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The trade-off between feasibility and accuracy of measurements of physical exposure at the workplace has often been discussed, but is unsufficiently understood. We therefore explored the effect of two low-back loading measurement tools with different accuracies on exposure estimates and their associations with low-back pain (LBP). Low-back moments of 93 workers were obtained using two methods: a moderately accurate observation-based method and a relatively more accurate video-analysis method. Group-based exposure metrics were assigned to a total of 1131 workers who reported on their LBP status during three follow-up years. The two methods were compared regarding individual and group-based moments and their predictive value for LBP. Differences between the two methods for peak moments were high at the individual level and remained substantial at group level. For cumulative moments, differences between the two methods were attenuated as random inaccuracies cancelled out. Peak moments were not predictive for LBP in any method while cumulative moments were, suggesting comparable predictive values of the two methods. While assessment of low-back load improves from investing in collecting relatively more accurate individual-based data, this does not necessarily lead to better predictive values on a group level, especially not for cumulative loads., (Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.)

Purpose: The objective of the present study is to investigate the effects of a worksite health promotion intervention on musculoskeletal symptoms, physical functioning, work ability, work-related vitality, work performance, and sickness absence., Methods: In a randomized controlled design, 314 construction workers were randomized into an intervention group (n = 162) receiving personal coaching, tailored information, and materials, and a control group (n = 152) receiving usual care. Sickness absence was recorded continuously in company records, and questionnaires were completed before, directly after the 6-month intervention period, and 12 months after baseline measurements. Linear and logistic regression analyses were performed to determine intervention effects., Results: No significant changes at 6 or 12 months of follow-up were observed in musculoskeletal symptoms, physical functioning, work ability, work-related vitality, work performance, and sickness absence as a result of the intervention., Conclusions: This study shows that the intervention was not statistically significantly effective on secondary outcomes. Although the intervention improved physical activity, dietary, and weight-related outcomes, it was not successful in decreasing musculoskeletal symptoms and improving other work-related measures. Presumably, more multifaceted interventions are required to establish significant change in these outcomes.

Objectives: Exposure-outcome studies, for instance on work-related low-back pain (LBP), often classify workers into groups for which exposures are estimated from measurements on a sample of workers within or outside the specific study. The present study investigated the influence on bias and power in exposure-outcome associations of the sizes of the total study population and the sample used to estimate exposures., Methods: At baseline, lifting, trunk flexion, and trunk rotation were observed for 371 of 1131 workers allocated to 19 a-priori defined occupational groups. LBP (dichotomous) was reported by all workers during 3 years of follow-up. All three exposures were associated with LBP in this parent study (P < 0.01). All 21 combinations of n = 10, 20, 30 workers per group with an outcome, and k = 1, 2, 3, 5, 10, 15, 20 workers actually being observed were investigated using bootstrapping, repeating each combination 10000 times. Odds ratios (OR) with P values were determined for each of these virtual studies. Average OR and statistical power (P < 0.05 and P < 0.01) was determined from the bootstrap distributions at each (n, k) combination., Results: For lifting and flexed trunk, studies including n ≥ 20 workers, with k ≥ 5 observed, led to an almost unbiased OR and a power >0.80 (P level = 0.05). A similar performance required n ≥ 30 workers for rotated trunk. Small numbers of observed workers (k) resulted in biased OR, while power was, in general, more sensitive to the total number of workers (n)., Conclusions: In epidemiologic studies using a group-based exposure assessment strategy, statistical performance may be sufficient if outcome is obtained from a reasonably large number of workers, even if exposure is estimated from only few workers per group., (© The Author 2014. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.)

Objectives: Reported associations of physical exposures during work (eg, lifting, trunk flexion or rotation) and low-back pain (LBP) are rather inconsistent. Mechanical back loads (eg, moments on the low back) as a result of exposure to abovementioned risk factors have been suggested to be important as such loads provide a more direct relationship with tissue failure and thus LBP. Since information on the effect of such load metrics with LBP is lacking yet, we aimed to assess this effect in a prospective study., Methods: Of 1131 workers, categorised into 19 groups, LBP was prospectively assessed over 3 years. Video and hand force recordings of 4-5 workers per group (93 in total) were used to estimate mechanical low-back loads (peak load and three cumulative load metrics, ie, linear weighted load, squared weighted load and load weighted to the tenth power) during manual materials handling (MMH) tasks using a video analysis method. These data were combined with static mechanical load estimates based on structured observation of non-MMH tasks. Associations of mechanical loads and LBP were tested using generalised estimating equations., Results: Significant effects on LBP were found for cumulative low-back moments (linear and squared weighted; both p<0.01 and ORs of 3.01 and 3.50, respectively) but not for peak and cumulative moments weighted to the tenth power., Conclusions: Results of this first prospective study on the effect of mechanical low-back load on LBP support a LBP aetiology model of cumulative loads, potentially due to accumulation of microdamage or fatigue. Therefore, prevention of LBP should focus on reducing cumulative low-back loads, especially in highly exposed occupational groups, for example, by reducing handling of heavy loads and working in awkward body postures.

Background: To prolong sustainable healthy working lives of construction workers, a prevention program was developed which aimed to improve the health and work ability of construction workers. The objective of this study was to analyze the cost-effectiveness and financial return from the employers' perspective of this program., Methods: A total of 293 workers in 15 departments were randomized to the intervention (n = 8 departments) or control group (n = 7). Data on work ability and health were collected using questionnaires. Sick leave data were obtained from the companies. Both the cost-effectiveness analyses and return on investment analyses were performed., Results: After 12 months, the absenteeism costs were significantly lower in the intervention group than in the control group. At 12-month follow-up, no significant differences were found with respect to the primary outcomes (work ability, mental and physical health status) and secondary outcomes (musculoskeletal symptoms), meaning that the intervention was not cost-effective in comparison with the control group. The net-benefit was €641 per worker, and the intervention generated a positive financial return to the employer., Conclusion: The intervention in the present study was cost-saving to the employer due to reduced sickness absenteeism costs in the intervention group compared with the control group. However, the intervention cannot be regarded as cost-effective as no significant effects were found for work ability and health., (© 2013 Wiley Periodicals, Inc.)

