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Abstract
Objectives To study the effect of a participatory ergonomics intervention on psychosocial factors among kitchen workers.
Design A cluster randomised controlled trial.
Setting Four cities in Finland, 2002–2005.
Participants 504 workers in 119 municipal kitchens.
Intervention Kitchens were randomised to intervention (n=59) and control (n=60) groups. The intervention lasted 11–14 months and was based on the workers' active participation in work analysis, planning and implementing the ergonomic changes aimed at decreasing the physical and mental workload.
Main outcome measures Mental stress, mental strenuousness of work, hurry, job satisfaction, job control, skill discretion, co-worker relationships and supervisor support. Data were collected by questionnaire at baseline, at the end of the intervention, and at a 12-month follow-up (PI12).
Results At the end of the intervention, the OR of job dissatisfaction for the intervention group as compared with the control group was 3.0 (95% CI 1.1 to 8.5), of mental stress 2.3 (1.2 to 4.7) and of poor co-worker relationships 2.3 (1.0 to 5.2). At the PI12, the OR of job dissatisfaction was 3.0 (1.2 to 7.8). Analysis of the independent and joint effects of the intervention and unconnected organisational reforms showed that adverse changes were accentuated among those with exposure to both.
Conclusions No favourable effects on psychosocial factors at work were found. The adverse changes were due to a joint effect of the intervention and the unconnected organisational reforms. The findings do not support the usefulness of this kind of intervention in changing unsatisfactory psychosocial working conditions.
- Psychosocial factors
- intervention
- ergonomics
- organisational reform
- kitchen work
- cluster randomised controlled trial
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- Psychosocial factors
- intervention
- ergonomics
- organisational reform
- kitchen work
- cluster randomised controlled trial
Introduction
Participatory ergonomics is recommended to reduce musculoskeletal disorders (MSDs)1–5 and its potential as an effective means to improve unsatisfactory psychosocial work factors has been emphasised.6–11 Evidence on the effectiveness of this approach is sparse.6,12–14 We carried out a cluster randomised controlled trial in the kitchens of the municipal food services of four large cities in Finland.15
Our target group was a challenging one. In Finland, kitchen work is one of the municipal occupations where workers have reported high physical work strain and fast work pace, unsatisfactory working climate, low correspondence between knowhow and work, need for education, fear of temporary dismissals or notices, much self-reported sickness absences and poor perceived health.16 Disability pension incidence is also high.17
We hypothesised that optimisation of the mental and biomechanical load at work would prevent MSDs, in accordance with the aetiological model of Sauter and Swanson.18 Several psychosocial factors have been associated with the occurrence of MSDs: rapid work pace, monotonous work, low job satisfaction, job stress and non-work-related stress, high job demands, little control at work, and low workplace social support.13 19–22
A participatory intervention consists of workers' involvement and active participation in problem-solving, planning and implementation of the development of their own work processes supported by supervisors and management.7 23–26 Few studies have examined the effect of workplace interventions on psychosocial factors at work13 or psychosocial factors as intermediate variables in the evaluation of the effectiveness of participatory ergonomics interventions on health outcomes.1 We assumed that group work during the intervention would have a positive effect on the psychosocial environment in the intervention kitchens.
A previous report by our research group showed no evidence for the efficacy of the intervention in preventing MSDs.15 To interpret the result, it is essential to examine the changes in the intermediate variables. The intervention showed no positive effect on perceived physical workload, while changes in some psychosocial factors seemed to be negative, especially in the intervention group.15
In this paper, our aim was to comprehensively report on the effects of the intervention on psychosocial factors at work and on mental stress. As a secondary analysis, we examined the independent and joint effects of the intervention and organisational reforms, unconnected with the intervention, which were planned and implemented in two of the four cities' food services during the study.
