Protocol: Evaluating the Effectiveness and Economic Return of a Scaled Workplace Health Intervention – An Incomplete Stepped-Wedge Trial

Background:
Musculoskeletal (MSK) pain is a leading cause of disability and sick leave worldwide, affecting ap-proximately 1.71 billion people globally and accounting for about 149 million years lived with dis-ability annually [1]. In Denmark, MSK pain is the leading cause of general practitioner visits, hospi-tal admissions, and sickness absence, with estimated healthcare costs of 12 billion DKK and productivity losses of 40 billion DKK annually [2]. Childcare workers in Denmark experience a high prevalence of MSK pain, poor mental well-being, and elevated sickness absence, largely due to high physical and psychosocial work demands [3,4].
Between 2018 and 2019, the participatory ergonomic intervention "TOY" demonstrated both fea-sibility and cost-effectiveness, resulting in a 63% return on investment and a significant reduction in pain-related sickness absence among childcare workers in Copenhagen [5,6]. Building on this success, the Child and Youth Administration of Copenhagen has initiated a large-scale rollout of an adapted version of TOY – termed "Copen-SCALE" – to be offered to all 300+ municipal childcare institutions between 2024 and 2027.
Objective:
This study protocol outlines the evaluation of the Copen-SCALE intervention. The primary aim is to assess the intervention’s effectiveness and cost-effectiveness in reducing pain-related sickness absence. Secondary aims include evaluating additional outcomes such as musculoskeletal pain intensity, presenteeism, and occupational health literacy.

Methods:
Copen-SCALE will be evaluated using an incomplete stepped-wedge controlled trial design [7]. The intervention consists of four components: (1) promotion of children's self-reliance, (2) participa-tory ergonomics, (3) pain prevention education, and (4) health-promoting physical activity. All childcare institutions offered the intervention within Copenhagen Municipality are eligible to par-ticipate in the trial. The trial will assess both organizational and individual outcomes, with a pri-mary focus on pain-related sickness absence. Effectiveness will be evaluated through multilevel analyses of register-based and survey-based data. Cost-effectiveness will be assessed from the employer’s perspective using cost-benefit analyses, including estimates of Return on Investment (ROI) and Incremental Cost-Effectiveness Ratios (ICERs) [9].
Discussion:
Copen-SCALE offers a unique opportunity to evaluate the real-world implementation of a previous-ly tested and adapted workplace health intervention at full municipal scale. This research will generate new insights into the process of scaling up ergonomic and health-promotion interven-tions in occupational settings. The findings have the potential to inform occupational health policy and practice across Denmark and beyond, supporting the long-term well-being and retention of childcare workers.
Trial registration: ISRCTN registry (ISRCTN14831585)