Supporting Sustainable Return to Work in Large Organizations: A Cluster Randomised Feasibility Trial of a Multi-Level Intervention

Long-term sickness absence is a growing public health issue, reducing workforce participation and widening health inequalities. Effective interventions must address both health and workplace factors to enable not only return-to-work but sustained employment. This study evaluated the feasibility of a multi-level workplace intervention to support sustainable RTW in large organizations. A two-arm cluster randomised feasibility trial was conducted in nine UK organizations (≥600 employees). Participants included senior leaders and HR professionals (n = 91), workers on long-term sick leave (n = 112), and line managers (n = 83). The IGLOo intervention combined e-learning for leaders/HR with structured toolkits for workers and managers to support RTW before and after return. Feasibility outcomes included recruitment, retention, engagement, acceptability, and usability. Secondary outcomes included RTW timing, sustained participation, mental health, and workplace factors. A mixed methods process evaluation explored implementation and context. Retention, acceptability, and usability met targets, but recruitment and engagement were lower than expected. Potential mechanisms included improved confidence, communication, and self-management. Organizational systems and pressures affected delivery. Exploratory analyses suggested different patterns of return-to-work trajectories across trial arms. Overall, the intervention was acceptable to participants who engaged with it, but recruitment barriers and organizational constraints require substantial modification before any future efficacy trial.