Methods
Study design
This report is one of a series on a cluster randomised controlled trial regarding the efficacy of a participatory ergonomics intervention in preventing MSDs.15 27 Altogether 119 municipal kitchens (60% of the eligible kitchens) of schools, kindergartens and nursing homes in four large cities in Finland were randomised to the intervention (n=59) or control (n=60) group. The total number of workers was 504 (487 women, 17 men). The Ethics Committee of the Finnish Institute of Occupational Health approved the study proposal. A research agreement was signed with each city and a written informed consent was obtained from each kitchen and each worker.15
The study started at the beginning of 2002. For feasibility reasons, the intervention and control kitchens were divided into 16 series each containing eight kitchens (four intervention and four control kitchens) on average. The series entered the active study phase sequentially in time, that is, within each series the kitchens of both study arms proceeded in parallel. All 16 kitchen series completed the intervention process which was run by four teams of two researchers each. Each series had a 12-month post intervention follow-up. The intervention phase of the study as a whole was completed by the end of 2004 and the follow-up by the end of 2005.15
Unconnected organisational reforms
In two of the participating cities, a major organisational reform of food services took place during the study. Altogether 62 kitchens (31 intervention and 31 control kitchens) were involved in these reforms. In one city, the planning and implementation of the reform was carried out simultaneously with our intervention. In the other city, the reform was planned during the intervention and began during the 12-month follow-up. The most important change was that cooking was centralised to large production kitchens, from which meals were delivered to other kitchens to be distributed to the clients. Also, plans for the outsourcing of the food services or organising the services as a public utility were discussed.
Randomisation and sample size
Randomisation was carried out by a researcher not involved in the field study and using an assignment algorithm (ARD, alternate ranks design)28 and stratification by area (city district) and type of kitchen (school, kindergarten, home for senior citizens, other institution).15 Based on power calculations and assumptions (intraclass correlation 0.50, α 0.05, power 0.80, 15% difference between the compared groups, and average of three subjects per kitchen) the number of kitchens needed was 80 per arm. At baseline, however, the empirical intraclass correlations for psychosocial factors varied between 0.0 and 0.29. Therefore, the final number of kitchens was sufficient to have the assumed statistical power. Intraclass correlations for workers in the same city area varied from 0.0 to 0.06.
Table 1 shows the success of the randomisation by comparing the baseline characteristics among the intervention and control kitchens.
Baseline information given at cluster and individual level
Participatory ergonomics intervention
Details on the content and evaluation of the intervention process and results of its efficacy in preventing MSDs have been previously reported.15 27 In brief, the framework of the intervention was based on the model developed at the Finnish Institute of Occupational Health.29 The active role of workers in collaboration with technical staff and management was emphasised. The researchers acted as consultants and trainers and facilitated the progress of the intervention process. The intervention comprised a 2-month pre-implementation and 9–12-month implementation phase promoted by eight workshops (total 28 h). Due to summer holidays at schools, the total duration of the intervention varied from 11 to 14 months.
During the pre-implementation phase, the intervention kitchens' personnel in each series participated in two 5 h workshops. In the first workshop, the workers were taught the basic principles of ergonomics and about the functioning of the musculoskeletal system. They were trained and encouraged to analyse their work tasks and processes in order to recognise strenuous tasks and risk factors for MSDs and to seek solutions to decrease physical and mental workload. Before the second workshop, the workers had 1 month to analyse their work and develop ideas to improve ergonomics. The researcher gave support by visiting and phoning each kitchen once. In the second workshop, every kitchen decided on their primary targets and planned the execution of the intervention.
During the implementation phase, six 3 h workshops were arranged for all workers of the intervention kitchens in each series. Each workshop included a specific theme related to ergonomics (working postures, manual materials handling, repetitive work, hurry, physical risk factors and work safety) and the progress in each kitchen was discussed. The average participation rate in the workshops was 73% (66% in the cities with no organisational reforms and 81% in the cities with reforms). Within each series, the workshops rotated from one kitchen to another to give the workers an opportunity to learn from each other's solutions and practices. The researcher made extra visits on request. Food service managers and technical staff were invited to participate in the workshops. A local steering group was established in two cities to improve the exchange of information. The control kitchens continued their normal activity and no training by the researchers was provided for them.
