Health and economic gains from bariatric surgery in Portugal: an in-depth analysis using a Markov model

Obesity is a chronic condition with significant health and economic impact worldwide. While conventional treatments, including dietary changes, lifestyle modifications, and non-targeted pharmacotherapy, are widely used, their long-term effectiveness in sustaining weight loss remains limited. Metabolic and bariatric surgery has shown superior clinical benefits, including comorbidity remission and increased life expectancy, but its initial cost raises concerns about its economic viability compared to non-surgical treatments. Therefore, this study assesses the long-term cost-effectiveness of bariatric surgery versus conventional treatment, considering health outcomes and economic impact within the Portuguese healthcare.

The patient journey was mapped based on clinical guidelines and adapted to the Portuguese context via stakeholder interviews. Obesity prevalence and associated comorbidities were estimated using epidemiological data. A Markov model was created to simulate obesity progression over ten, twenty years, and lifetime horizons, using monthly cycles. The model accounts for weight regain, complications, and different health states, including obesity with diabetes, cardiovascular diseases, stroke, cancer, and death. It was implemented in R Studio using heemod package. Direct healthcare costs and health outcomes were calculated. A probabilistic sensitivity analysis (PSA), with 500 iterations, was conducted to assess uncertainty.

The results demonstrate that bariatric surgery, compared to conventional treatment, enhances life expectancy, quality-adjusted life years (QALYs), and reduces obesity-related comorbidities. Over 10 years, surgery yields 6 QALYs to each patient costing 9243€, compared to 4.9 QALYs and a cost of 6328€ for the non-surgical arm. The cost-effectiveness analysis shows that, despite higher initial costs, bariatric surgery is cost-effective over time. The incremental cost per QALY gained is estimated at 2756€, positioning bariatric surgery as an economically advantageous intervention at commonly accepted willingness-to-pat thresholds (WTP). After 20 years, this strategy emerges as dominant, improving health outcomes while reducing overall costs. On the lifetime horizon, surgical patients gain 7 additional QALYs and cost 4534€ less than non-surgical patients. PSA shows that the cost-effectiveness of this strategy is maintained.

The analysis suggests that surgery is an effective strategy to improve outcomes and managing expenses. Future research should refine the model exploring upcoming treatment strategies as additional evidence on its outcomes becomes available.