Sensitivity Analysis

Sensitivity analysis was performed by comparing outcomes between the BS cohort and the ‘bariatric procedure qualifying’ cohort. Patients with no history of bariatric surgery but with clinical attributes that would qualify for these procedures were identified and included in the ‘bariatric procedure qualifying’ group (BMI ≥ 40 or if they had BMI ≥ 35 with the presence of a co-morbid condition including hypertension, diabetes mellites type 2, hyperlipidemia, ischemic heart disease or heart failure, or obstructive sleep apnea). After unmatched crude analysis, two propensity score-matched analyses were performed. Propensity score-matched analysis was first performed by matching propensity scores incorporating demographic variables and lower respiratory disease only, with no matching performed for metabolic diseases and BMI, to prevent bias resulting from inadvertent control of effects of bariatric surgery. Subsequently, a matched analysis was performed between these cohorts with all the abovementioned covariates (age, race, gender, BMI, diabetes, hypertension, chronic lung diseases, nicotine dependence, heart failure, and ischemic heart disease).