Data collection, worker turnover and loss to follow-up
Baseline data on sociodemographic and lifestyle factors, morbidity, employment history and perceived physical workload were collected before randomisation. Information on individual level psychosocial factors was gathered by a questionnaire at baseline, at the end of intervention (post intervention assessment, PIA) and at the 12-month post intervention follow-up (PI12). A researcher distributed the questionnaires to all participating kitchens in both study arms. Information on spontaneous ergonomic changes in the control kitchens was collected by short interview during these visits. If a worker was on sick leave or vacation, the questionnaire was mailed to her/his home address or she/he was asked to respond within 1 week of returning to work. Non-respondents were reminded by telephone after 2 weeks. Response rates were 99% at baseline, 95% at the end of the intervention, and 92% at the 12-month follow-up.
Five kitchen series finished the intervention phase at 9 months (n=157) and 11 series at 12 months (n=295). The post-intervention assessment (PIA) was thus made at either at 9 or 12 months after the start of the implementation phase (combined n=452). The number of respondents in different surveys is shown in table 2.
Number of participants in the study arms at baseline (BL), at the end of the intervention (post intervention assessment, PIA) and at 12-month follow-up (PI12) according to occurrence of organisational reforms
Throughout the intervention, 86% of the intervention and 84% of the control kitchen workers stayed employed in the same kitchen. For the 12-month follow-up, the rates were 70% and 71%, respectively.
Definition of outcome variables and covariates
Outcome variables
Psychosocial factors were assessed using adapted questions from a validated questionnaire.30 All items initially had five categories and were dichotomised as shown below.
Mental stress during the past month
“Stress means a situation in which a person feels tense, restless, nervous or anxious or is unable to sleep at night because his/her mind is troubled all the time. Have you felt like this during the past month?” 1=not at all, 2=only a little, 3=to some extent, 4=quite a lot, 5=very much. Dichotomised as no (1–3)/yes (4–5).
Mental strenuousness of work
“Is your work mentally strenuous?” 1=not at all, 2=rather light, 3=somewhat strenuous, 4=rather strenuous, 5=very strenuous. Dichotomised as no (1–3)/yes (4–5).
Hurry at work
“Do you have to hurry to get your work done?” 1=never, 2=seldom, 3=now and then, 4=often, 5=constantly. Dichotomised as no (1–3)/yes (4–5).
Job dissatisfaction
“How satisfied are you with your present work?” 1=very satisfied, 2=rather satisfied, 3=neither satisfied nor dissatisfied, 4=rather dissatisfied, 5=very dissatisfied. Dichotomised as no (1–3)/yes (4–5).
Low job control
“At work, can you influence matters concerning you?” 1=a lot, 2=quite a lot, 3=to some extent, 4=very little, 5=not at all. Dichotomised as no (1–3)/yes (4–5).
Low skill discretion
“Can you use your knowledge and skills in your work?” 1=a lot, 2=quite a lot, 3=to some extent, 4=very little, 5=not at all. Dichotomised as no (1–3)/yes (4–5).
Poor co-worker relationships
“How do workmates get along at your workplace?” 1=very well, 2=rather well, 3=neither well nor badly, 4=there are some problems, 5=badly. Dichotomised as no (1–3)/yes (4–5).
Low supervisor support
“Does your supervisor provide support and help when needed”? 1=a lot, 2=rather much, 3=to some extent, 4=very little, 5=not at all. Dichotomised as no (1–3)/yes (4–5).
The baseline level of each outcome was coded as follows in the analyses: 0=no (categories 1–3), 1=yes (categories 4 and 5) and 2=missing observations.
Covariates
Musculoskeletal pain index
The occurrence of musculoskeletal pain (no/yes) during the past 3 months in seven anatomical sites (neck, shoulders, forearms/hands, low back, hips, knees and ankles/feet) was queried. A sum index was calculated (0=no pain, …, 7=pain in seven sites).
Physical workload index
The perceived strenuousness of seven different work tasks was queried and coded from 1 (not at all) to 7 (very strenuous).15 The mean was used in the analyses.
Statistical analysis
The results were based on cross-sectional data of the open population31 at baseline, at the end of the intervention (post intervention assessment, PIA) and at the 12-month follow-up (PI12). Each outcome was analysed separately.
