Bariatric Surgery Improves Type 2 Diabetes, Study Finds

Marlene Busko

March 05, 2020

Patients with severe obesity and diabetes who are contemplating bariatric surgery now have data to make a better-informed decision, researchers report.

A large, multicenter US study of such patients has identified similarities and differences in 5-year diabetes remission, diabetes relapse, and glycemic control after the two most common types of bariatric surgery.

In close to 10,000 severely obese patients, rates of having some diabetes remission during the 5 years after surgery were similar and high for both Roux-en-Y gastric bypass (86%) and sleeve gastrectomy (84%).  

Overall, however, patients who had a gastric bypass as opposed to sleeve gastrectomy had lower rates of diabetes relapse, better glycemic control, and greater weight loss.

Importantly, patients and clinicians both provided input into the design of the study by the National Patient-Centered Clinical Research Network (PCORnet), and the study provides real-world data on diabetes outcomes after these two bariatric procedures, lead author Kathleen M. McTigue, MD, from the University of Pittsburgh, Pennsylvania, told Medscape Medical News.

"This study is really most relevant for patients who are struggling with severe obesity and diabetes at the same time," she continued. "What they should know is that bariatric surgery can often make a big difference in terms of their diabetes," For most of these patients, diabetes will go away, "and that might be temporary but it's a really good thing."

The study, published online March 4 in JAMA Surgery, also identified that patients who have more complex type 2 diabetes medication regimens, are older, or are using insulin would likely have a greater improvement in diabetes remission after gastric bypass.  

And "for folks who are not in that situation," McTigue added, "bypass and sleeve might have a similar impact on their diabetes over about 5 years of follow-up."

"I hope that these data will help patients and clinicians realize that bariatric surgery may have a substantial impact on diabetes," McTigue said, keeping in mind that bariatric surgery and a particular procedure may not be not right for everyone, and this is something that patients should discuss with their healthcare providers.

Earlier Conflicting Findings

Smaller studies comparing diabetes remission in obese patients after Roux-en-Y gastric bypass versus sleeve gastrectomy have reported conflicting results, the authors write.

However, it is now especially important to clarify potential improvements in diabetes following these surgeries, given that sleeve gastrectomy is beginning to overtake gastric bypass as the most common bariatric surgery procedure.

Researchers analyzed data from 9710 adults with type 2 diabetes who had gastric bypass or sleeve gastrectomy at 34 PCORnet-affiliated centers in diverse parts of the United States from January 1, 2005 through September 30, 2015.  

Patients all had A1c levels of at least 6.5% or a prescription for a type 2 diabetes medication in the year before surgery, and were all younger than 80 years (mean, 50 years); 73% were women and 72% were white.

In this cohort, 64% of patients had a Roux-en-Y gastric bypass and 36% had a sleeve gastrectomy.

Most surgeries took place between 2010 and 2015, during which time the gastric sleeve procedure became increasingly more common, so by 2014, these two types of surgeries were being performed on roughly equal numbers of patients.

Most patients had a body mass index (BMI) of ≥ 40 kg/m2 (class 3 obesity, sometimes called severe obesity). The remaining 10.6% of patients had a BMI of 35 to 39 kg/m2 (class 2 obesity).

These BMIs are not unexpected, said McTigue, as bariatric surgery is typically considered an appropriate option for people with a BMI > 40 kg/m2 or ≥ 35 kg/m2 with a serious weight-related health problem (eg, type 2 diabetes, hypertension, or severe sleep apnea).  

Patients had a mean A1c of 7.2%, and 25.5% had an A1c < 6.5% (well-controlled diabetes).

The cohort was followed for a median of 2.7 years and out to 5 years.

Diabetes remission — post-surgery A1c < 6.5% after at least 6 months without a prescription for a medication for type 2 diabetes — occurred in 6141 patients, mainly during the first 2 years.

At 5 years, diabetes remission was high after both gastric bypass and gastric sleeve procedures, but it was 10% more likely after gastric bypass (hazard ratio [HR], 1.10).

During this follow-up, diabetes relapse — defined as an A1c ≥ 6.5% and/or a prescription for a type 2 diabetes medication, after remission — was 25% less likely after gastric bypass (HR, 0.75).

Diabetes relapse rates among patients who had a gastric bypass compared with gastric sleeve procedure were 33.1% and 41.6%, respectively.

From baseline to 5 years after surgery, A1c was reduced by 0.45% more after gastric bypass than after gastric sleeve (by 0.8% vs by 0.35%).

And weight loss was more pronounced after gastric bypass than gastric sleeve (24.1% vs 16.1%), a difference of about 10 kg.  

"These findings can help inform patient-centered decision-making," the authors summarize.

Editorialists Urge Expanded Insurance Coverage

"This analysis is an important contribution," because "it included long-term electronic health record data from a large cohort of US patients who had bariatric surgery in a real-world setting," Natalie Liu, MD, and Luke M. Funk, MD, MPH, University of Wisconsin School of Medicine and Public Health, in Madison, write in an invited commentary.  

The most recent data shows there were approximately 250,000 bariatric surgeries performed in the United States in 2018, and about 60% were sleeve gastrectomy and less than 20% were gastric bypass, Funk told Medscape Medical News.

This work builds on previous studies that have shown "bariatric surgery is more efficient than medical management for diabetes remission," he added, and it provides insight into outcomes with the two types of surgeries.

The first take-home message is that "this really is a pretty convincing study of diabetes remission within 5 years."

However, he would also like to see this study continue to determine long-term outcomes at 10, 15, and 20 years.

Second, more insurers and policymakers should consider covering and suggesting bariatric surgery as an option for certain patients with class 1 obesity (BMI 30-34.9 kg/m2).

"The American Diabetes Association recommends consideration of bariatric surgery in patients with diabetes and class 1 obesity or higher," Liu and Funk write. 

"Yet bariatric surgery use remains less than 1% for patients with class 2 and 3 obesity and is even lower for patients with [type 2 diabetes] because many have class 1 obesity" and thus do not meet BMI criteria for bariatric surgery.

"Continued advocacy for bariatric surgery coverage, including expansion for patients with [type 2 diabetes] and class 1 obesity, will be critical," they conclude. "All patients deserve access to the most effective, evidence-based obesity and diabetes treatments."

This study was an initiative of PCORnet. McTigue and Liu have disclosed no relevant financial relationships. Funk was supported by a VA Health Services Research & Development Career Development Award and has received grants from the VA, National Institutes of Health, and American College of Surgeons. Disclosures for the other authors are listed in the article.

JAMA Surg. Published online March 4, 2020. Full text, Commentary

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