Background: The prevalence of both overweight and musculoskeletal disorders (MSD) in the construction industry is high. Many interventions in the occupational setting aim at the prevention and reduction of these health problems, but it is still unclear how these programmes should be designed. To determine the effectiveness of interventions on these health outcomes randomised controlled trials (RCTs) are needed. The aim of this study is to systematically develop a tailored intervention for prevention and reduction of overweight and MSD among construction workers and to describe the evaluation study regarding its (cost-)effectiveness., Methods/design: The Intervention Mapping (IM) protocol was applied to develop and implement a tailored programme aimed at the prevention and reduction of overweight and MSD. The (cost-) effectiveness of the intervention programme will be evaluated using an RCT. Furthermore, a process evaluation will be conducted. The research population will consist of blue collar workers of a large construction company in the Netherlands., Intervention: The intervention programme will be aimed at improving (vigorous) physical activity levels and healthy dietary behaviour and will consist of tailored information, face-to-face and telephone counselling, training instruction (a fitness "card" to be used for exercises), and materials designed for the intervention (overview of the company health promoting facilities, waist circumference measuring tape, pedometer, BMI card, calorie guide, recipes, and knowledge test). MAIN STUDY PARAMETERS/ENDPOINTS: The intervention effect on body weight and waist circumference (primary outcome measures), as well as on lifestyle behaviour, MSD, fitness, CVD risk indicators, and work-related outcomes (i.e. productivity, sick leave) (secondary outcome measures) will be assessed., Discussion: The development of the VIP in construction intervention led to a health programme tailored to the needs of construction workers. This programme, if proven effective, can be directly implemented., Trial Registration: Netherlands Trial Register (NTR): NTR2095.

Objective: To evaluate the process of a prevention program among construction workers., Methods: The program consisted of training sessions of a physical therapist and an empowerment trainer, and a Rest-Break Tool. Data on seven process items were collected by means of questionnaires and interviews., Results: Recruiting construction companies to participate was difficult. The therapists and trainer largely provided the training sessions as intended, but the Rest-Break Tool was poorly implemented. Construction workers (n = 171) showed high reach (84%) and moderate attendance rates (three of four sessions). Sixty-four percent of the construction workers recommended the overall program to colleagues. Company size, economic recession, engagement of the management, and intervention year influenced dose delivered and satisfaction., Conclusions: The study showed a successful reach, dose and fidelity, and moderate satisfaction. Furthermore, contextual factors played an important role during the implementation.

Purpose: The purpose of this study was to apply the Intervention Mapping approach as a framework in the development of a worksite intervention to improve the work ability of construction workers., Design: Development of an intervention by using the Intervention Mapping approach., Setting: Construction worksite., Participants: Construction workers aged 45 years and older., Measures and Analysis: According to the principles of Intervention Mapping, evidence from the literature was combined with data collected from stakeholders (e.g., construction workers, managers, providers)., Results: The Intervention Mapping approach resulted in an intervention with the following components: (1) two individual visits of a physical therapist to lower the physical workload, (2) a Rest-Break tool to improve the balance between work and recovery, and (3) two empowerment training sessions to increase the range of influence at the worksite., Conclusions: Application of Intervention Mapping in the development of a worksite prevention program was useful in the construction industry to obtain a positive attitude and commitment. Stakeholders could give input regarding the program components as well as provide specific leads for the practical intervention strategy. Moreover, it also gives insight in the current theoretical and empirical knowledge in the field of improving the work ability of older workers in the construction industry.

Objectives: This study investigated the effectiveness of the Stay@Work participatory ergonomics programme to reduce workers' exposure to psychosocial and physical risk factors., Methods: 37 departments (n=3047 workers) from four Dutch companies participated in this cluster randomised controlled trial; 19 (n=1472 workers) were randomised to an intervention group (participatory ergonomics) and 18 (n=1575 workers) to a control group (no participatory ergonomics). During a 6 h meeting guided by an ergonomist, working groups devised ergonomic measures to reduce psychosocial and physical workload and implemented them within 3months in their departments. Data on psychosocial and physical risk factors for low back pain and neck pain were collected at baseline and after 6 months. Psychosocial risk factors were measured using the Job Content Questionnaire and physical risk factors using the Dutch Musculoskeletal Questionnaire. Intervention effects were studied using multilevel analysis., Results: Intervention group workers significantly increased on decision latitude (0.29 points; 95% CI 0.07 to 0.52) and decision authority (0.16 points; 95% CI 0.04 to 0.28) compared to control workers. However, exposure to awkward trunk working postures significantly increased in the intervention group (OR 1.86; 95% CI 1.15 to 3.01) compared to the control group. No significant differences between the intervention and control group were found for the remaining risk factors. After 6months, loss to follow-up was 35% in the intervention group and 29% in the control group., Conclusion: Participatory ergonomics was not effective in reducing exposure to psychosocial and physical risk factors for low back pain and neck pain among a large group of workers., Trial Registration: ISRCTN27472278.

Objectives: In both science and media, the adverse effects of a long duration of computer use at work on musculoskeletal health have long been debated. Until recently, the duration of computer use was mainly measured by self-reports, and studies using more objective measures, such as software-recorded computer duration, were lacking. The objective of this study was to examine the association between duration of computer use at work, measured with software and self-reports, and the onset of severe arm-wrist-hand and neck-shoulder symptoms., Methods: A 2-year follow-up study was conducted between 2004 and 2006 among 1951 office workers in The Netherlands. Self-reported computer duration and other risk factors were collected at baseline and at 1-year follow-up. Computer use at work was recorded continuously with computer software for 1009 participants. Outcome questionnaires were obtained at baseline and every 3 months during follow-up. Cases were identified based on the transition within 3 months of no or minor symptoms to severe symptoms., Results: Self-reported duration of computer use was positively associated with the onset of both arm-wrist-hand (RR 1.9, 95% CI 1.1 to 3.1 for more than 4 h/day of total computer use at work) and neck-shoulder symptoms (RR 1.5, 95% CI 1.1 to 2.0 for more than 4 h/day of mouse use at work). The recorded duration of computer use did not show any statistically significant association with the outcomes., Conclusions: In the present study, no association was found between the software-recorded duration of computer use at work and the onset of severe arm-wrist-hand and neck-shoulder symptoms using an exposure window of 3 months. In contrast, a positive association was found between the self-reported duration of computer use at work and the onset of severe arm-wrist-hand and neck-shoulder symptoms. The different findings for recorded and self-reported computer duration could not be explained satisfactorily.

