A meta-analysis used 10 studies (not including the study described in the previous article) of patients with type 2 diabetes to compare the effects of metabolic surgery and medical treatment on outcomes including new microvascular complications, nephropathy, neuropathy, and remission of pre-existing nephropathy. The data came from three randomized controlled trials (RCTs), three retrospective clinical controlled trials (CCTs), three case-control studies, and one prospective CCT, with follow-up ranging from one to 15 years.
The study was published in the February British Journal of Surgery. The following commentary by Reema Shah, MD, was published in the ACP Journal Club section of the July 17 Annals of Internal Medicine.
Several large RCTs in patients with diabetes have shown that intensive glucose lowering consistently reduces risk for microvascular diabetes outcomes, including retinopathy, nephropathy, and neuropathy. Metabolic surgery is emerging as another effective way to lower glucose in type 2 diabetes, leading to partial or complete remission in up to 73% of patients. However, does it also reduce long-term diabetes outcomes?
The well-done systematic review and meta-analysis of observational studies and RCTs by Billeter and colleagues compared metabolic surgery with medical therapy for microvascular outcomes in patients with type 2 diabetes. It found that metabolic surgery reduced the risk for nephropathy and retinopathy (but not neuropathy) and improved preexisting nephropathy in the overall meta-analysis. However, these results were largely driven by observational studies, and analysis of RCTs alone showed no evidence of benefit for most outcomes. The discrepancy may be explained by either the confounding inherent to observational studies (which might bias the findings towards benefit) or insufficient power in the RCTs (which might have missed a true benefit). Whatever the explanation, the results are promising and add to the body of literature showing benefits of metabolic surgery in management of type 2 diabetes. They also highlight the need for further RCTs assessing the effect of metabolic surgery on microvascular diabetes outcomes.