Late-life depression is a highly prevalent disorder that causes a large economic burden. A stepped collaborative care program was set up in order to improve care for patients with late-life depression in primary care in Germany: GermanIMPACT is the adaption of the Improving Mood-Promoting Access to Collaborative Treatment (IMPACT) program that has already been established in primary care in the USA. The aim of this study was to determine the cost-effectiveness of GermanIMPACT compared with treatment as usual from a societal perspective.

This study is part of a 12-month bi-centric cluster-randomized controlled trial aiming to assess the effectiveness of GermanIMPACT compared with treatment as usual among patients with late-life depression. A cost-effectiveness analysis using depression-free days (DFDs) was performed. Net-monetary benefit (NMB) regressions adjusted for baseline differences for different willingness-to-pay (WTP) thresholds were conducted and cost-effectiveness acceptability curves were constructed.

In total, n = 246 patients (intervention group: n = 139; control group: n = 107) with a mean age of 71 from 71 primary care practices were included in the analysis. After 12 months, adjusted mean differences in costs and DFDs between intervention group and control group were +€354 and +21.4, respectively. Only the difference in DFDs was significant (p = 0.022). According to the unadjusted incremental cost-effectiveness ratio, GermanIMPACT was dominant compared with treatment as usual. The probability of GermanIMPACT being cost-effective was 80%, 90% or 95% if societal WTP per DFD was ≥€70, ≥€110 or ≥€180, respectively.

Evidence for cost-effectiveness of GermanIMPACT relative to treatment as usual is not clear. Only if societal WTP was ≥€180 for an additional DFD, GermanIMPACT could be considered cost-effective with certainty.