Cost of illness analysis in individuals with overweight or obesity and chronic low back pain in the Bern metropolitan area (the BO2WL trial).

Background: Chronic low back pain (CLBP) imposes substantial societal costs, with comorbid overweight or obesity possibly further increasing them. This study assessed the cost of illness of individuals with CLBP and comorbid overweight or obesity in the Bern metropolitan area (Switzerland) from a societal perspective. Methods: Following the Consolidated Health Economic Evaluation Reporting Standards 2022 and using preliminary baseline data from a randomised controlled trial, societal costs, including direct and indirect costs, over 3 months were calculated for adults with overweight or obesity and CLBP. Self-reported data were monetised using a bottom-up, prevalence-based approach, and absenteeism and presenteeism were valued via the human capital approach. Mean costs with bootstrapped 95% confidence intervals (CI) were reported in 2025 Swiss Francs (CHF) per cost category. Results: Fifty-three individuals (19 male, 34 female) with a mean age of 47.8 years (SD: 10.1) were included, comprising 18 individuals with overweight and 35 with obesity. Mean direct medical costs were CHF 543.69 (95% CI = [382.80; 686.33]), and mean direct non-medical costs were CHF 19.39 (95% CI = [0.00; 38.63]) respectively. Indirect costs accounted for 80% of total societal costs, with costs attributable to absenteeism of CHF 1,000.39 (95% CI = [2.63; 1,681.40]), presenteeism costs of CHF 549.47 (95% CI = [281.67; 774.67]) and costs due to impaired unpaid work of CHF 745.56 (95% CI = [241.02; 1,436.80]). Total societal costs averaged CHF 2,850.44 (95% CI = [1,667.17; 3,829.17]). Conclusion: Despite the exclusion of individuals with uncontrolled, untreated comorbidities and those receiving invalidity payments, this study demonstrates a substantial financial burden of individuals with overweight or obesity and CLBP. From societal perspective, this burden is primarily driven by productivity losses. These findings emphasise the need for targeted cost-effective clinical interventions, coordinated policy initiatives, and further research to mitigate the significant societal impact of this population. Trial registration number: NCT05811624 (Clinicaltrials.gov). Acronym: BO2WL trial.