COMMENTARY

Should Everyone Take Metformin?

Gregory A. Nichols, PhD

Disclosures

December 04, 2014

In This Article

Can People With Type 2 Diabetes Live Longer Than Those Without? A Comparison of Mortality in People Initiated With Metformin or Sulphonylurea Monotherapy and Matched Non-diabetic Controls

Bannister CA, Holden SE, Jenkins-Jones S, et al
Diabetes Obes Metab. 2014;16:1165-1173

Does Metformin Reduce Mortality?

In this retrospective observational study, researchers used data from the United Kingdom's Clinical Practice Research Datalink to identify patients with diabetes who initiated metformin or SU monotherapy between 2000 and 2012 and continued treatment for at least 180 days. These persons were matched to nondiabetic individuals on age, sex, history of cancer, and smoking status. All were then followed for up to 5.5 years to compare subsequent mortality.

Patients initiating metformin therapy were compared with those initiating treatment with an SU, and both diabetic groups were also compared with their matched nondiabetic controls. Multivariable models comparing survival time included covariates for age; sex; Charlson comorbidity index; smoking status; and previous antihypertensive, lipid-lowering, and antiplatelet therapy.

Metformin: Better Survival Than People Without Diabetes

The study included 78,241 patients with diabetes who initiated metformin therapy, 12,222 patients who initiated SU therapy, and an identical number of matched nondiabetic controls. Metformin initiators were significantly younger and more obese than SU initiators (body mass index, 32.4 vs 27.1 kg/m2). A1c at initiation was high for both groups, but significantly higher among the SU group (9.2% vs 8.6%).

Crude death rates were substantially lower for metformin users than SU users (14.4 vs 50.9 per 1000 person-years). After multivariable adjustment, survival time was 38% lower among SU users. All subgroup comparisons favored metformin over SU and were statistically significant.

Perhaps the most striking finding was that survival time for controls was 15% shorter than for matched metformin users. This finding was consistent across all subgroups, nearly all of which demonstrated statistical significance, and was particularly strong among patients with high comorbidity. Furthermore, the overall result was not affected after adjustment for use of cardiovascular prophylactic medication during follow-up.

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