The Public Health Implications of the Cost-Effectiveness of Bariatric Surgery for Diabetes

B ariatric surgery is one of the major breakthroughs in diabetes care to have emerged since the discovery of insulin. In the 15 years since the first observational study, clinical trials and observational studies of bariatric surgery in diabetic patients have confirmed the beneficial effects of surgery (1). Since 2000, guidelines from the National Institutes of Health (NIH) have recommended bariatric surgery as an option for obesity treatment in adults with a BMI 35 kg/m and a serious comorbid condition (2). In 2009, the Centers for Medicare & Medicaid Services officially announced it would cover bariatric surgery for beneficiaries with morbid obesity and type 2 diabetes. While bariatric surgery can be beneficial, it is an expensive intervention costing at least $13,000 in the first year (3). In light of its high costs and potential benefits, understanding the cost-effectiveness of bariatric surgery for diabetes is critical for policy discussions regarding any ongoing or additional public health investment in bariatric surgery. The cost-effectiveness of bariatric surgery for diabetes has been evaluated in prior studies, but these studies have been limited by simplistic diabetes models (4–6) with parameter inputs derived from individual trials (5). Only one previous study of Roux-en-Y gastric bypass has accounted for the future complications of diabetes (7,8), and only one study has been conducted from the perspective of the U.S. (7). In this issue of Diabetes Care, Hoerger et al. (9) address many of these deficits in the existing literature and report on the most rigorously conducted costeffectiveness analysis of bariatric surgery for diabetes to date. Using the Centers for Disease Control-Research Triangle Institute (CDC-RTI) Diabetes Cost-Effectiveness Model, the authors modeled the potential lifetime effects of bariatric surgery on diabetes by estimating rates of diabetes remission and relapse, as well as diabetes complications, deaths, costs, and quality-adjusted life-years (QALYs). The authors separately evaluated two forms of bariatric surgery, gastric bypass and gastric banding, which differ in surgical approach, clinical benefits, and adverse consequences. They also accounted for the well-known differences in diabetes remission from surgery based on duration of diabetes and type of surgery. The authors found that bariatric surgery, based on currently available data, is cost-effective over the lifetimes of severely obese patients with diabetes. Bypass surgery had incremental cost-effectiveness ratios (ICERs) of $7,000/QALY and $12,000/QALY for severely obese patients with newly diagnosed and established diabetes; banding surgery had slightly higher ICERs of $11,000/QALY and $13,000/QALY for the two respective diabetic groups. The ICERs for both surgeries are very favorable since values below the $200,000/QALY threshold in the U.S. are now considered cost-effective (10). Other diabetes treatments, such as intensive glycemic and lipid control in comparison to conventional risk factor control, have previously been found to have ICERs of $41,384/QALY and $51,889/QALY (11). While these results are extremely promising for bariatric surgery, the validity of this analysis and others like it depends on the quality of the research in bariatric surgery. Unfortunately, bariatric surgery studies (12) are plagued by inadequate patient retention and short durations of follow-up. The accepted standard for patient retention in both published studies and clinical practice is 50%, which is far below the norm for clinical studies in other areas of medicine. These low retention rates are highly problematic because they have the potential to introduce strong selection bias. Patient attrition after bariatric surgery is very likely related to satisfaction with the surgery and its effects. Thus, reported results from bariatric surgery likely overestimate rates of diabetes remission and improvement and underestimate costs. In conjunction with the practice of allowing low retention rates, follow-up time for the majority of bariatric surgery studies is less than 2 years (12). This short duration of follow-up is thought to be appropriate for most surgical research since complications usually occur within a few years of surgery. However, bariatric surgery can also cause lifelong side-effects such as nutritional deficiencies, dumping syndrome, cholelithiasis, and long-term operative complications, which may be underrepresented in short-term studies (13,14). The need for studies of the long-term effects of bariatric surgery is well-known, and efforts are being made to address it. In 2005, the Longitudinal Assessment of Bariatric Surgery project was launched under direction of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). In addition, both the American Society for Bariatric Surgery and the American College of Surgeons are actively collecting data from their approved bariatric surgery centers (15,16). At present, longterm data on bariatric surgery are limited to the Swedish Obesity Study and a few small trials. Despite the limitations of bariatric surgery literature, this analysis provides a strong argument for the economic value of bariatric surgery as a treatment for diabetes in the U.S. If bariatric surgery is indeed a cost-effective treatment for diabetes in the U.S., can bariatric surgery practically be provided to everyone who would benefit from it? Should bariatric surgery be strongly advocated for these patients? One fundamental issue that may hinder the widespread adoption of bariatric surgery for diabetes is that it may simply be considered too expensive in the face of current health care budget concerns. The study by Hoerger et al. shows that bariatric surgery for diabetes is costeffective over the lifetime of the patient, which means that adoption of bariatric surgery will increase health care costs. These cost concerns are undoubtedly shared by individual payers who have been reluctant to adopt widespread coverage of the procedure (17). The payer perspective is important for bariatric surgery because the majority of the costs ocE d i t o r i a l s