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Analysis

Metabolic Surgery Linked to Significantly Lower Risk of Cardiovascular Disease

By Christopher Cheney  
   September 23, 2019

Researchers have associated metabolic surgery with lower risk for all-cause mortality, coronary artery events, cerebrovascular events, heart failure, nephropathy, and atrial fibrillation.

Metabolic surgery in patients with obesity and type 2 diabetes results in significantly lower risk of major adverse cardiovascular events, recent research indicates.

From 2015 to 2016, 39.8% of Americans over age 20 were obese, according to the Centers for Disease Control and Prevention (CDC). For the same time period, 20.6% of adolescents were obese, the CDC says. In 2008, the estimated annual medical cost of obesity was $147 billion.

The stakes are high for people with obesity and type 2 diabetes, according to the co-authors of the recent research, which was published in the Journal of the American Medical Association. "In patients with obesity and type 2 diabetes, weight and glycemic goals are difficult to achieve through usual care including lifestyle modifications and pharmacotherapy. In patients with obesity and diabetes, cardiovascular disease is the major cause of morbidity and mortality," they wrote.

Cardiovascular impact of metabolic surgery by the numbers
 

The recent research features data collected from more than 13,000 patients—2,287 patients who underwent metabolic surgery and 11,435 patients in a control group that did not have surgery. The primary focus was the incidence of six major adverse events: all-cause mortality, coronary artery events, cerebrovascular events, heart failure, nephropathy, and atrial fibrillation.

Most of the metabolic surgical procedures were Roux-en-Y gastric bypass (63% of patients) and sleeve gastrectomy (32%).

The research generated several key data points:

  • 30.8% of patients in the metabolic surgery group experienced major adverse events after their operations compared to 47.7% in the nonsurgical control group
     
  • All-cause mortality occurred in 10.0% of patients in the metabolic surgery group compared to 17.8% in the nonsurgical group
     
  • After following patients for eight years, mean body weight was reduced by 29.1 kg in the surgery group and 8.7 kg in the nonsurgical group
     
  • Utilization of noninsulin diabetes medications, insulin, hypertensive medications, lipid-lowering therapies, and aspirin were significantly lower for the surgery group compared to the nonsurgical group
     
  • Complications after metabolic surgery were relatively low, including bleeding requiring transfusion in 3.0% of patients, pulmonary adverse events in 2.5% of patients, venous thromboembolism in 1.0% of patients, cardiac events in 0.7% of patients, and renal failure requiring dialysis in 0.2% of patients

"All six prespecified outcomes were significantly lower in the surgery group, including all-cause mortality, coronary disease events, cerebrovascular events, heart failure, atrial fibrillation, and nephropathy," the JAMA researchers wrote.

Interpreting the research
 

The research team speculated that substantial and sustained weight loss after metabolic surgery led to a lower prevalence of major adverse cardiovascular events. "It's the most obvious conclusion," one co-author told HealthLeaders.

"You do metabolic surgery, and people lose a lot of weight. We know obesity is associated with cardiovascular risk enhancement from increased cholesterol, increased blood pressure, and higher incidence of diabetes. So, if you make the obesity better, it stands to reason that you would expect rates of cardiovascular disease to go down," said Steven Nissen, MD, professor of medicine, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University, Cleveland.

The magnitude of the cardiovascular benefits of metabolic surgery was unexpected, he said.

"This is a huge treatment effect. It was possible that the adverse cardiovascular prognosis from obesity would be largely irreversible. In other words, once people were obese, you would have a hard time reversing their cardiovascular event rate. That was not what we saw. There was a 39% reduction in six component adverse cardiovascular events and a 41% decreased risk of all-cause mortality. Those are really large effects," Nissen said.

Despite the eye-popping results, it is unreasonable to expect that metabolic surgery alone can end the country's obesity epidemic, he said.

"There are tens of millions of people in America who have severe obesity, and we cannot do surgery in all of them. Last year, about 250,000 people underwent bariatric surgery. Studies like ours will increase the number of people who are offered the operation. … It is a therapy that can be utilized in more people, but it is not going to completely fix the obesity epidemic because it just is not practical to do the operation in everybody who is obese."

More research is needed to confirm the JAMA study's findings, Nissen said.

"We recognize there are limitations of our study. It is an observational study, not a randomized controlled trial. We think that our findings make it imperative that we do a large randomized controlled trial, and we are working on securing the necessary funding to do that. We need to nail down for certain what these benefits are and what the risks are in a randomized controlled trial."

Christopher Cheney is the senior clinical care​ editor at HealthLeaders.


KEY TAKEAWAYS

In the United States, the annual medical costs associated with obesity have been estimated at $147 billion.

Recent research found that all-cause mortality occurred in 10.0% of patients in the metabolic surgery group compared to 17.8% in the nonsurgical control group.

After following the patients for eight years, mean body weight was reduced by 29.1 kg in the surgery group and 8.7 kg in the nonsurgical group.

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