Bariatric surgery may enhance cardiovascular health in obese NAFLD patients

A new study revealed that bariatric surgery resulted in a nearly 50% reduction in incident cardiovascular disease and composite cardiovascular adverse events in a large cohort of obese patients with BMI >40 kg/m2 and nonalcoholic fatty liver disease compared to those who did not undergo bariatric surgery. The study results were published in the journal JAMA Network Open.  

Nonalcoholic fatty liver disease (NAFLD) is a well-known independent risk factor for CVD and CVD-related death. Although previous research has shown that lifestyle changes such as weight loss and exercise improve steatosis and metabolic markers of dyslipidemia, their success in lowering CVD risk may be limited, possibly due to the level of effort required to achieve significant improvement being difficult to maintain over time.  As the association between bariatric surgery and better CVD outcome in the obese population with a wide range of NAFLD has not been well investigated, researchers conducted a study to assess if bariatric surgery can reduce the risk of future adverse cardiovascular events in obese NAFLD patients. 

Between January 1, 2007, and December 31, 2017, insured patients aged 18-64 with NAFLD and extreme obesity (BMI >40 kg/m2) were identified in the MarketScan Commercial Claims and Encounters database. Patients having past bariatric surgery, excessive alcohol consumption, or previously identified liver illness unrelated to NAFLD were excluded from the trial. Among the remaining cohort, the surgical group included those who had bariatric surgery (sleeve gastrectomy or Roux-en-Y) during the research period, whereas the nonsurgical group included those who did not have bariatric surgery during the study period. Myocardial infarction, heart failure, or stroke were the primary composite outcomes. Ischemic cardiovascular and cerebrovascular events, CVD, and atherosclerosis were included in the secondary composite outcome. Using Cox proportional hazards modeling with inverse probability treatment weighting, bariatric surgery was compared to all outcomes as a time-varying variable. 

Key findings of the study:

• A total of 86,964 patients meeting inclusion criteria were included for analysis.
• During the study period, 30,300 (34.8%) received bariatric surgery, and 56,664 (65.2%) did not receive bariatric surgery.
• All baseline covariates available in the database and used in the analysis were balanced by Inverse probability treatment weighting. 
• Incident composite cardiovascular events occurred in 1,568 over 57,061.4 person-years in the surgical group, versus 7,215 over 96,150.1 person-years in the non-surgical group. 
• Incident difference was greater in the nonsurgical group by 4.8 events per 100 person-years.
• The surgical patients had lower adjusted hazards of myocardial infarction; heart failure; and ischemic stroke when compared to nonsurgical patients.
• There was a 49% reduced risk of any CVD outcome in the surgical group compared to the nonsurgical group by the end of the study period. 
• Compared to the nonsurgical group, the bariatric surgical group had a primary composite CVD outcome reduction of 47%, and a secondary composite CVD outcome reduction of 50%.
• Sensitivity analysis, which looked at the possibility that unmeasured confounders may change the statistical data, demonstrated a consistent and substantial link between bariatric surgery and better clinical outcomes.
• The E-value analysis, on the other hand, revealed that an unmeasured confounder with HR 2.56 may give a different explanation for the study's primary findings.

Thus, despite the allocation bias and numerous unmeasured confounders, the study data showed a strong correlation between bariatric surgery and improved cardiovascular outcomes. 

Further reading: Association of Bariatric Surgery With Cardiovascular Outcomes in Adults With Severe Obesity and Nonalcoholic Fatty Liver Disease. JAMA Netw Open 2022;5:e2235003. Doi: 10.1001/jamanetworkopen.2022.35003