Benefits of gastric bypass may diminish after 5 years

Patients with type 2 diabetes who had Roux-en-Y gastric bypass surgery maintained significant, although shrinking, improvements in HbA1c compared to those receiving lifestyle and medical management.

Patients who had Roux-en-Y gastric bypass surgery maintained significant improvements in HbA1c after five years compared to those receiving lifestyle and medical management, but with diminishing differences, a study found.

Researchers conducted an observational follow-up study of a randomized clinical trial that included 120 participants (mean age, 49 years) at four sites in the United States and Taiwan. At baseline, patients had an HbA1c level of 8.0% or higher and a body mass index between 30.0 and 39.9 kg/m2. Patients underwent lifestyle-intensive medical management intervention based on the Diabetes Prevention Program and Look AHEAD (Action for Health in Diabetes) trials for two years, with half undergoing Roux-en-Y gastric bypass surgery.

Main outcomes included a composite triple end point of HbA1c level less than 7.0%, low-density lipoprotein cholesterol level less than 100 mg/dL (2.6 mmol/L), and systolic blood pressure less than 130 mm Hg. Of 120 participants who were initially randomized, 98 (82%) completed five years of follow-up. At five years, 13 participants (23%) in the gastric bypass group and 2 (4%) in the lifestyle-intensive medical management group had achieved the composite triple end point (difference, 19%; 95% CI, 4% to 34%; P=0.01). In the fifth year, 31 patients (55%) in the gastric bypass group compared to 8 (14%) in the lifestyle-medical management group had an HbA1c level less than 7.0% (difference, 41%; 95% CI, 19% to 63%; P=0.002). Results were published Jan. 16 by JAMA.

The gastric bypass group had more serious adverse events than did the lifestyle-medical management group: 66 events compared to 38 events, most frequently gastrointestinal events and surgical complications such as strictures, small bowel obstructions, and leaks. Gastric bypass patients also had more parathyroid hormone elevation but there was no difference in B12 deficiency.

The researchers noted that the improvements in the composite end point associated with gastric bypass diminished over time. Most of the reduction in the proportion of participants achieving the primary end point was between years 2 and 3, after which the effects of both strategies remained relatively constant.

“Worsening metabolic control over 5 years despite weight loss durability, particularly in the gastric bypass group with greater weight loss, indicates that improving diabetes control for the long-term may involve other factors, notably the health of pancreatic beta cells,” the authors wrote. “There may have been insufficient beta cell function in some participants to maintain long-term diabetes improvement. Whether such a possibility supports earlier surgical intervention for diabetes will need to be evaluated in other studies.”