Background: A worksite prevention program was developed to promote the work ability of construction workers and thereby prolong a healthy working life. The objective of this paper is to present the design of a randomized controlled trial evaluating the effectiveness of that intervention program compared with usual care for construction workers., Methods: The study is designed as a randomized controlled trial with a follow-up of one year. Employees eligible for this study are construction workers performing actual construction work. The worksite intervention will be compared with usual care. This intervention was developed by using the Intervention Mapping approach and consists of the following components: (1) two individual training sessions of a physical therapist to lower the physical workload, (2) a Rest-Break tool to improve the balance between work and recovery, and (3) two empowerment training sessions to increase the influence of the construction workers at the worksite. Outcome measures are assessed at baseline, 3, 6, and 12 months. The primary outcome measures of this study are work ability and health-related quality of life. Secondary outcome measures include need for recovery, musculoskeletal complaints, work engagement and self efficacy. Cost-effectiveness will be evaluated from the company perspective. Moreover, a process evaluation will be conducted., Discussion: The feasibility of the intervention and the study has been enhanced by creating an intervention program that explicitly appeals to construction workers and will not interfere too much with the ongoing construction. The feasibility and effectiveness of this worksite prevention program will be investigated by means of an effect- and a process evaluation. If proven effective, this worksite prevention program can be implemented on a larger scale within the construction industry., Trial Registration: NTR1278.

Background: Arm, shoulder and neck symptoms are very prevalent among computer workers. In an attempt to reduce these symptoms, a large occupational health service in the Netherlands developed a preventive programme on exposure to risk factors, prevalence of arm, shoulder and neck symptoms, and sick leave in computer workers. The purpose of this study was to assess the effectiveness of this intervention programme., Methods: The study was a randomised controlled trial. The participants were assigned to either the intervention group or the usual care group by means of cluster randomisation. At baseline and after 12 months of follow-up, the participants completed the RSI QuickScan questionnaire on exposure to the risk factors and on the prevalence of arm, shoulder and neck symptoms. A tailor-made intervention programme was proposed to participants with a high risk profile at baseline. Examples of implemented interventions are an individual workstation check, a visit to the occupational health physician and an education programme on the prevention of arm, shoulder and neck symptoms. The primary outcome measure was the prevalence of arm, shoulder and neck symptoms. Secondary outcome measures were the scores on risk factors for arm, shoulder and neck symptoms and the number of days of sick leave. Sick leave data was obtained from the companies. Multilevel analyses were used to test the effectiveness., Results: Of the 1,673 persons invited to participate in the study, 1,183 persons (71%) completed the baseline questionnaire and 741 persons participated at baseline as well as at 12-month follow-up. At 12-month follow-up, the intervention group showed a significant positive change (OR = 0.48) in receiving information on healthy computer use, as well as a significant positive change regarding risk indicators for work posture and movement, compared to the usual care group. There were no significant differences in changes in the prevalence of arm, shoulder and neck symptoms or sick leave between the intervention and usual care group., Conclusions: The effects of the RSI QuickScan intervention programme were small, possibly as a result of difficulties with the implementation process of the proposed interventions. However, some significant positive effects were found as to an increase in receiving education and a decrease in exposure to adverse postures and movements. With regard to symptoms and sick leave, only small and non-significant effects were found., Trial Registration: Netherlands National Trial Register NTR1117.

This prospective four-wave study examined (i) the causal direction of the longitudinal relations among job demands, job control, sleep quality and fatigue; and (ii) the effects of stability and change in demand-control history on the development of sleep quality and fatigue. Based on results of a four-wave complete panel study among 1163 Dutch employees, we found significant effects of job demands and job control on sleep quality and fatigue across a 1-year time lag, supporting the strain hypothesis (Demand-Control model; Karasek and Theorell, Basic Books, New York, 1990). No reversed or reciprocal causal patterns were detected. Furthermore, our results revealed that cumulative exposure to a high-strain work environment (characterized by high job demands and low job control) was associated with elevated levels of sleep-related complaints. Cumulative exposure to a low-strain work environment (i.e. low job demands and high job control) was associated with the highest sleep quality and lowest level of fatigue. Our results revealed further that changes in exposure history were related to changes in reported sleep quality and fatigue across time. As expected, a transition from a non-high-strain towards a high-strain job was associated with a significant increase in sleep-related complaints; conversely, a transition towards a non-high-strain job was not related to an improvement in sleep-related problems.

The aim of this study was to determine the internal consistency, test-retest reliability and concurrent validity of the RSI QuickScan, a newly developed questionnaire that aims to identify the presumed risk factors for neck, shoulder and arm symptoms in a population of computer workers. The internal consistency was calculated using item analysis. The test-retest reliability and concurrent validity were analysed by calculating the percentage of agreement, Cohen's Kappa and the Ppositive and Pnegative. The concurrent validity was also tested by comparing the results from the new questionnaire with those from the original questionnaires that the current questionnaire was based on, on-site expert observations and direct measurements. The results indicate that the RSI QuickScan is a measurement tool with acceptable internal consistency, reliability and concurrent validity. The questionnaire can be used as a means to rapidly collect data on a large population of office workers and at low cost.

Objectives: The objective of this study was to determine whether there are gender differences in the effect of exposure to work-related physical and psychosocial risk factors on low back, neck, shoulder, or hand-arm symptoms and related sickness absence., Methods: Data of a prospective cohort (study on musculoskeletal disorders, absenteeism stress and health) with a follow-up period of three years were used. Questionnaires were used to assess exposure to risk factors and musculoskeletal symptoms. Sickness absence was registered continuously. Female-to-male gender ratios (GR) were calculated to determine whether there were any differences in the effect. A GR value >1.33 or <0.75 was regarded as relevant., Results: Except for the effect of bending the wrist and the neck backwards (GR 1.52-2.55), men generally had a higher risk of symptoms (GR range 0.50-0.68) with equal exposure. For sickness absence, a GR value of >1.33 was found for twisting the upper body, working in uncomfortable postures, twisting the wrist, bending the neck backwards, and coworker and supervisor support (GR range 1.66-2.63). For driving vehicles, hand-arm vibration, squeezing, working above shoulder level or below knee level, reaching, twisting the neck, job demands, and skill discretion, the GR value was <0.75. For job satisfaction, a GR value of 0.50 was found for absence due to back symptoms, while the GR value was 1.78 for sickness absence due to neck, shoulder, or hand-arm symptoms., Conclusions: Although women are expected to be more vulnerable to exposure to work-related risk factors, the results of this study show that, in many cases, men are more vulnerable. This study could not explain the gender difference in musculoskeletal symptoms among workers.