Effect of the intervention on psychosocial factors at work
Data were analysed according to the intention-to-treat principle. Three kitchens dropped out right after randomisation15 and were not included in the analyses because only baseline data were available. The study arms were compared using logistic regression models, which take into account the hierarchical structure of the data (the generalised estimating equations approach). The series and individual kitchens were used as subject effects in the models to account for the within-subject correlation. In the first logistic regression model, we included the baseline level of the outcome as a covariate. In the second model, the baseline level of the outcome, age, the musculoskeletal pain index, physical workload index and city were included as covariates.
Independent and joint effects of the intervention and organisational reforms
The independent and joint effects of the intervention and the unconnected organisational reforms on psychosocial factors were assessed. The following coding was used: 1=no intervention, no organisational reform; 2=intervention, no organisational reform; 3=no intervention, organisational reform; 4=intervention, organisational reform. Again, the logistic regression models were first adjusted only for the baseline level of the outcome variable, and the second models also for age, musculoskeletal pain and perceived physical workload.
As the measure of effect, odds ratios (OR) with their 95% CIs were estimated. Two-sided tests of statistical significance (p<0.05) were used. All analyses were performed using SAS v 9.1 and SPSS v 12.0.1.
Results
Effect of the intervention on psychosocial factors
Crude prevalence rates of psychosocial factors at work at the different time-points are illustrated in figure 1. Some of the outcomes developed negatively in the intervention group as compared with the control group (table 3). At the end of the intervention (PIA), the OR of job dissatisfaction was 3.02 (95% CI 1.08 to 8.45), mental stress 2.31 (1.15 to 4.66) and poor co-worker relationships 2.29 (1.00 to 5.22), after adjustment for the baseline level of the outcome. At the 12-month follow-up (PI12), the OR of job dissatisfaction was 3.03 (1.18 to 7.82). After adjustment for all covariates, the association of the intervention with poor co-worker relationships and job dissatisfaction at PIA retained statistically significance. At PI12, low skill discretion also emerged as statistically significantly poorer in the intervention group.
Crude prevalence rates of psychosocial factors among kitchen workers according to organisational reform (Org −, no organisational reform; Org +, organisational reform). The rates are based on cross-sectional data of the open population. Comparison between the intervention and control groups at baseline (BL), at the end of the intervention (post intervention assessment, PIA) and at the 12-month follow-up (PI12). *Some of the kitchens finished the intervention at 9 months and some at 12 months.
Effect of the intervention on psychosocial factors at work among kitchen workers
Independent and joint effects of the intervention and organisational reforms
Figure 1 indicates that there was interaction between our experimental intervention and the organisational reforms unconnected with the intervention, in relation to the psychosocial factors. The independent and joint effects are presented in table 4. No statistically significant independent effects of either the intervention or the unconnected organisational reforms were detected at PIA or PI12. At PIA, a distinct adverse joint effect of the intervention and organisational reforms was observed on mental stress, mental strenuousness of work, job dissatisfaction, low job control and poor co-worker relationships. At PI12, a similar joint effect was found on mental strenuousness of work, hurry, low skill discretion, poor co-worker relationships, and low supervisor support. With one exception (poor co-worker relationships), these adverse joint effects persisted when all covariates were considered.
Independent and joint effects of intervention and organisational reforms on psychosocial factors among kitchen workers
Discussion
We evaluated the effect of a participatory ergonomics intervention, and the joint effect of the intervention and organisational reforms, unconnected with the intervention, on psychosocial factors in kitchen work. The intervention did not have the hypothesised favourable impact on the psychosocial factors. On the contrary, deterioration was observed in several of the employees' reports on psychosocial factors at work and statistically significant differences between the intervention and control group were seen in mental stress, job satisfaction and co-worker relationships at the post intervention assessment, when allowing for the baseline level of the measure. The effect on job satisfaction persisted even at the 12-month post intervention follow-up.
The adverse development in psychosocial factors seemed to be accentuated by organisational reforms that were carried out in the food service of two of the four studied cities concomitantly with our intervention. An unfavourable joint effect of the intervention and the organisational reforms at the post intervention assessment was seen not only on those factors where the overall intervention effect was negative (mental stress, job satisfaction and co-worker relationships), but also on job control and, when adjusted for multiple covariates, on mental strenuousness of work. By the 12-month post intervention follow-up, an unfavourable joint effect was also seen on hurry, skill discretion and supervisor support, when all covariates were considered. The deterioration in the mental strenuousness of work and supervisor support, particularly, worsened after the end of the intervention in the intervention kitchens additionally exposed to organisational reforms.
