Economic impact of bariatric Surgery in Australia: 16-year results from the 45 and up study with linked health data

Background: Bariatric surgery is the most effective long-term therapy for severe obesity; however, empirical investigation of its economic impacts has been based on limited samples, short-term costs, and a narrow range of cost categories. This study aimed to evaluate the economic impacts of bariatric surgery in a large cohort of Australians aged ≥ 45 years. Methods: N = 1157 operated (surgery) and 1157 non-operated participants were selected from the 45 and Up Study. Data sources included the baseline and follow-up surveys along with linked state and national administrative health datasets. Linear mixed-effects regression predicted the cost trajectory 8 years pre- and post-bariatric surgery, and the difference-in-differences approach evaluated its economic impact. Sensitivity analyses included an approximation of indirect costs and subgroup analysis by surgery type. Results: The matched cohort composed 77% female, had an average age of 58.1 ± 5.8 years. Direct healthcare costs increased over time in both groups. Costs for the operated group peaked ($15,884) during the surgery year and became up to 23.8% lower than those for the non-operated group from the second year post-surgery when including indirect costs. Surgery's economic benefits increased over longer horizons, with a maximum annual cost-saving of $3196 per person in the eighth post-surgery year. However, even after accounting for indirect costs, cumulative cost-savings were not achieved. Subgroup analysis revealed sleeve gastrectomy as the least costly surgical option. Conclusion: Higher short-term costs in the surgery year primarily drove inter-group cost differences. The economic value of bariatric surgery lies in the long-term benefits, particularly when considering indirect costs.