Objectives: This study investigated whether work dedication and job resources are longitudinally related to work-related musculoskeletal disorders and whether job resources buffer the impact of job demands on these disorders?, Methods: Data were used from a longitudinal three-phase study (2004, 2005, 2006) on health at work among a sample of Dutch workers. The first survey was sent in 2004 by e-mail to 3100 members of an existing panel. For the analyses, 1522 participants were included with full longitudinal data. The analyses were performed using an autoregressive model with generalized estimating equations., Results: The job-resource quality of communication was found to predict the risk of work-related musculoskeletal disorders over time. This effect was not mediated by work dedication. A high quality of communication was also found to buffer the negative effects of a high physical workload on the risk of work-related musculoskeletal disorders. Furthermore, a low level of social support by colleagues was found to buffer the negative effect of a medium physical workload on work-related musculoskeletal disorders., Conclusions: This study shows that job resources are not only important for promoting work dedication, but may also moderate the negative impact of high job demands on the risk of work-related musculoskeletal disorders. With respect to social support, the question is raised of whether this can also work negatively. The results of this study imply that, besides avoiding or reducing risks to health in the workplace and lowering job demands, strengthening job resources may additionally buffer harmful effects of job demands on musculoskeletal health.

Objective: The objective of this study was to determine what makes men and women with musculoskeletal complaints decide to call in sick for work., Methods: Qualitative, face-to-face interviews were used with employees (16 men and 14 women) who had called in sick due to a musculoskeletal complaint and who expected to be absent from work for at least 2 weeks on sick leave., Results: The participants fell into the following two main groups: those who were off sick because of a diagnosed medical condition, such as a fracture, and those who were off sick because of an unidentifiable complaint, such as low-back pain. Employees in the former group called in sick because they were in the hospital or because they reckoned that their condition was too serious to warrant a continuation of work. Employees in the latter group felt hesitant and insecure and found it hard to judge whether absenteeism was justified. They decided either to "play it safe" and stay off work to prevent the complaints from worsening or to seek advice from medical professionals. Their advice did not include explicit instructions to stay at home, but were usually interpreted as such. Finally, women, but not men, were likely to call in sick if they felt that their home situation was being negatively affected by attempts to keep working while suffering physical complaints., Conclusions: The decision to call in sick is not taken lightly. Employees with nonspecific disorders base their decision on several factors, including advice from medical professionals. A factor found only among women was work-home interference.

Worldwide, millions of office workers use a computer. Reports of adverse health effects due to computer use have received considerable media attention. This systematic review summarises the evidence for a relationship between the duration of work time spent using the computer and the incidence of hand-arm and neck-shoulder symptoms and disorders. Several databases were systematically searched up to 6 November 2005. Two reviewers independently selected articles that presented a risk estimate for the duration of computer use, included an outcome measure related to hand-arm or neck-shoulder symptoms or disorders, and had a longitudinal study design. The strength of the evidence was based on methodological quality and consistency of the results. Nine relevant articles were identified, of which six were rated as high quality. Moderate evidence was concluded for a positive association between the duration of mouse use and hand-arm symptoms. For this association, indications for a dose-response relationship were found. Risk estimates were in general stronger for the hand-arm region than for the neck-shoulder region, and stronger for mouse use than for total computer use and keyboard use. A pathophysiological model focusing on the overuse of muscles during computer use supports these differences. Future studies are needed to improve our understanding of safe levels of computer use by measuring the duration of computer use in a more objective way, differentiating between total computer use, mouse use and keyboard use, attaining sufficient exposure contrast, and collecting data on disability caused by symptoms.

Study Design: Population-based randomized controlled trial., Objective: To assess the effectiveness of workplace intervention and graded activity, separately and combined, for multidisciplinary rehabilitation of low back pain (LBP)., Summary of Background Data: Effective components for multidisciplinary rehabilitation of LBP are not yet established., Methods: Participants sick-listed 2 to 6 weeks due to nonspecific LBP were randomized to workplace intervention (n = 96) or usual care (n = 100). Workplace intervention consisted of workplace assessment, work modifications, and case management involving all stakeholders. Participants still sick-listed at 8 weeks were randomized for graded activity (n = 55) or usual care (n = 57). Graded activity comprised biweekly 1-hour exercise sessions based on operant-conditioning principles. Outcomes were lasting return to work, pain intensity and functional status, assessed at baseline, and at 12, 26, and 52 weeks after the start of sick leave., Results: Time until return to work for workers with workplace intervention was 77 versus 104 days (median) for workers without this intervention (P = 0.02). Workplace intervention was effective on return to work (hazard ratio = 1.7; 95% CI, 1.2-2.3; P = 0.002). Graded activity had a negative effect on return to work (hazard ratio = 0.4; 95% CI, 0.3-0.6; P < 0.001) and functional status. Combined intervention had no effect., Conclusion: Workplace intervention is advised for multidisciplinary rehabilitation of subacute LBP. Graded activity or combined intervention is not advised.

Few studies have examined the concepts of workstyle and overcommitment in relation to the occurrence of neck and upper limb symptoms. The aim of this study was to examine whether a high-risk workstyle is a mediator in the relation of work-related exposure (job demands and computer work) and overcommitment to neck and upper limb symptoms. The study participants comprised 3,855 office workers of a European institute. The Sobel test was applied to test the intermediate effects of 4 workstyle dimensions and of the total workstyle score. The results show that most mediated effects were statistically significant, meaning that the workstyle dimensions acted as a mediator in the relation between work-related exposure and symptoms as well as in the relation between overcommitment and symptoms. Given the results with the total workstyle score, 34% of the effect of prolonged computer work, 64% of the effect of job demands, and 84% of the effect of overcommitment was mediated by workstyle. However, due to possible bias in the assessment of workstyle factor and the cross-sectional design of the study, the conclusions should be drawn with care.