Few high-quality studies have evaluated the efficacy of interventions – at the individual or organisational level, or using the participatory approach – aimed at reducing psychosocial load at work. Evidence is mostly derived from case studies, while randomised or non-randomised controlled trials are sparse.6 8 12 13 32 The variety in study designs, outcome measures and intervention programs complicates the comparison of the effects on the psychosocial factors. We found no studies comparable to ours, which seems to be the first large cluster randomised controlled trial in this field.
According to a recent review1 concerning the effectiveness of participatory ergonomics interventions on health outcomes, psychosocial variables were considered as risk factors or intermediate outcomes in three studies.9–11 Favourable effects were reported on co-operation among personnel, psychosocial support and solidarity in an engineering plant10 and on job satisfaction, perceived psychosocial stressors, and social support among hospital orderlies.9 In a randomised controlled study in the aluminium industry,11 social support and use of coping strategies pertaining to musculoskeletal symptoms increased in the intervention group of “operators without a supervisor”. Laing et al 33 34 had aims quite similar to those of our study. While they found few systematic changes in mechanical exposures, perceived effort or pain severity,33 communication dynamics regarding ergonomics were enhanced. Still, no differences in decision latitude or influence over work were observed as compared with the referent plant.34
Our intervention of about 1 year's duration was intensive with eight workshops (total 28 h). Due to the characteristics of the participatory approach, positive impacts on psychosocial factors at work were expected.8 According to an evaluation of the intervention process and focus group interviews in two of the cities,27 the workers indicated that the intervention had facilitated discussion among and asking for help from co-workers, the feeling of togetherness within their own kitchen had improved, and the rotation of the workshops in different kitchens was beneficial in enabling learning from each other's good practices.
A participatory process can have negative effects on psychosocial aspects at work if the process causes extra work.8 Regardless of its burden, our intervention was well accepted by both workers and management. Participation in the workshops was excellent and all the kitchens completed the intervention, signifying good commitment to the study. We emphasised active group work and the direct participation of workers in the role of main actors and the best experts in their own work. Although the workers were dissatisfied with support from management and collaboration between kitchens, especially in one of the cities with organisational reforms, the model and the participatory approach as such were found feasible and perceived as motivating.27
However, the effects of the intervention on the psychosocial work environment were unfavourable and accentuated in the kitchens with concomitant organisational food service reforms. In some previous studies,35 36 interventions aimed at the redesign of work had an adverse influence on psychosocial working conditions. Unexpected organisational reforms have been shown to interfere negatively with interventions.37 38 It is common that long-lasting intervention studies may be confronted by unplanned changes beyond the control of researchers 6 39 40 as happened to us. It may be that the workers were disappointed in their expectations that the intervention would improve unsatisfactory working conditions under the pressure of the organisational reform. Indeed, the workers' expectations regarding the effects of the intervention were higher before the intervention than after it.27 Participation in the intervention simultaneously with the implementation of the reform may have been overly straining for the workers. Participation in the workshops was more active in the cities with than in those without reforms, possibly increasing the overload of the workers in the middle of tightened work demands.
Centralising food preparation to certain kitchens increased during the reforms and increased the number of kitchens where food was only distributed to the clients. Probably work tasks became more monotonous in the latter kitchens and workers' ability to use their skills diminished. A threat of restructuring the food service as a public utility or outsourcing the functions may have increased the employees' fear of job loss causing uncertainty and extra tension and competition between the workers.
Our study design guaranteed good comparability between the groups despite the major unconnected reforms. Within each series, the kitchens of both study arms proceeded in parallel. Randomisation seemed to be successful and stratification by area and type of kitchen ensured balanced clusters with respect to the baseline characteristics. In both groups, about 70% of the baseline population was employed in the same kitchen throughout the study. Despite the staff turnover, the groups remained similar throughout the intervention phase with regard to assessed potential confounders. Baseline data were collection was made blinded to the group status and the researchers had no access to the data during the data collection. Quality control based on regular meetings was applied to ensure similarity of working methods between the researcher teams in different cities. In addition, a project coordinator participated in the workshops and observed the working of researchers and provided them with feedback.
