**1. Introduction**

A number of chronic diseases are known to be associated with psychosocial work stressors, especially low job control, and other organizational factors such as night shift and overtime work [1–5]. It can be argued that because psychosocial job strain is an important predictor of health behaviors, a workplace health promotion (HP) program should seek to improve stressful working conditions in order to support healthy behaviors. Workplace HP programs have traditionally focused instead on trying to modify individual behaviors that increase disease risk. Workplace HP benefits are often unevenly distributed by worker socioeconomic status [6–8]. This may be, at least in part, because low-wage, low-status workers face more conditions at work which are obstacles both to the same health behaviors that are HP targets [8–10] and to HP participation [11].

A newer approach to workplace HP is that of enhancing its effectiveness by combining it with occupational safety and health (OSH) protections. This concept of integrated employee health programs has been put forward by a few researchers [12,13], the World Health Organization [14], and the U.S. National Institute of Occupational Safety and Health [15]. An integrated strategy has been evaluated empirically by some investigators [16–18] but evidence is still sparse as to its effectiveness [19], in part because implementation approaches differ among investigators and thus are hard to compare [20]. Meanwhile, the norm in most workplaces is still that safety programs and workplace HP programs are managed separately.

Healthcare work is physically and psychologically demanding, exposing workers to many workplace stressors that affect their safety and health and which simultaneously may interfere with effective prevention measures [21–23]. We designed an intervention for the long-term healthcare sector based on a participatory model that engaged employees in examining and improving the physical, organizational, and psychosocial conditions at work that might impact their health and well-being. The program sought to bridge and integrate occupational safety and health with health promotion by identifying higher-level determinants of employee health and safety [24].

We have previously proposed [9,25] that any workplace health program should involve the workers in a decision-making role, both to ensure that obstacles to workers' healthy behaviors are recognized and addressed and to increase workers' decision latitude, a well-known and key health determinant. In a participatory approach, employees are actively engaged in problem identification, program design, implementation and evaluation of the program. The direct involvement of workers in the planning and design of interventions can benefit group and individual self-efficacy, which is consistent with the concept of "sense of coherence" [26], an internal resource for overcoming stress, reducing burnout and other adverse outcomes [27,28]. Participatory ergonomics is one example with demonstrated success as a way to reduce hazardous conditions in the workplace [29,30]. As discussed in depth by Jagosh et al. [31], "partnership synergy" provides a theoretical basis for assessing the links among participatory intervention context, mechanism(s), and outcomes (with elements also commonly utilized in process evaluations).

This article reports our evaluation of process fidelity, extent of OSH/HP integration, health impact, and sustainability of the participatory intervention program. In line with the middle-range "partnership synergy" theory, we have relied on information collected before, during, and after the study to describe the context (institutions and workforce), evidence for posited mechanism of change (e.g., fidelity and amount of intervention), and short- and medium-term outcomes (institutional and individual). The intervention was compared three to four years after initiation in the three participatory intervention program (PIP) sites to three control sites with non-participatory health promotion (NPHP) programs.
