Process evaluation of a problem solving intervention to prevent recurrent sickness absence in workers with common mental disorders

Common mental disorders (CMDs) are a major cause of sickness absence. Twenty to 30% of the workers who return to work after sickness absence due to CMDs experience recurrent sickness absence. We developed the Stimulating Healthy participation And Relapse Prevention (SHARP)-at work intervention, a problem solving intervention delivered by occupational physicians (OPs), to prevent recurrent sickness absence in this worker population in The Netherlands. A process evaluation was conducted alongside a cluster-randomised controlled trial to (1) evaluate whether the SHARP-at work intervention was implemented according to the protocol and differed from treatment in the control group, and (2) to investigate the relationship between the key elements of the intervention and the effect outcome (i.e. recurrent sickness absence). We collected process data for both the intervention and control group on recruitment, reach, dose delivered, dose received, fidelity, context and satisfaction. Data on recurrent sickness absence was collected through the registry system of the collaborating occupational health service. The study was performed in the Netherlands, and between 2010 and 2012, 154 OPs and 158 participants participated. Compared to the control group, participants in the intervention group more frequently had two or more consultations with the OP (odds ratio [OR] = 3.2, 95% confidence interval [CI] = 1.2-8.8) and completed more assignments (OR = 33.8, 95% CI = 10.4-109.5) as recommended in the intervention protocol. OPs and participants were satisfied with the intervention and rated it as applicable. Several individual intervention components were linked to the effect outcome. The process evaluation showed that the SHARP-at work intervention was conducted according to the protocol for the majority of the participants and well-received by OPs and participants. Furthermore, the intervention differed from treatment in the control group. Overall, the results provide support for implementing the intervention in practice.