Decision Modeling to Estimate the Impact of Gastric Bypass Surgery on Life Expectancy for the Treatment of Morbid Obesity

Objective: To create a decision analytic model to estimate the balance between treatment risks and benefits for patients with morbid obesity. Design: Decision analytic Markov state transition model with multiple logistic regression models as inputs. Data from the 2005 National Inpatient Survey were used to calculate in-hospital mortality risk associated with bariatric surgery and then adjusted for 30-day mortality. To calculate excess mortality associated with obesity, we used the 19911996 National Health Interview Survey linked to the National Death Index. Bariatric surgery was assumed to influence mortality only through its impact on the excess mortality associated with obesity, and the efficacy of surgery was estimated from a recent large observational trial. Intervention: Gastric bypass surgery. Main Outcome Measure: Life expectancy. Results: Our base case, a 42-year-old woman with a body mass index of 45, gained an additional 2.95 years of life expectancy with bariatric surgery. No surgical treatment was favored in our base case when the 30-day surgical mortality exceeded 9.5% (baseline 30-day mortality, 0.2%) or when the efficacy of bariatric surgery for reducing mortality decreased to 2% or less (baseline efficacy, 53%). Conclusions: The optimal decision for individual patients varies based on the balance of risk between peri-operative mortality, excess annual mortality risk associated with increasing body mass index, and the efficacy of surgery; however, for the average morbidly obese patient, gastric bypass improves life expectancy.