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In patients with type 2 diabetes (T2DM), outcomes of Roux-en-Y gastric bypass (RYGB) surgery were better than sleeve gastrectomy (SG), a finding at odds with recent randomized clinical trials, authors of a large cohort study said.

In nearly 10,000 patients followed for up to 5 years, weight loss was significantly greater with RYGB than SG at 1 year (mean difference 6.3 percentage points, 95% CI 5.8-6.7) and 5 years (mean difference 8.1 percentage points, 95% CI 6.6-9.6), researchers led by Kathleen McTigue, MD, of the University of Pittsburgh, reported online in .

The T2DM remission rate at 5 years was approximately 10% higher in those who underwent RYGB (86.1% vs 83.5%, HR 1.10, 95% CI 1.04-1.16). Among those who experienced remission, the risk of subsequent relapse was significantly lower for RYGB (HR 0.75, 95% CI 0.67-0.84), McTigue's group reported.

Finally, glycemic control was also better with RYGB. At 5 years, hemoglobin A1c (HBA1c) was reduced by a mean of 0.45 percentage points (95% CI 0.27-0.63) more for patients who had RYGB versus those who had SG, the study found.

"The comparison is particularly salient because SG has begun to supplant RYGB as the dominant bariatric procedure over the past decade, despite limited long-term comparative data," McTigue and colleagues wrote. Two recent randomized clinical trials, and , reported no significant difference in weight loss between the two procedures in patients with morbid obesity, significant proportions of whom had T2DM (approximately 42% in SLEEVEPASS and 26% in SM-BOSS.)

Those trials had much smaller sample sizes, 240 patients in SLEEVEPASS and 217 in SM-BOSS, which may have limited their power to detect differences between the procedures, the researchers noted. "Also, patients who are willing to undergo randomization between RYGB and SG and surgeons who have equal skill and equipoise for RYGB and SG are likely different from those who choose either RYGB or SG in uncontrolled settings."

"Thus, while the more rigorous, randomized clinical trial data indicate that RYGB and SG perform similarly in highly controlled environments, in everyday practice, the outcome differences may be larger," the team wrote.

McTigue's group analyzed data on 9,710 adult patients with T2DM in the National Patient-Centered Clinical Research Network Bariatric Study, which included 34 sites in the U.S. These patients underwent bariatric surgery from January 2005 through September 2015. Mean age was 49.8, nearly three-quarters were both white and female, and mean body-mass index was 49.

The researchers analyzed electronic medical records for these patients, which included ICD-9 codes, Systematized Nomenclature of Medicine codes, and demographic information. The main outcomes included percentage of total weight loss, diabetes remission and relapse, and change in HBA1c.

Noting that the outcomes were good with both procedures, McTigue and colleagues said their study results suggest RYGB may especially benefit patients who are less likely to achieve remission with bariatric surgery, including older patients, those with higher baseline HBA1c, and those on insulin and more complex T2DM medication regimens.

"Our findings indicate that patients with lower preoperative probability for T2DM remission (11%- 33%) may be more likely to achieve T2DM remission with RYGB compared with SG. Estimating the likelihood of T2DM remission could help inform patients' and clinicians' discussions of procedure choice," the researchers wrote.

In , Natalie Liu, MD, and Luke Funk, MD, both of the University of Wisconsin School of Medicine and Public Health in Madison, said the study provided important information despite certain limitations. "Although there were limitations -- including possible inaccuracies in electronic health record diagnostic and medication codes and confounding that was not accounted for -- this analysis is an important contribution. It included long-term electronic health record data from a large cohort of U.S. patients who had bariatric surgery in a real-world setting."

"Although both RYGB and SG were associated with high rates of T2DM remission, a considerable number of patients relapsed, particularly following SG," Liu and Funk continued. "Given that the drivers of diabetes relapse after bariatric surgery are unclear, further investigation into this phenomenon is needed."

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