Background: Successful management of workers on sick leave due to low back pain depends on the identification by the occupational physician of modifiable prognostic factors in the early phase of sick-leave. The prognostic value of factors which influence the course of low back pain and return to work in occupational health care is unclear., Methods: Secondary data analysis in a cohort of 299 workers on sick leave between 3 and 6 weeks due to low back pain was applied. We investigated the association of a broad set of prognostic indicators related to characteristics of worker, job, low back pain and psychosocial issues on return to work lasting at least 4 weeks (lasting-RTW) and minimally 1 day of first return to work (first-RTW). Relationships were studied using Cox regression analysis and covered a follow-up period of 12 months. The explained variation of the models was also calculated., Results: The median time to return to work using lasting-RTW and first-RTW was 76 and 71 days respectively. In addition to individual analysis of potential predictive factors a backward selection procedure resulted in the following multivariable model: self-predicted timing of return to work, pain intensity, job satisfaction, social support, pain radiation, expectations of treatment succes of the occupational physician. Similar results were found for first-RTW. The explained variance of the multivariate model of lasting-RTW was 18%., Conclusions: Factors concerning the expectations and beliefs of the worker affected the RTW process. Knowledge of these factors by the occupational physician in the early phase of low back pain and sick-leave may contribute to solutions to promote return to work.

Objective: To evaluate the cost-effectiveness and cost-utility of a return to work (RTW) program for workers on sick-leave due to low back pain (LBP), comparing a workplace intervention implemented between 2 to 8 weeks of sick-leave with usual care, and a clinical intervention after 8 weeks of sick-leave with usual care., Design: Economic evaluation alongside a randomised controlled trial (RCT)., Study Population: Workers sick-listed for a period of 2 to 6 weeks due to LBP., Interventions: 1. workplace assessment, work modifications and case management). 2. physiotherapy based on operant behavioural principles. 3. usual care: provided by an occupational physician., Outcomes: The primary outcome was return to work (RTW). Other outcomes were pain intensity, functional status, quality of life and general health. The economic evaluation was conducted from a societal perspective. Outcomes were assessed at baseline (after 2-6 weeks on sick-leave), and 12 weeks, 26 weeks, and 52 weeks after the first day of sick-leave., Results: The workplace intervention group returned to work 30.0 days (95% CI=[3.1, 51.3]) earlier on average than the usual care group at slightly higher direct costs (ratio of 1 day: 19 euro). Workers in the clinical intervention group that had received usual care in the first 8 weeks returned to work 21.3 days (95% CI= [-74.1, 29.2]) later on average. The group that had received the workplace intervention in the first 8 weeks and the clinical intervention after 8 weeks returned to work 50.9 days (95% CI=[-89.4, -2.7]) later on average. A workplace intervention was more effective than usual care in RTW at slightly higher costs and was equally effective as usual care at equal costs on other outcomes. A clinical intervention was less effective than usual care and associated with higher costs., Conclusion: The workplace intervention results in a safe and faster RTW than usual care at reasonable costs for workers on sick-leave for two to six weeks due to LBP.

Work related neck and upper limb symptoms have a multi-factorial origin. Possible risk factors are of a physical, psychosocial or personal origin. These factors can reinforce each other and their influence can also be mediated by cultural or societal factors. Initially, most research on neck and upper limb symptoms focused on work-related physical exposure. Nowadays, psychosocial work characteristics are recognized as important risk factors. Various models have been developed to offer frameworks for possible pathways, but their empirical support is still not conclusive. In part I of this paper an overview is presented of the results of recent epidemiological studies on work related psychosocial and personal risk factors for neck and upper limb symptoms. In addition, the interplay between these factors and the possible intermediate role of an individuals work style in this process is explored. In contrast to previous reviews, it is now possible to base the conclusions on the effect of work related psychosocial factors on neck and upper limb symptoms on quite a few longitudinal studies. These studies show that high work demands or little control at work are often related to these symptoms. However, this relationship is neither very strong nor very specific. Perceived stress is studied in not as many studies but more consistently related to neck and upper limb symptoms. This also applies to general distress or other pain (co-morbidity). Job dissatisfaction does not contribute to neck and upper limb symptoms. Too little research on personal characteristics is available to draw any conclusions. It is plausible that behavioural aspects, such as work style, are of importance in the etiology of work related upper limb symptoms. However, studies concerning these factors are promising but too scarce to draw conclusions. Future studies should address these behavioural aspects. In part II, the recent studies on the effectiveness of preventive measures for work related neck and upper limb problems are discussed. Few randomised or non randomised controlled trials have been carried out to evaluate the effectiveness of individual or organisational interventions to improve work related psychosocial factors. Very few have reported on the preventive effect for work related neck and upper limb symptoms. Therefore, there is a great need for additional high quality trials before any conclusions on effectiveness of bio-behavioural interventions for reduction of neck and upper limb problems and return to work after these symptoms can be made. From the low back pain intervention research can be learned that interventions should best be targeted to both the worker and the organisation and that interventions will only be successful when all stakeholders are involved.

Aims: To investigate the longitudinal relation between strenuous leisure time physical activity and psychological complaints (depression and emotional exhaustion) in a Dutch working population in order to find evidence for the preventive role of physical activity in the development of psychological complaints., Methods: All data came from the Study on Musculoskeletal disorders, Absenteeism, Stress, and Health (SMASH), a three year follow up study that started between 1994 and 1995. The study population consisted of 1747 workers from 34 companies. Generalised estimating equation (GEE) analyses were performed to investigate the longitudinal relation between strenuous leisure time physical activity and psychological complaints using models with and without a time lag. Logistic regression analyses were performed to study the relation between physical activity and sickness absence due to psychological complaints during the three year follow up study., Results: Only in workers with a sedentary job was strenuous leisure time physical activity (1-2 times per week) significantly associated with a reduced risk of future depression and emotional exhaustion. This was not the case for physical activity at higher frequencies (> or =3 times per week). There was a dose-response relation between strenuous leisure time physical activity and poor general health which was strongest in workers with a sedentary job. Strenuous leisure time physical activity (1-2 times per week) was associated with a lower risk of long term absenteeism (>21 days), whereas physical activity at a higher frequency was not., Conclusions: Results suggest that strenuous leisure time physical activity might play a role in the prevention of future psychological complaints, poor general health, and long term absenteeism in a working population. Workers with a sedentary job seem to benefit more from strenuous leisure time physical activity than workers without a sedentary job.

