Cost-benefit analysis in health care: the case of bariatric surgery compared with diet

Purpose. The aim of the present study was to assess through a cost-benefit analysis the net monetary benefit (NMB) of bariatric surgery compared to diet (including physical exercise) for obese patients, from both the Italian payer and societal perspectives. Methods. The study considered the following groups of patients 1) patients with BMI >= 40 without complications + patients with BMI >= 35 with complications; 2) patients with BMI >= 35 and diabetes; 3) patients with BMI 30-35 and diabetes. A Markov multistate model has been developed to project the lifetime health outcomes (life years and quality adjusted life years - QALYs) and costs associated with bariatric surgery and diet for the considered groups of patients. The clinical effectiveness of each strategy was based on the likelihood of experiencing cardiovascular events or events related to the presence of diabetes. Data on clinical effectiveness, quality of life, productivity losses and out-of-pocket costs were mainly derived from the literature, while direct costs were obtained from official tariffs or literature. Different scenarios were considered for the analyses in addition to the base-case by considering utility coefficients derived from real-world data, or diabetes incidence trends after remission derived through a regression function applied to BMI values. According to both perspectives considered, the NMB has been calculated by first assuming a willingness to pay threshold (WTP=30,000€ per QALY), then converting health benefits (QALYs) into the common monetary metric (€). NMB has been calculated as (incremental benefit × WTP – incremental cost). Findings. For all the scenarios and groups of patients considered, the NMB of bariatric surgery vs. diet, on a lifetime horizon, from the payer perspective was positive and ranged from 54,647€ to 122,960€; it varied between 141,192€ to 380,286€ from the societal perspective. In the former case, the NMB turns positive after 3-4 years, indicating that bariatric surgery may be a worthy investment also in the short run for the NHS; in the latter case, for a time horizon longer than 2-3 years, the surgical option begins to show advantages for the whole society. Implications. Despite its defined cost-effectiveness, bariatric surgery is under-diffused because the initial investment for the technology is often considered a barrier. The cost benefit analysis showed that bariatric surgery, compared to diet, may be a worthwhile technology for obese patients in Italy from both payer and the broader societal perspective.