The strengths of our study include the relatively large sample size and sufficient power, a homogenous occupational and gender structure, good compliance, very high response rates, and the inclusion of a 1-year follow-up survey after the completion of the intervention phase. Due to financial and time constraints we had to limit the follow-up period to 1 year. However, an even longer follow-up would have been desirable to enable examination of the persistence of the adverse changes.
Because our intervention was targeted to the community (ie, kitchen) level, we used repeated cross-sectional analyses of the open population at three time points. This approach has been recommended as more appropriate than longitudinal analyses for measuring the effectiveness of interventions in the community. Disadvantages of this approach may be that analyses possibly include workers who received limited exposure to the intervention or that intervention diffuses across other communities.31 In this study, at least 70% of the workers stayed employed in the same kitchen throughout the study period. If the workers changed kitchen, they were asked not to talk about the study process. Only two workers were transferred from an intervention kitchen to a control kitchen during the intervention, indicating that contamination was probably minor.15
This study was a part of a research programme aimed at studying the efficacy of a participatory ergonomics intervention in the prevention of MSDs.15 Psychosocial factors are known to be associated with MSDs and, thus, were considered as intermediate outcomes. We found no favourable effects on mental stress or work-related psychosocial factors. Instead, a deterioration in several of the employees' reports on these measures was observed. This may partly explain why the intervention did not have an effect on the occurrence of musculoskeletal symptoms or sick leaves. The adverse overall effects were mainly due to a joint effect of the intervention and unconnected major organisational reforms of food service in two of the participating cities. The adverse joint effect of the intervention and organisational reforms was seen for the majority of the eight measured psychosocial work factors. Because no evidence for efficacy of the intervention was found in improving psychosocial working conditions, reducing perceived physical workload or preventing MSDs,15 there seems to be a need to re-consider the usefulness of this approach. It also seems that if organisational reforms are known to occur, the implementation of a simultaneous workplace intervention should proceed with caution. A similar study under different work circumstances, as well as among men, is needed, before final conclusions on the utility of the approach can be drawn.
What this paper adds
There is little evidence on the effects of workplace interventions on psychosocial factors at work or psychosocial factors as intermediate outcomes in the evaluation of the efficacy of workplace interventions on health outcomes.
The current cluster randomised controlled trial conducted among municipal kitchen workers showed, contrary to our hypothesis, unfavourable effects of the participatory ergonomics intervention on mental stress and psychosocial factors at work as intermediate outcomes; this may partly explain why the intervention did not have an effect on the primary outcome, the occurrence of musculoskeletal disorders.
Deterioration in the majority of the psychosocial variables was observed; the adverse effects were mainly due to a joint effect of the intervention and unconnected organisational reforms of food service in two of the participating cities.
The findings do not support the usefulness of this kind of participatory ergonomics intervention in changing unsatisfactory psychosocial working conditions.
If organisational reforms are expected to occur, it is worthwhile taking caution with the implementation of other workplace interventions at the same time.
Acknowledgments
The authors thank other members of the ERGO research group: Samuel Dadzie, Tomi Järvinen, Ritva Lehto, Mika Nyberg, Jarmo Sillanpää, Anne Ranta and Riikka Ranta. We would like to express our warmest gratitude to the collaborating parties, the municipalities of Espoo, Tampere, Turku and Vantaa.
References
Footnotes
Funding The Academy of Finland (Health Promotion Research Programme), the Finnish Work Environment Fund, the Ministry of Labour and the Local Government Pensions Institution supported the study.
Competing interests None.
Ethics approval This study was conducted with the approval of the Ethics Committee of the Finnish Institute of Occupational Health.
Provenance and peer review Not commissioned; externally peer reviewed.
Policy-implications The findings of the present trial do not support the efficacy of this kind of participatory ergonomic intervention in changing unsatisfactory psychosocial working conditions. If organisational reforms occur simultaneously, it may be worthwhile to be cautious with the implementation of separate workplace interventions.