Background: Information on prognostic factors for duration of sick leave due to low-back pain (LBP) is growing. In this prospective cohort study prognostic factors for duration of sick leave and course of disability were identified in a very early stage of sick leave due to LBP in an occupational health care setting., Methods: A total of 615 workers calling in sick from work due to LBP at an occupational health service (OHS) of one institution completed a questionnaire. Duration of follow-up was 26 weeks. Prognostic factors were identified by means of Cox regression analysis and multiple linear regression analysis, and explained variance was calculated., Results: Median time to first return to work (RTW) was 5 days (Inter Quartile Range (IQR) = 2-12). Median time to lasting return to work (LRTW) was 6 days (IQR = 3-13). The final model for delayed RTW included self-reported expected duration of sick-leave, treatment by GP or specialist, care-seeking, diminished mobility, and the interaction between care-seeking and diminished mobility. The final model for LRTW included: self-reported expected duration of sick-leave, treatment by GP or specialist, care-seeking, the interaction between the self-reported expected duration of sick-leave and seeking care at OHS, complaints due to job stress, diminished mobility, and the interactions between expected duration of more then 10 days and seeking OP care and diminished mobility. Median total days on sick leave (TDSL) was 6 days (IQR = 3-13 days). The final model for TDSL included: age, expected duration of sick leave, treatment by GP or medical specialist, seeking OP care, complaints due to physical load, and diminished mobility. Explained variance (R2) of these models ranged from 30 to 35%., Conclusions: Poor prognosis for duration of sick leave can be identified by means of a simple questionnaire administered on the first day of sick leave. Workers at high risk for longer duration of sick leave (all outcomes) expected to stay off work longer, were already being treated by a MD, sought OP care, and had diminished mobility. In case of delayed LRTW workers reported job stress as a possible cause of sick leave. Interactions were found in both RTW and LRTW between care-seeking and diminished mobility and in LRTW between expected duration of sick leave and seeking OP care. Older age increased TDSL with borderline significance.

Objectives: The aim of this study was to investigate the effect of raised bricklaying on physical workload, reported musculoskeletal disorders, sickness absence, and job satisfaction., Methods: A controlled intervention study with a follow-up period of 10 months was performed among 202 bricklayers from 25 construction companies., Results: The introduction of devices for raised bricklaying decreased the physical load on the lower back and, to a less extent, on the shoulders and upper extremities. Although raised bricklaying had no effect on the number of lifts, decreases in trunk bending lowered the biomechanical moment. The results showed no decrease in reported musculoskeletal symptoms as a result of the adoption of raised bricklaying. Irrespective of the reason(s), the percentage of bricklayers in the intervention group reporting sickness absence was significantly lower than the same percentage in the control group. The results also showed that, in general, the bricklayers in this study were very satisfied with the use of devices for raised bricklaying., Conclusions: Controlled intervention studies on ergonomic improvements are rare. This study shows that the introduction of an ergonomic improvement in the construction industry may reduce physical load and the incidence of sickness absence.

Background: To describe the design of a population based randomized controlled trial (RCT), including a cost-effectiveness analysis, comparing participative ergonomics interventions between 2-8 weeks of sick leave and Graded Activity after 8 weeks of sick leave with usual care, in occupational back pain management., Design: An RCT and cost-effectiveness evaluation in employees sick-listed for a period of 2 to 6 weeks due to low back pain. Interventions used are 1. Communication between general practitioner and occupational physician plus Participative Ergonomics protocol performed by an ergonomist. 2. Graded Activity based on cognitive behavioural principles by a physiotherapist. 3. Usual care, provided by an occupational physician according to the Dutch guidelines for the occupational health management of workers with low back pain. The primary outcome measure is return to work. Secondary outcome measures are pain intensity, functional status and general improvement. Intermediate variables are kinesiophobia and pain coping. The cost-effectiveness analysis includes the direct and indirect costs due to low back pain. The outcome measures are assessed before randomization (after 2-6 weeks on sick leave) and 12 weeks, 26 weeks and 52 weeks after first day of sick leave., Discussion: The combination of these interventions has been subject of earlier research in Canada. The results of the current RCT will: 1. crossvalidate the Canadian findings in an different sociocultural environment; 2. add to the cost-effectiveness on treatment options for workers in the sub acute phase of low back pain. Results might lead to alterations of existing (inter)national guidelines.

In the Netherlands, work related upper-limb disorders are called Repetitive Strain Injuries (RSI). RSI is not a diagnosis but a catch-all term for symptoms and signs located in the neck, upper back, shoulder, arm, elbow, hand, wrist and fingers. These symptoms may include pain, stiffness, tingling, clumsiness, loss of co-ordination, loss of strength, skin discoloration and temperature differences. Each year, 8% of working Dutch citizens take time off work due to RSI symptoms. Although the number of people claiming disability benefit due to RSI is limited, this figure has risen consecutively over the last three years. There is consensus that repetitive work at a high frequency and possibly accompanied by exertion of force is accompanied by RSI symptoms. There are indications of a relation between visual display unit use and these symptoms. However, these relations have not been established in a longitudinal study of adequate quality. High perceived job stress and a high workload are thought to be related to RSI, and women report more symptoms than men. There is insufficient information available on the role of different coping styles, perfectionism and dealing with symptoms. There is little information on the underlying mechanisms in the development of RSI, the diagnostics, therapy and prevention. In view of the lack of clear diagnostic criteria, suggestions have been made for a standardised description of the symptoms involved in the syndrome. A multidisciplinary treatment is likely to have the most effect. In terms of prevention, an integrated approach aimed at improving the working posture, reduction of static load and job stress and at individual factors is assumed to be the most effective.

