Objective: To determine how gastric bypass affects life expectancy for severely obese patients with diabetes.
Methods: We developed a decision-analytic Markov model to evaluate two treatment strategies for severely obese patients with diabetes: gastric bypass versus nonsurgical treatment. The efficacy of surgery was determined from a retrospective cohort of 165,000 severely obese diabetic patients (4,500 had gastric bypass) from 4 HMO Research Network sites using fully adjusted Cox proportional hazards models. Logistic regression models calculated in-hospital mortality for surgery using data from the Nationwide Inpatient Sample. The decision model was calibrated using data from the National Health Interview Survey and constructed using Decision Maker®, which estimated changes in life expectancy.
Results: Our base case, a 40-year-old woman with a BMI of 45 and no hypertension, coronary artery disease, or congestive heart failure, gained 7.1 years of life expectancy with gastric bypass (43.1 years with surgery vs. 36.0 without). Surgery was no longer favored in our base case when 30-day surgical mortality exceeded 16% (baseline risk, 0.2%). Sensitivity analyses revealed that gain in life expectancy decreases with increasing BMI until a BMI of 62; at this point, nonsurgical treatment achieves greater life expectancy than gastric bypass for men and women of all ages.
Conclusions: For most severely obese diabetic patients, gastric bypass surgery increases life expectancy; however, gastric bypass decreases life expectancy for those with a BMI over 62. Patients with a high BMI may receive other benefits from surgery, such as better quality of life and reduced comorbid disease.