Discounted results from this analysis suggest that both health gains and health care cost savings are likely realized by substituting conventional therapy with surgical therapy for obese patients presenting with recently diagnosed type 2 diabetes. Strictly from a cost perspective (disregarding quality of life and life expectancy benefits of diabetes remission), this analysis suggests that after 10 years the return on investment of surgical therapy is fully recovered through savings in health care costs to treat type 2 diabetes in the surgical group.
These results underestimate the potential benefits of surgical therapy. First, this analysis captures only one benefit: the remission of type 2 diabetes. The surgical intervention also facilitated significant and sustained weight loss (mean BMI from 37 to 29 kg/m2
). The analysis did not seek to capture non–diabetes-related 1
) health care cost savings associated with a reduction in obesity-related morbidity (19
) improvements in quality of life attributable to weight loss after bariatric surgery (20
), or 3
) survival benefits of weight loss after bariatric surgery (19
). Second, the analysis did not endeavor to capture the substantial benefits from glycemic control demonstrated by surgical patients who did not achieve type 2 diabetes remission. Third, we did not apply a differential duration of diabetes remission to conventional therapy patients, despite evidence that nonsurgical interventions fail to demonstrate maintenance of weight loss over time (22
), which may correlate with faster diabetes relapse. Finally, no benefits were applied to the trial period.
Comparison with the literature
Previous studies have found surgically induced weight loss to be a cost-effective intervention for managing obesity (1
). This study finds surgically induced weight loss for managing type 2 diabetes in the obese population to be superior from an economic perspective because it is generates both cost savings and health benefits. The cost-saving result is consistent with findings from a 2008 U.S. study by Cremieux et al. (23
), which found, based on a third-party payer perspective of actual patient costs, that the initial investment in bariatric surgery was offset by downstream health care savings after 4 years.
Resource assumptions employed by our study differ from previous economic evaluations of LAGB surgery. Efficiency gains in LAGB surgery techniques are captured by adopting significantly lower (actual RCT) mean operating and admission durations. Safety gains are captured by including (actual RCT) zero operative mortality. We employed a more comprehensive approach to estimating complication rates, including all serious perioperative complications and extrapolating rates over the lifetime of patients. Optimal schedules for maintaining weight loss are captured through a rigorous postoperative follow-up schedule (20 consultations in the first 2 years and 4 per year thereafter per patient), as discussed in the associated cost-efficacy analysis (7
The transferability of diabetes remission duration results from the Greenville Series and SOS to this RCT is uncertain—the Greenville Series because research suggests that the surgical technique employed, gastric bypass surgery, contributes to diabetes remission through mechanisms independent of weight loss (24
) and the SOS study because weight loss (the driver of type 2 diabetes remission through LAGB [(6
)]) was poorly sustained, contrary to sustained weight loss anticipated for the LAGB trial population (25
). Additionally, the duration of type 2 diabetes for patients in our RCT (all recently diagnosed) was likely substantially shorter than that of the Greenville and SOS studies, which may correlate with improved diabetes remission outcomes for our trial patients.
To simulate outcomes in the period after the trial, we made assumptions about the costs, diabetes relapse rate, and mortality rate for patients in remission from diabetes. While our assumptions were based on the best available data, the possibility that some were wrong was tested by extensive uncertainty analyses.
The generalizability of cost-effectiveness results to other populations may be limited due to different intervention effects, complication rates, or health care costs. Results are only directly transferable to the clinical population with class I and II obesity and recently diagnosed type 2 diabetes in Australia.
In conclusion, the RCT demonstrated the health benefits of substantial weight loss for the obese patient with recently diagnosed type 2 diabetes. The present study shows that this benefit can be achieved with associated cost savings. Substantial weight loss should be sought in all such patients, and if nonsurgical measures are unsuccessful, the option of LAGB should be discussed.