The main findings in this study showed that 44% of the eligible workplaces adopted the intervention. These workplaces had a more stable organization as well as a management with more positive beliefs of the intervention’s potential benefits. The reach was 71% for the questionnaire responders group and the reach for employees consenting to participate was 57%. Non-responders and non-consenters did not differ from the responders and consenters, respectively, on age, sex, and job group. More responders had high seniority, were working day shift, were working more than 30 hours pr. week, and were higher skilled compared to non-responders. The consenters and non-consenters showed no differences in BMI, smoking and leisure time physical activity, but consenters had more pain and reduced health, as well as higher physical exertion during work compared to non-consenters.
The 44 percent adopters in the present study is slightly lower than in other trials which have reported on adoption of health promoting initiatives in the workplace, and finding that 50-58% of the workplaces adopted the initiatives [22, 23]. The municipality was granted financial aid to cover some of the expenses regarding implementation of the project but still some of the districts declined to participate. It therefore seems that the money was not a main incentive for participating.
In addition to investigating the percentage of adopters, we also investigated potential differences between adopters and non-adopters. For all 9 districts there is a policy regarding patient transfer techniques with mandatory courses for all new employees as well as brush-up courses every second year. When asking about additional projects nearly all districts (8 out of 9) had more than 2 ongoing projects. One of the non-adopting districts had no ongoing projects. The projects primarily focused on the psychosocial working environment and management development and to a lesser degree health promotion. However, none of the adopting districts had ongoing projects concerning the physical working environment whereas more than half of the non-adopting districts had ongoing projects concerning the physical working environment. This lack of existing projects on this particular topic in the adopting districts may explain the adoption of the present project focusing on the physical working environment to reduce LBP.
We found that the working environment reported by the managers was relatively similar between adopters and non-adopters, whereas there were differences in the management and organizational stability. The overall differences in management were primarily related to the managers’ assessment of the project requirements (time and expenses), with the managers of the non-adopting districts assessing them to be higher than the adopting districts. Also the managers of the non-adopting districts did not believe that the intervention would be beneficial in terms of solving their needs and reducing the sickness absence, increase wellbeing at work, or increase quality in work. Moreover, it was shown that non-adopters had a more unstable organization with more reporting abatement, staff reduction and turnover rate than the adopting districts. Their management was more recently replaced and they predicted that there would be organizational changes during the study period to a higher degree compared to the adopting districts. The reasons among non-adopters for not adopting the project were mostly related to the organizational stability as many of them had experienced or anticipated restructurings within the near future. These findings indicate that workplaces are more reluctant to adopt an initiative, if the organization is not stable. This corresponds well with the findings by Jørgensen et al. 2010  reporting that cleaning workplaces facing organizational changes did not adopt the project. Moreover, the differences between the management among adopters and non-adopters indicate that management beliefs about the benefits of the project are important for adoption of the intervention. This is in accordance with previous studies . Often it rests in the hands of a few individuals, usually senior managers, to decide whether or not a workplace will adopt a workplace program . However, in this study all the managers of the adopting districts had involved employees in the decision regarding participation in contrast to the non-adopting districts. This may imply either that when a manager is convinced about the projects benefits, they are more likely to involve the employees in further decisions or that employee involvement increases the odds of adopting the initiative. In support of our findings on the importance of employee involvement Witte 1993  reported that organizations with democratic management were more likely to adopt health promotions programs. However, we do not know whether employee involvement happened before or after the managers’ initial decision about participation. Future research is needed to more systematically examine these management factors and employee involvement and discover how they are linked to adoption of workplace health promotion programs.
Reach of responders
In this study, 71% of the eligible population participated in an information meeting about the project (responders). Among the responders, most of them (80%) chose to participate, and thus information meetings seem to be an important recruitment tool. However, nearly 30% of the eligible employees did never attend an information meeting (non-responders). Particularly in one district (district 4), attendance at information meetings was lower compared to the other districts. District 4 was the smallest district with 134 eligible employees compared to up to 352 eligible employees in the other districts. Even though this district had fewer eligible employees, the relative reach of responders was lower. In this district, we offered fewer information meetings than in the other districts (4 compared to up to 21) due to a district management decision. Thus maybe higher accessibility of information meetings is important for the reach of participants as it has been suggested in a previous study . Particularly some groups attended the information meetings less: evening and night shift workers (OR = 3.11), workers working 30 hours pr. week or less (OR = 4.15), newly employed workers (OR = 1.70-2.32) and workers with lower skill levels (OR = 4.15). Even though we had information meetings at all times of the day, many of the non-responders were employees working evening or night shift. Shift work has been suggested as a cause of unequal access to health promotion . Therefore it seems that special initiatives are needed for reaching the group of employees working evening or night shift. The lower amount of responders working 30 hours or less pr. week is in accordance with previous studies showing that full-time workers are more likely to participate [5, 27]. Among non-responders there was also a higher rate of newly employed workers. According to the authors’ knowledge, no studies on reach in worksite health promotion have focused on this aspect of newly employed workers. It has been suggested that for newly employed workers, the managers should be especially aware of their socialization process at the workplace  which may be of particular importance with respect to reach of newly employed workers in health promotion initiatives.
