Body mass index and risk of mortality in patients undergoing bariatric surgery

Prior literature has demonstrated that bariatric surgery is a safe approach for patients with morbid obesity. However, the relationship between body mass index (BMI) and risk of mortality in these patients has not been fully elucidated. Primary objective of this study was to evaluate the relationship between BMI and risk of mortality using data obtained from a national database, with a special focus on patients with BMI ≥ 70.0 kg/m².

A retrospective cohort study of patients with morbid obesity (BMI ≥ 40 kg/m²) undergoing first-time bariatric surgery between 2015 and 2018 was performed using data from the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program. Primary outcome was intra-operative death or death within 30 days post-operatively. Patients were categorized into quartiles according to BMI. Multivariable analysis was performed to evaluate the association of BMI with risk of mortality. Relative risk (RR) and 95% confidence interval (CI) are provided as measures of strength of association and precision, respectively.

A total of 463, 436 patients were included with a 30-day mortality rate of 0.11%. Mean BMI (SD) was 48.2 (7.3) kg/m²; 1.5% of patients had BMI ≥ 70.0 kg/m². On multivariable analysis, highest quartile patients had a significantly higher risk of mortality than lowest quartile patients. For patients with BMI ≥ 70.0 kg/m², the risk of mortality was more pronounced with an eightfold increase compared to the lowest quartile. In patients with BMI ≥ 70.0 kg/m², although sleeve gastrectomy (SG) was the most common procedure, the risk of mortality was significantly higher in patients undergoing Roux-en-Y gastric bypass (RYGB).

BMI is associated with increased risk of 30-day mortality. The effect of BMI is more pronounced in patients with BMI ≥ 70.0 kg/m². In these patients, RYGB is associated with increased risk of mortality compared to SG.