Objectives The aim of this study was to evaluate the effect of the Danish return-to-work (RTW) program on long-term sickness absence in a randomized controlled trial in three municipalities.

Methods The intervention group comprised 1948 participants while the control group comprised 1157 participant receiving ordinary sickness benefit management (OSM). Study participants were working-age adults receiving long-term (≥8 weeks or more) benefits, included regardless of reason for sickness absence or employment status. Each beneficiary was followed-up for a maximum period of 52 weeks. Cox proportional hazards model was used to estimate hazard ratios (HR) for return to work (RTW) with 95% confidence intervals (95% CI).

Results The intervention effect differed significantly between the municipalities (P=0.00005). In one municipality (M2) the intervention resulted in a statistically significant increased rate of recovery from long-term sickness absence (HR 1.51, 95% CI 1.31–1.74). In the other two municipalities, the intervention did not show a statistically significant effect (HR_M1 1.12, 95% CI 0.97–1.29, and HR_M3 0.80, 95% CI 0.63–1.03, respectively). Adjustment for a series of possible confounders only marginally altered the estimated HR.

Conclusion The effect of the intervention differed substantially between the three municipalities, indicating that that contextual factors are of major importance for success or failure of this complex intervention.

Key terms coordinated case management; Denmark; effect evaluation; intervention; long-term sickness absence; multidisciplinary; randomized controlled trial; return to work; return-to-work program; sickness absence; work resumption