Reach of consenters
Fifty-seven percent of the eligible employees consented to participate in the intervention. Reach corresponds well with previous studies, although there are large discrepancies ranging from 33% to 61% [5, 9]. Robroek and colleagues  concluded that multiple component programs generally had higher participation rates, probably causing better reach to the target group. The multi-faceted intervention offered in the current study can therefore possibly explain the relatively high reach rate.
Among the consenters and non-consenters there were no differences in age, sex or health parameters such as BMI, smoking and leisure time physical activity. Other studies show contradicting results with respect to demographic factors such as age and sex between consenters and non-consenters . Also for health-related determinants, there is no consistent evidence for a higher participation among healthier employees . For example, studies have shown that obese employees are more likely to participate in workplace health promotion [5, 22]. Equivalent to the reach of responders, workers working 30 hours or less pr. week to a higher degree did not consent to participate (OR = 2.02). Also working evening/nightshift increased the OR for non-consenting (OR = 2.05).
The multi-faceted intervention was designed to prevent and reduce LBP and consequences of LBP among nurses’ aides in elderly care in Denmark. This study shows that consenters had more pain and reduced self-rated health compared to non-consenters. This indicates that the study appealed to an unhealthier proportion of the nurses’ aides, which is consistent with the findings of a study by Jørgensen et al. 2010 on cleaners . We also found that the consenters reported a higher physical exertion during work. In the current study, the intervention focused on preventing and reducing LBP, which included, among other things, a focus on reduction of physical exertion during work. This may explain why employees experiencing high physical exertion during work were actually motivated to enroll in the study. The reach of employees with health-issues in this study is highly relevant for the workplace health promotion and work environment intervention aiming at reducing LBP. However, since this is a job group with high prevalence of LBP [29, 30] a high reach of healthy employees is less likely to occur. In a preventative perspective, reach of the smaller proportion of healthy employees is also relevant, but it may require a different recruitment strategy.
Like non-responders, non-consenters were more likely to work evening or night shift and have lower skill levels. When investigating reasons for not participating, 11% of the evening/night shift workers answered lack of time, whereas for day shift workers the number was 3% to the same question. However, reasons for the lower reach of evening and night shift workers as well as lower skilled workers need future studies, to understand why certain groups choose to participate less. Furthermore, future workplace initiatives should pay attention to this issue, since particularly high risk groups may miss out on important health promotion opportunities.
Nearly all the consenters (98%) found the project relevant in comparison to 83% of the non-consenters. However, the odds for not consenting to participate were more than 8 for those finding the project not relevant compared to those finding the project relevant. The high percentage of the non-consenters still finding the project relevant points towards other reasons for not participating. The non-consenters, when asked about the reasons for not consenting to participate, answered: lack of time, not wanting the workplace to interfere with health, not knowing what the project is about, and not finding the project interesting. A study by Robroek and colleagues  on moral issues in workplace health promotion shows similar results: The main reasons for non-participation was lack of time and not wanting the workplace to interfere with health. We would have assumed that the reason lack of time was absent in the current study, since participation was offered during paid working hours.
The recruitment process of both workplaces and employees of this study provides knowledge of the representativeness of the population, and consequently the external validity and the generalizability of the results of the intervention study. Using the RE-AIM framework’s two measures, reach and adoption, we gain important insights on the representativeness of the study, which may improve the ability of practitioners, workplaces and researchers to successfully plan and implement future workplace health promotion and work environment interventions.
Strengths and limitations
The focus on both the individual and the organizational level is a strength of the study. Another strength of the study is the collection of data on adopters and non-adopters, so that we can report on characteristics and not just the percentage of adopters. Our measure of reach on both responders and concenters level, is a strength as it besides information about those who actually did participate in the intervention also provides knowledge of the absolute number, proportion, and representativeness of individuals who are willing to participate in a given intervention. Moreover the large amount and relevance of information available for comparing responders and non-responders as well as consenters and non-consenters offers an opportunity to investigate the feasibility and external validity of the intervention and intervention effects.
A limitation of the study is that only one municipality was represented in this study, meaning that this sample of nurses’ aides is not a representative sample of nurses’ aides in Denmark. Furthermore, this time-consuming intervention was provided to the employees with a low monetary cost to the workplace (as they were granted money for the implementation of the intervention). Thus, we are unable to predict participation in future similar workplace interventions in which a greater investment of resources is required from the workplace.