Gastric Bypass Benefits for Diabetic Heart Complications Can Fade

After five years, about half of recipients held onto cardiovascular benefits

For obese people with diabetes, doctors have increasingly been offering gastric bypass surgery as a way to lose weight and control blood glucose levels. Short-term results are often impressive, but questions have remained about the long-term benefits of such operations. Now, a large, international study has some answers.

Soon after gastric bypass surgery, about 50% of folks not only lost weight but also showed well-controlled blood glucose, cholesterol, and blood pressure. The good news is that five years later, about half of those who originally showed those broad benefits of surgery maintained that healthy profile. The not-so-good news is that the other half, while they generally continued to sustain weight loss and better glucose control, began to show signs of increasing risk for cardiovascular complications.

Earlier studies have consistently shown that gastric bypass surgery offers benefits in terms of weight loss and improved blood glucose control for people with diabetes. But diabetes also comes with an increased risk for cardiovascular complications. People with diabetes are at greater risk of suffering a heart attack or stroke. They are also more likely than people without diabetes to have other cardiovascular risk factors, including high blood pressure and cholesterol levels. Does gastric bypass help to reduce those risks too?

That’s the question the NIH-funded Diabetes Surgery Study set out to answer about a decade ago. To get a more holistic view on the benefits of gastric bypass surgery, they relied on the American Diabetes Association’s (ADA’s) composite triple endpoint for diabetes. Those guidelines include a hemoglobin A1C of less than 7%. The A1C test measures the amount of glucose attached to hemoglobin in red blood cells, which reflects a person’s average blood glucose level in the preceding months. An A1C below 5.7% is considered normal. An A1C above 6.5 is consistent with a diagnosis of diabetes.

In addition, the ADA’s composite end point includes a low-density lipoprotein or “bad” cholesterol level of less than 100 mg/dL and systolic blood pressure less than 130 mmHg. For people with diabetes, the triple endpoint is often remarkably tough to achieve; most never do.

Led by Sayeed Ikramuddin and Charles Billington at the University of Minnesota, Minneapolis, the Diabetes Surgery Study enrolled 120 people in the United States and Taiwan who had type-2 diabetes and a hemoglobin A1C above 8%. All participants also had a body mass index (BMI) above 30, which is generally considered obese. Half of the study’s participants were randomly selected to undergo a Roux-en-Y gastric bypass procedure along with two years of intensive lifestyle and medical management. The remaining study participants received two years of intensive lifestyle and medical management without surgery.

The Roux-en-Y procedure involves reducing the stomach size by 90% and attaching the remaining stomach pouch into a latter section of the small intestine. As a result, people eat less and absorb fewer calories. The question was: Would that surgical procedure, when added to those other interventions, help more people to reach and maintain the ADA’s triple endpoint?

As reported in JAMA, the initial results were quite encouraging. In the first year, half of the gastric bypass group (28 people) achieved the composite triple endpoint. That’s compared to 16% of those (9 people) who didn’t undergo surgery. However, that early success began to slip by year three. By that time, 23% of those in the gastric bypass group compared to 4% in the lifestyle-medical management group met the goals for blood glucose, cholesterol, and blood pressure.

The five-year outcomes data now show that those improvements seen at year three have held steady, with those who received a gastric bypass continuing to fare significantly better on average than those who received the lifestyle and medical intervention alone. However, the diminished magnitude of those effects raises doubts about the procedure’s longer-term benefits to prevent cardiovascular disease.

Further study is needed to determine the continued durability of those improvements and whether they will ultimately translate into fewer cardiovascular complications, including heart attack and stroke. In weighing those benefits, it’s also important to note that some people have suffered serious adverse events after gastric bypass, including small bowel obstructions and leaks.

Source: National Institutes of Health; January 23, 2018.