OBJECTIVES: To provide real-world evidence regarding the economic impacts of bariatric surgery from a large Australian cohort.

METHODS: In this longitudinal population-based cohort study based in the state of New South Wales, Australia, 1,157 subjects undergoing bariatric surgery (the operated group) were drawn from the Sax Institute’s 45 and Up Study (between 2006 to 2009) and exactly matched with 1,157 non-operated subjects. Data sources included the baseline and follow-up surveys and linked national administrative datasets. Linear mixed-effects model was used to predict the cost trajectory 8 years before and 8 years after surgery, and difference-in-differences approach was chosen to evaluate surgery’s economic impacts. Sensitivity analysis by including an approximation of indirect costs and subgroup analysis by surgery type were performed.

RESULTS: The average age of the matched cohort was 58.1±5.8 years and 77% were female. The direct costs in both the operated and non-operated group increased over time. Costs in the operated group peaked during the surgery year, and then substantially decreased towards those of the non-operated group from the second year after bariatric surgery. When estimated indirect costs were modelled, the combined costs for the operated group were lower than those for the non-operated group from the second year after surgery. Whilst surgery’s economic benefits increased over longer horizons, cumulative cost-savings were not achieved during the study period even after the consideration of indirect costs. Subgroup analysis revealed that sleeve gastrectomy is the lowest cost surgical option.

CONCLUSIONS: The short-term higher costs in the year of surgery were the main driver of inter-group cost differences. The cost differences between those with or without bariatric surgery decreased over longer time horizons, particularly when indirect costs were considered. Future longer-term studies including younger Australians from multiple locations, and a comprehensive range of obesity-related costs are needed.