Objectives: This study investigates the relationship between physical and psychosocial load at work and sickness absence due to neck pain., Methods: A prospective cohort study with a follow-up period of 3 years (1994-1998) was performed among a working population. At the beginning of the study, physical load at work was quantified by means of video recordings. Work-related psychosocial variables were measured by means of the Job Content Questionnaire. The frequency of sickness absence due to neck pain with a minimal duration of 3 days was assessed on the basis of company registrations during the follow-up period. Altogether 758 workers were included in the analyses. Possible confounding by individual characteristics, physical load, and psychosocial load was studied., Results: Work-related neck flexion and neck rotation, low decision authority, and medium skill discretion showed statistically significant increased risks for sickness absence due to neck pain (adjusted rate ratios ranging from 1.6 to 4.2). High quantitative job demands, low skill discretion, and low job security showed nonsignificant increased risks for sickness absence due to neck pain (adjusted rate ratios of 2.0, 1.6 and 1.7, respectively). Work-related sitting, conflicting job demands, supervisor support, and co-worker support did not increase sickness absence due to neck pain., Conclusion: Work-related neck flexion, neck rotation, low decision authority, and medium skill discretion are risk factors for sickness absence due to neck pain. There are indications that high job demands, low skill discretion, and low job security are also risk factors for sickness absence due to neck pain.

Aims: To compare the results of a traditional approach using standard regression for the analysis of data from a prospective cohort study with the results of generalised estimating equations (GEE) analysis., Methods: The research was part of a three year prospective cohort study on work related risk factors for low back pain. The study population consisted of a cohort of 1192 workers with no low back pain at baseline. Information on work related physical and psychosocial factors and the occurrence of low back pain was obtained by means of questionnaires at baseline and at the three annual follow up measurements. In a traditional standard logistic regression model, physical and psychosocial risk factors at baseline were related to the cumulative incidence of low back pain during the three year follow up period. In a GEE logistic model, repeated measurements of the physical and psychosocial risk factors were related to low back pain reported at one measurement point later., Results: The traditional standard regression model showed a significant effect of flexion and/or rotation of the upper part of the body (OR = 1.8; 95% CI: 1.2 to 3.0), but not of moving heavy loads (OR = 1.4; 95% CI: 0.7 to 3.1). The GEE model showed a significant effect of both flexion and/or rotation of the upper part of the body (OR = 2.2; 95% CI: 1.5 to 3.3) and moving heavy loads (OR = 1.5; 95% CI: 1.0 to 2.4). No significant associations with low back pain were found for the psychosocial work characteristics with either method, but the GEE model showed weaker odds ratios for these variables than the traditional standard regression model., Conclusions: Results show that there are differences between the two analytical approaches in both the magnitude and the precision of the observed odds ratios.

Objective: To determine whether physical and psychosocial load at work influence sickness absence due to low back pain., Methods: The research was a part of the study on musculoskeletal disorders, absenteeism, stress, and health (SMASH), a 3 year prospective cohort study on risk factors for musculoskeletal disorders. Workers from 21 companies located throughout The Netherlands participated in the part of this study on sickness absence due to low back pain. The study population consisted of 732 workers with no sickness absences of 3 days or longer due to low back pain in the 3 months before the baseline survey and complete data on the reasons for absences during the follow up period. The mean (range) period of follow up in this group was 37 (7-44) months. Physical load at work was assessed by analyses of video recordings. Baseline information on psychosocial work characteristics was obtained by a questionnaire. Data on sickness absence were collected from company records. The main outcome measure was the rate of sickness absences of 3 days or longer due to low back pain during the follow up period., Results: After adjustment of the work related physical and psychosocial factors for each other and for other potential determinants, significant rate ratios ranging from 2.0 to 3.2 were found for trunk flexion, trunk rotation, lifting, and low job satisfaction. A dose-response relation was found for trunk flexion, but not for trunk rotation or lifting. Non-significant rate ratios of about 1.4 were found for low supervisor support and low coworker support. Quantitative job demands, conflicting demands, decision authority, and skill discretion showed no relation with sickness absence due to low back pain., Conclusions: Flexion and rotation of the trunk, lifting, and low job satisfaction are risk factors for sickness absence due to low back pain. Some indications of a relation between low social support, either from supervisors or coworkers, and sickness absence due to low back pain are also present.

Background: In 1993, an extensive review on the role of psychosocial factors in the development of musculoskeletal problems was published by Bongers et al (1993). Since then, additional reviews on this topic have been published; however, none of these focussed on upper limb problems., Methods: In this systematic review, the methodological quality of all studies was assessed and levels of evidence were apriori defined., Results: The large majority of the studies reported an association between at least one work-related psychosocial factor and adverse upper extremity symptoms or signs. High-perceived job stress was consistently associated with all upper extremity problems (UEP) in high and lower quality studies. Although not often studied, non-work-related stress was also consistently associated with UEP. In addition, there was some evidence for a relationship between high job demands and UEP, although the results did not meet the pre-set criterion for consistency., Conclusions: High job stress and non-work-related stress reactions are consistently associated with UEP. In addition, high job demands is also in most studies associated with these disorders. Firm conclusions on the role of these factors in the etiology of UEP are not possible due to the cross-sectional nature of most studies.

A questionnaire ('Dutch Musculoskeletal Questionnaire', DMQ) for the analysis of musculoskeletal workload and associated potential hazardous working conditions as well as musculoskeletal symptoms in worker populations is described and its qualities are explored using a database of 1575 workers in various occupations who completed the questionnaire. The 63 questions on musculoskeletal workload and associated potentially hazardous working conditions can be categorized into seven indices (force, dynamic and static load, repetitive load, climatic factors, vibration and ergonomic environmental factors). Together with four separate questions on standing, sitting, walking and uncomfortable postures, the indices constitute a brief overview of the main findings on musculoskeletal workload and associated potentially hazardous working conditions. Homogeneity of the indices is satisfactory. The divergent validity of the indices is fair when compared with an index of psychosocial working conditions and discomfort during exposure to physical loads. Worker groups with contrasting musculoskeletal loads can be differentiated on the basis of the indices and other factors. With respect to the concurrent validity, it appears that most indices and factors show significant associations with low back and/or neck-shoulder symptoms. This questionnaire can be used as a simple and quick inventory for occupational health services to identify worker groups in which a more thorough ergonomic analysis is indicated.

