Bariatric Surgery and Cardiovascular Outcomes

The obesity epidemic is worsening the cardiovascular health and well-being of the U.S. population.¹ Concerning trends in obesity rates across racial/ethnic groups in the United States over the past 4 decades, particularly a rising prevalence of Class III obesity (or body mass index of ≥40 kg/m²), have stymied reductions in cardiovascular disease (CVD) mortality.^2,3 Worsening CVD mortality contributes to recent reductions in overall life expectancy for U.S. adults, especially among working-aged populations.⁴ Among the available tools to combat the obesity epidemic, bariatric surgery has been shown to be one of the most effective treatments not only for weight loss in Class III obesity but also for improving cardiovascular health and outcomes. Despite a lack of randomized clinical trial data on cardiovascular outcomes after bariatric surgery, cohort studies demonstrate that bariatric surgery is associated with lower all-cause mortality and a lower risk of incident major adverse cardiovascular events for patients with Class III obesity.⁵ However, prior studies of bariatric surgery outcomes have been limited to patients with diabetes or have only included patients at specific medical centers or health care networks with limited geographic coverage of the United States.

Therefore, the study by Mentias et al⁶ published in this issue of the Journal of the American College of Cardiology provides an important addition to the literature on bariatric surgery and cardiovascular outcomes. Specifically, the authors examined the association between bariatric surgery and all-cause mortality, as well as new-onset heart failure (HF), myocardial infarction (MI), and ischemic stroke admissions in a contemporary sample of the U.S. Medicare population. The authors used exact propensity score matching to account for 87 clinical variables as potential confounders and used instrumental variable analysis as a part of sensitivity analyses to further control for unmeasured confounders.

Among a study population of more than 189,000 patients, the population was evenly divided between bariatric surgery patients and matched hospitalized control individuals, with 78% of patients in each group having Class III obesity. Patients who underwent bariatric surgery had 37% lower all-cause mortality and were significantly less likely to have admissions for new-onset HF (64% risk reduction), MI (37% risk reduction), and ischemic stroke (29% risk reduction) as compared to matched control individuals. Moreover, the number needed to treat with bariatric surgery at 3 years of follow-up to prevent death was 64 and to prevent a major cardiovascular event was 15 patients. Findings for all-cause mortality and new-onset HF and MI hospitalizations remained significant after accounting for unmeasured confounders. Importantly, in subgroup analyses, the mortality and CVD risk reductions remained significant for elderly patients (aged 65-75 years), patients without diabetes, and both men and women. This study is important because it examined a more representative sample of the general U.S. population based on race/ethnicity, age, and comorbidities than prior studies examining bariatric surgery outcomes. Critically, it provides data on the benefits of bariatric surgery in elderly populations. To date, this is one of the first studies to support bariatric surgery for CVD risk reduction in patients older than 65 years, a population at highest risk for developing HF. Interestingly, two-thirds of the Medicare population in the study were younger than 65 years of age. Therefore, the study also provides additional evidence on CVD outcomes in bariatric surgery among middle-aged men and women in the United States, a population at increasing risk for premature CVD mortality.¹

The reductions in all-cause mortality and CVD risk associated with bariatric surgery in the Mentias et al study⁶ are impressive, but more research needs to tease out contextual factors in this population and others undergoing bariatric surgery that can improve cardiovascular outcomes. For instance, what were the lifestyle or social support interventions needed for successful weight loss and CVD risk reduction in this Medicare cohort? We need to begin to consider cardiovascular outcomes from bariatric surgery when surgical procedures are a part of a multicomponent approach to obesity treatment that also includes lifestyle interventions known to improve cardiovascular health. For example, becoming more physically active post-bariatric surgery is associated with enhanced weight loss and improved health-related quality of life, and future studies should examine the cardiovascular outcomes related to bariatric surgery when coupled with physical activity.⁷ Similarly, bariatric surgery combined with intensive lifestyle intervention (ie, promoting healthful diet and physical activity) and medical management has been shown to be superior in improving cardiovascular risk factors compared to lifestyle changes and medical management alone.⁸ Therefore, future studies of diverse, representative populations, like Medicare patients or similar cohorts, should examine the additive effects on cardiovascular outcomes of insurance-funded lifestyle interventions, such as the Diabetes Prevention Program,⁹ when combined with bariatric surgery.

There is also more work needed to ensure equitable access to bariatric surgery for populations most affected by Class III obesity and CVD. Most of all, we need to consider how to reduce barriers to accessing bariatric surgery for communities of color and underresourced populations experiencing the highest obesity rates but who are the least likely to undergo bariatric procedures. Despite comparable preapproval requirements among Medicaid, Medicare, and most private insurers, Medicare and Medicaid patients are not only less likely to undergo bariatric surgery, but they are also more likely to experience postprocedure complications as compared to privately insured patients.^10,11 This underscores the significance of Mentias et al⁶ providing insights on cardiovascular outcomes among Medicare-insured bariatric surgery patients. It also calls attention to the importance of examining long-term cardiovascular outcomes after bariatric surgery in more socioeconomically-, age-, and access-diverse populations, such as those insured by state Medicaid programs, where bariatric surgery coverage is currently offered in at least 49 of 50 states and the District of Columbia.¹²

As future studies examining the relationship between bariatric surgery and cardiovascular outcomes include more representative patient samples, resource limitations related to socioeconomic status and other social determinants of health beyond in-surance coverage that threaten effective use of bariatric treatment should also be acknowledged. ¹⁰ For example, state registries reveal that Black patients experience greater postsurgical complications and lower recorded weight loss 1 year after surgery.¹³ These findings imply that there is clinical benefit of not only examining cardiovascular outcomes among surgery patients stratified by race but also identifying the role of social determinants of health in disparate cardiovascular outcomes after bariatric surgery. Ultimately, the findings of Mentias et al⁶ support future work in representative cohorts to identify and implement robust pre- and post-bariatric surgery support programs that address social determinants of obesity and improve cardiovascular health equity.