Cost-effectiveness of a transdiagnostic group exercise intervention for mental health in Germany (ImPuls trial): an economic evaluation study

BACKGROUND: Standard treatments for mental health outpatients have high non-response rates and are often difficult to access. Exercise therapy has shown effectiveness in this population, but evidence on its cost-effectiveness is scarce and mixed across studies. This study aimed to assess the cost-effectiveness of ImPuls, a transdiagnostic group exercise intervention for outpatients with common mental disorders. METHODS: This study was part of the multicentre, randomised controlled trial (n=400) comparing ImPuls plus treatment as usual (TAU) with TAU alone in German outpatient care. Participants (aged 18-65 years) had a diagnosis of moderate or severe depression, primary insomnia, post-traumatic stress disorder, panic disorder, or agoraphobia. ImPuls was a 6-month transdiagnostic group exercise intervention that included supervised group-based aerobic exercise (weeks 0-4) and unsupervised group and exercise activities supported by targeted behavioural and educational strategies, regular therapist calls, and a smartphone application (weeks 5-24). Global symptom severity, which was the primary outcome of the initial trial (measured using the Brief Symptom Inventory [BSI-18]), and health-related quality of life were assessed at baseline, 6 months, and 12 months. Health-care costs were analysed on the basis of statutory health insurance claims data. For the cost-effectiveness analysis, incremental total costs and incremental changes in BSI-18 and quality-adjusted life-years (QALYs) were estimated; QALYs were calculated from EQ-5D-5L utility values. Cost-effectiveness and cost-utility analyses were assessed at 12 months from the statutory health insurance perspective on an intention-to-treat basis, using the incremental cost-effectiveness ratio (ICER) and incremental cost-utility ratio (ICUR). The study is part of the preplanned analysis of the the ImPuls trial (registered with the German Clinical Trials Register as DRKS00024152). People with lived experience were not involved in the study design, conduct, and reporting. FINDINGS: Of the 400 individuals in the ImPuls trial, claims data were available for 389 participants. Mean total health-care costs were €8932 (SD 13 688) in the intervention group and €7168 (9489) in the control group in the 12 months before baseline, and €5556 (7370) in the intervention group and €5683 (SD 7487) in the control group in the 12-month follow-up. There were no significant differences in health-care use or unadjusted costs among the cost categories, with the exception of inpatient hospital costs (€-1324; bootstrapped 95% CI -2504 to -215), and no significant difference in total statutory health insurance costs between ImPuls plus TAU and TAU alone. At 12 months, ImPuls plus TAU achieved better outcomes than TAU alone, with a -3·78-point (95% CI -5·91 to -1·65) greater reduction in BSI-18 scores and a quality-adjusted life-years (QALYs) gain of 0·032 (95% CI 0·005 to 0·058). Including intervention costs, the estimated incremental difference in total costs at 12 months was €553 higher in the intervention group (95% CI -148 to 1255), corresponding to an ICER of €146 per BSI-18 point reduction and an ICUR of €17 543 per QALY. Assuming a willingness-to-pay threshold of €30 000 per QALY in Germany, the probability of ImPuls being cost-effective was 77%. The sensitivity analyses produced similar results. INTERPRETATION: ImPuls shows promise as a cost-effective transdiagnostic group-based exercise intervention for improving mental health in outpatient care when added to TAU. It could be considered for implementation alongside standard outpatient services. FUNDING: Innovation Fund of the German Federal Joint Committee.