Bariatric Surgery Reduces Hard CVD Events in Obese Patients With Type 2 Diabetes

Bariatric weight-loss surgery for obese patients with type 2 diabetes lowers the risk of coronary artery and cerebrovascular disease compared with the traditional management approach for diabetes that includes medication and lifestyle modification, according to the results of a new study. 

In a retrospective cohort study of adults with obesity and type 2 diabetes, bariatric surgery was associated with a 40% lower risk of macrovascular events—defined as the first occurrence of a coronary artery disease or cerebrovascular event—at 5 years when compared with matched patients treated with usual diabetes care. Bariatric surgery was also associated with a 36% lower risk of coronary artery disease events, a composite that included ACS, unstable angina, or revascularization with PCI or CABG surgery.

“This is no longer an experimental question,” David Arterburn, MD (Kaiser Permanente Washington Health Research Institute, Seattle), the study’s corresponding author, told TCTMD. The evidence supporting “the notion that bariatric surgery is beneficial for patients with obesity and type 2 diabetes is incontrovertible.”

For patients with severe obesity and type 2 diabetes, said Arterburn, treatment options are limited, since many of these individuals have physical restrictions that limit their ability to lose weight through lifestyle modification, particularly exercise. However, randomized trials have shown bariatric surgery is more effective than medication and/or lifestyle modification for weight loss, improving glycemic control and cholesterol levels, as well as controlling diabetes, hypertension, and dyslipidemia..

“You can continue to bombard them with additional medication, including insulin, to try reduce their risk, but most of the medications have weight gain as one of the side effects,” said Arterburn. “You’re essentially contributing to the problem of severe obesity while actively treating it.”

Reduction in CAD and All-Cause Mortality

The study, which was published October 16, 2018, in JAMA, included 20,235 patients with severe obesity—defined as a body mass index (BMI) ≥ 35 kg/m2—and type 2 diabetes. This included 5,301 individuals who underwent bariatric surgery between 2005 and 2011 in four US healthcare systems and 14,934 control subjects matched by site, age, sex, BMI, hemoglobin A1c, insulin use, diabetes duration, and prior health care utilization. The majority of surgical patients were treated with Roux-en-Y gastric bypass, 17% with sleeve gastrectomy, and 7% with adjustable gastric banding, while the control subjects were treated with usual care for diabetes. 

Over a median follow-up of 4.7 years, there were 106 macrovascular events (37 cerebrovascular and 78 coronary artery disease events) among patients treated with surgery and 596 events (227 cerebrovascular and 398 coronary artery disease events) in the patients treated with usual care. The incidence of macrovascular events was 2.1% in the surgical arm and 4.3% in the usual-care group, a statistically significant difference. Bariatric surgery was associated with a significantly lower incidence of coronary artery disease events—1.6% with surgery versus 2.8% in nonsurgical arm—but there was no difference in the incidence of cerebrovascular disease.

In a post hoc analysis, mortality rates were also significantly lower among those treated with surgery. At 1, 3, 5, and 7 years, the rates of death were 0.4%, 0.9%, 1.3%, and 2.0%, respectively, in the surgical arm. Comparatively, the respective rates were 0.9%, 2.7%, 4.5%, and 6.4% in the nonsurgical arm. This translated into a 67% reduction in the risk of all-cause mortality with surgery at 5 years compared with usual care.

“There are concerns about the risks of surgery, but they need to be placed in the context of the risk of continuing to live with severe obesity and diabetes,” said Arterburn. “If you have severe obesity and diabetes, you’re much more likely to die from those conditions than you are from having surgery. That’s what this study suggests. This evidence adds to other evidence suggesting that bariatric surgery reduces the risk of mortality and a lot of other evidence around the improvement in blood sugar and diabetes outcomes.”

Haitham Ahmed, MD (Cleveland Clinic, OH), who was not involved in the study, said the combination of obesity and type 2 diabetes is problematic because the two conditions feed into each other: obesity leads to hyperglycemia and insulin resistance, which then further results in deposition of excess fat. The ideal first line of attack is to reduce body weight in order to be able to treat the metabolic disorder.

For patients with severe obesity and type 2 diabetes, Ahmed said he would take an aggressive approach with surgical weight loss. However, “surgery is not a magic fix,” he added. “Surgery really needs to be accompanied by dietary changes, a steady exercise regimen, and changes to one’s entire lifestyle.”

That said, Ahmed noted that physicians do recognize the inherent challenges in treating these patients and aren’t opposed to recommending surgery.

“Weight loss leads to significant improvements in metabolic measures, such HbA1c levels, blood pressure, and cholesterol levels, among others, so the fact that this leads to downstream reductions in clinical events, including cardiovascular outcomes, isn’t surprising,” said Ahmed.

Both Arterburn and Ahmed noted that these new data are supported by findings from European studies, specifically the Swedish Obesity Study. In that study, which included a subset of patients with obesity and type 2 diabetes, there was a reduction in cardiovascular outcomes among patients undergoing bariatric surgery when compared with those treated with usual care.

“The big contribution of [the new report] is that there really haven’t been any US-based studies with a large enough sample of patients to look at the long-term question,” said Arterburn, referring macrovascular benefits of bariatric surgery. Moreover, patients treated in the present study were treated with modern-day bariatric procedures compared with the Swedish Obesity Study that largely including more gastric banding.

Is More Study Needed?

Although the analysis is observational, Ahmed doesn’t believe a randomized clinical trial comparing bariatric surgery versus usual care would be necessary or feasible.

“I’m not sure a randomized trial would be possible given the numbers that would be needed to sufficiently power such a trial for cardiovascular outcomes,” said Ahmed. “That’s why these types of large, pooled, observational studies are very important.” Moreover, the reduction in clinical events is “biologically plausible” given the historic data showing metabolic improvements—HbA1c level, blood pressure, and cholesterol levels—following bariatric surgery, he said, and these changes are known to impact cardiovascular disease outcomes.

For Arterburn, there are still some things to figure out, such as which patients do better with surgery, how to help patients keep weight off long-term, and how to deal with long-term complications that might arise from surgery, but he said the bottom line is that, on average, “these patients are going to be living longer and having fewer diabetes-related complications.”

In an editorial, Adam Sheka, MD, Keith Wirth, MD, and Sayeed Ikramuddin, MD (all from the University of Minnesota, Minneapolis), state that for the prevention of macrovascular events, “the societal benefits of aggressive medical therapy for diabetic control are modest and the costs are great.” And even though there is “relatively weak evidence supporting aggressive medical management of type 2 diabetes for reducing cardiovascular events and mortality, evidence for the benefits of bariatric surgery for improving these outcomes is increasing.”

The editorialists point out that access to bariatric surgery is currently limited by insurance companies, lack of Medicaid coverage in some states, and high out-of-pocket costs. “Given the benefits of bariatric surgery for patients with type 2 diabetes, including potentially greater long-term benefits than most pharmaceuticals, insurance coverage for weight-loss operations should be expanded for appropriate patients,” they write.