing intervention, placebo, or standard care in patients with impaired glucose tolerance or fasting glucose, moderately elevated glycosylated hemoglobin A1c (HbA1c), or a combination of these conditions.

The intervention period varied from one to five years; none was judged to be at low risk of bias.

Fifteen studies compared metformin against a diet-and-exercise intervention, eight compared metformin against intensive diet and exercise and three compared metformin plus intensive diet and exercise against intensive diet and exercise only.

When compared with placebo or standard diet and exercise, metformin significantly reduced or delayed onset of diabetes in those at risk based on moderate-quality evidence (relative risk, 0.50; P<0.001), the researchers found.

However, when compared with an intensive diet-and-exercise program, metformin did not provide any added benefit in reducing or delaying development of diabetes (moderate-quality evidence), they report.

Combining metformin with intensive diet and exercise (compared to intensive diet and exercise alone) showed neither an advantage nor disadvantage regarding the development of diabetes (very low‐quality evidence).

Seven studies compared metformin with another glucose-lowering agent. "There was neither an advantage or disadvantage when comparing metformin with acarbose (three studies) or a thiazolidinedione (three studies) with respect to the development of diabetes," the authors note.

One study compared metformin with a sulphonylurea but the trial did not report patient-important outcomes.

In general, the reporting of serious side effects was sparse, the researchers found. "Few participants died and we did not detect a clear difference between the intervention and comparator groups. We also did not detect an advantage or disadvantage of metformin in relation to health-related quality of life," they say.

"Data were sparse or unavailable on mortality, macrovascular and microvascular diabetic complications, and health‐related quality of life," the team adds. "All of the included studies had problems in the way they were conducted or reported."

"Future studies should investigate more patient-important outcomes such as complications of diabetes and especially the side effects of the drugs," the authors say.

They identified 11 ongoing trials that might provide more data on the topic. "These trials will add a total of 17,853 participants in future updates of this review," they note.

SOURCE: Cochrane Database of Systematic Reviews, online December 3, 2019.