Five-year direct medical costs and comorbidities after bariatric surgery of obese patients with type 2 diabetes mellitus: A population-based propensity score-matched study

Abstract Background: Bariatric surgery is effective in weight reduction and diabetes remission. This study aimed to estimate direct medical costs and changes of comorbidities after bariatric surgery up to five years among obese patients with type 2 diabetes mellitus. Methods: A population-based retrospective cohort of obese type 2 diabetes patients from Hong Kong Hospital Authority between 2006 and 2017 was assembled. One-to-five propensity score matching method was applied to match 401 eligible surgical patients with 1,894 non-surgical patients. Frequency of healthcare service utilization and dispense of diabetes medication were collected for both groups to estimate the direct medical costs from baseline to up to 60 months; Charlson Comorbidity Index (CCI) and number of comorbidities were measured to compare the changes of comorbidities between two groups over the 5 years. Results: Direct medical costs were US$40,889 for surgical patients and US$6,163 for controls in the index year (p<0.001), with incremental costs of US$34,726. Bariatric surgery and hospitalization were the main cost drivers for surgical patients in the year of surgery. Although surgical patients had significantly lower annual costs than control patients in the subsequent four years, five-year cumulative costs incurred by surgical patients were significantly greater than controls (US$60,174 vs US$33,374, p<0.001), regardless of subgroups. Surgical patients had better profile of comorbidities than controls, as they had significantly lower CCI after baseline and fewer percentages of them proceeded to higher CCI categories. Conclusions: Over 5 years, bariatric surgery was associated with increased medical costs in the year of surgery and cumulative costs. Although bariatric surgery is not cost-saving for type 2 diabetes patients at 5 years, it is associated with improved comorbidity profile.