Background
Obesity is a cardinal risk factor for the development of atherosclerotic cardiovascular disease. Bariatric surgery is an effective method of achieving weight reduction and improving control of cardiovascular risk factors in patients with obesity. However, the effect of bariatric surgery on long-term cardiovascular outcomes has yet to be defined.

Purpose
The aim of this study is to evaluate the effect of bariatric surgery on long-term risk of major adverse cardiovascular events in a large population of patients with obesity.

Methods
A nested cohort study was carried out; including the 3,701 patients of the Clinical Practice Research Datalink database who had undergone bariatric surgery, and 3,701 age, gender and BMI matched controls. The primary endpoint was the composite of fatal or non-fatal myocardial infarction; and fatal or non-fatal acute ischaemic stroke. Secondary endpoints included all-cause mortality, new diagnosis of heart failure, fatal or non-fatal myocardial infarction, and fatal or non-fatal acute ischaemic stroke. Data was analysed using a Cox proportional hazards model to account for multiple covariates.

Results
Patients were followed up for a median of 11.2 years; 20.3% of the population were female, the median age was 36 years and median BMI was 40.4 kg/m2. Patients who had undergone bariatric surgery had a significantly lower occurrence of the primary composite outcome (HR 0.450; 95% CI 0.312–0.671, p<0.001, NNT=62); this was driven by a reduction in myocardial infarction (HR 0.444; 95% CI 0.302–0.654, p<0.001, NNT=64) and not in acute ischaemic stroke (HR 0.528; 95% CI 0.159–1.751, p=0.296). A significant reduction was observed in rates all-cause mortality (HR 0.254; 95% CI 0.183–0.353; p<0.001, NNT=27) and of new diagnosis of heart failure (HR 0.519; 95% CI 0.311–0.864, p=0.012, NNT=153).
Conclusion
The results of this large, nation-wide nested cohort study support the role of bariatric surgery in reducing the risk of major cardiovascular events, all-cause mortality and new onset of heart failure in patients with obesity.