A meta-analysis published in the BMJ and reported on in Medscape highlights the following findings which I have very briefly summarised below:
- Hba1c lower by 0.5%
- Weight lower by 1 Kg
- Insulin reduction by 5 units
- No difference in all cause mortality
“Of 26 randomized trials identified, enrolling a total of 2286 participants, 23 trials enrolling a total of 2117 participants had usable data. Risk of bias was high for all trials, and there were few data for patient-relevant outcomes.
Compared with insulin alone, metformin and insulin were not associated with any significant difference in all-cause mortality (relative risk [RR], 1.30; 95% confidence interval [CI], 0.57 – 2.99) or cardiovascular mortality (RR, 1.70; 95% CI, 0.35 – 8.30). Trial sequential analyses revealed that additional trials were needed to allow reliable conclusions concerning these outcomes.
Severe hypoglycemia occurred significantly more frequently with metformin and insulin than with insulin alone, according to a fixed-effect model but not a random-effects model (RR, 2.83; 95% CI, 1.17 – 6.86). Compared with insulin alone, metformin and insulin were associated with reduced hemoglobin A1c, weight gain, and insulin dose in a random-effects model. Trial sequential analyses showed sufficient evidence for lowering of hemoglobin A1c by 0.5 percentage point, weight gain by 1 kg, and insulin dose by 5 U/day.
“There was no evidence or even a trend towards improved all-cause mortality or cardiovascular mortality with metformin and insulin, compared with insulin alone in type 2 diabetes,” the study authors write. “Data were limited by the severe lack of data reported by trials for patient relevant outcomes and by poor bias control.””