Objective: To study the relation between neck pain and work related neck flexion, neck rotation, and sitting., Methods: A prospective cohort study was performed with a follow up of 3 years among 1334 workers from 34 companies. Work related physical load was assessed by analysing objectively measured exposure data (video recordings) of neck flexion, neck rotation, and sitting posture. Neck pain was assessed by a questionnaire. Adjustments were made for various physical factors that were related or not related to work, psychosocial factors, and individual characteristics., Results: A significant positive relation was found between the percentage of the working time in a sitting position and neck pain, implying an increased risk of neck pain for workers who were sitting for more than 95% of the working time (crude relative risk (RR) 2.01, 95% confidence interval (95% CI) 1.04 to 3.88; adjusted RR 2.34, 95% CI 1.05 to 5.21). A trend for a positive relation between neck flexion and neck pain was found, suggesting an increased risk of neck pain for people working with the neck at a minimum of 20 degrees of flexion for more than 70% of the working time (crude RR 2.01, 95% CI 0.98 to 4.11; adjusted RR 1.63, 95% CI 0.70 to 3.82). No clear relation was found between neck rotation and neck pain., Conclusion: Sitting at work for more than 95% of the working time seems to be a risk factor for neck pain and there is a trend for a positive relation between neck flexion and neck pain. No clear relation was found between neck rotation and neck pain.

Study Design: A 3-year prospective cohort study among workers of 34 companies in the Netherlands., Objectives: To investigate the relation between flexion and rotation of the trunk and lifting at work and the occurrence of low back pain., Summary of Background Data: Previous studies on work-related physical risk factors for low back pain either lacked quantification of the physical load or did not take confounding by individual and psychosocial factors into account., Methods: The study population consisted of 861 workers with no low back pain at baseline and complete data on the occurrence of low back pain during the 3-year follow-up period. Physical load at work was assessed by means of analyses of video-recordings. Information on other risk factors and the occurrence of low back pain was obtained by means of self-administered questionnaires., Results: An increased risk of low back pain was observed for workers who worked with the trunk in a minimum of 60 degrees of flexion for more than 5% of the working time (RR 1.5, 95% CI 1.0-2.1), for workers who worked with the trunk in a minimum of 30 degrees of rotation for more than 10% of the working time (RR 1.3, 95% CI 0.9-1. 9), and for workers who lifted a load of at least 25 kg more than 15 times per working day (RR 1.6, 95% CI 1.1-2.3)., Conclusions: Flexion and rotation of the trunk and lifting at work are moderate risk factors for low back pain, especially at greater levels of exposure.

Study Design: A systematic review of observational studies., Objectives: To assess whether psychosocial factors at work and in private life are risk factors for the occurrence of back pain., Summary of Background Data: Several reviews on risk factors for back pain have paid attention to psychosocial factors. However, in none of the published reviews was a strict systematic approach used to identify and summarize the available evidence., Methods: A computerized bibliographical search of several databases was performed, restricted to studies with a cohort or case-control design. A rating system was used to assess the strength of the evidence for various factors, based on the methodologic quality of the studies and the consistency of the findings., Results: Eleven cohort and two case-control studies were included in this review. Strong evidence was found for low social support in the workplace and low job satisfaction as risk factors for back pain. Insufficient evidence was found for an effect of a high work pace, high qualitative demands, low job content, low job control, and psychosocial factors in private life., Conclusions: Evidence was found for an effect of low workplace social support and low job satisfaction. However, the result for workplace social support was sensitive to slight changes in the rating system, and the effect found for low job satisfaction may be a result of insufficient adjustment for psychosocial work characteristics and physical load at work. In addition, the combined evaluation of job content and job control, both aspects of decision latitude, led to strong evidence of a role for low job decision latitude. Thus, based on this review, there is evidence for an effect of work-related psychosocial factors, but the evidence for the role of specific factors has not been established yet.

This systematic review assessed aspects of physical load during work and leisure time as risk factors for back pain. Several reviews on this topic are available, but this one is based on a strict systematic approach to identify and summarize the evidence, comparable with that applied in the clinical literature on the efficacy of intervention for back pain. A computerized bibliographical search was made of several data bases for studies with a cohort or case-referent design. Cross-sectional studies were excluded. A rating system was used to assess the strength of the evidence, based on the methodological quality of 28 cohort and 3 case-referent studies and the consistency of the findings. Strong evidence exists for manual materials handling, bending and twisting, and whole-body vibration as risk factors for back pain. The evidence was moderate for patient handling and heavy physical work, and no evidence was found for standing or walking, sitting, sports, and total leisure-time physical activity.

To determine priorities for ergonomic improvements in five maintenance departments of a steel company, a study was carried out to identify groups with a high prevalence of musculoskeletal problems or a high exposure to unfavourable musculoskeletal workload. All workers were asked to complete a standardized questionnaire on musculoskeletal symptoms and musculoskeletal workload. Response rate in the five departments varied between 60 and 80% (n = 436). Symptoms of low back and neck-shoulder (12-month prevalence rates of 53% and 36%, respectively) were most common, but not higher in comparison with a reference group of 396 non-sedentary workers. Self-reported exposure rates to physical and psychosocial loads as well as poor climatic conditions were comparable with the reference group; only exposure to vibration was higher. Significant differences were seen between the five departments as well as between task groups with the departments. Several task groups with relatively high symptom rates and high exposure levels could be identified. It is concluded that a questionnaire survey can constitute a valuable contribution to the selection of high-risk task groups that need ergonomic intervention.

Objectives: This paper examines the relationship between work stressors and the following health indicators: psychosomatic complaints, health behavior, and musculoskeletal problems., Methods: Secondary analyses were performed on data from the National Work and Living Condition Survey, which provides a representative sample of the working population in The Netherlands. The survey was made in 1977, 1983, and 1986 by The Netherlands Central Bureau of Statistics. By means of factor analysis the following three risk dimensions were identified in the survey: work pace, intellectual discretion, and physical stressors., Results: High work pace, low intellectual discretion, and physical stressors were associated with increased health complaints (both psychosomatic and musculoskeletal) and musculoskeletal disorders after adjustment for gender, age, education, and sports participation. Low intellectual discretion, but not high work pace, was associated with poor general health and health behavior indicative of poor health. Physical stressors were associated with general health as well, but not with health behavior, except for reported absenteeism., Conclusions: Psychosocial stressors are not only associated with psychosomatic complaints and health indicators, but also with musculoskeletal problems, both acute and chronic. Especially the relation between intellectual discretion and musculoskeletal problems can be partly attributed to physical load. Even after adjustment for physical stressors and moderating personal characteristics, the relationships between the psychosocial stressors and musculoskeletal problems remained significant and comparable in strength to the relationship between psychosocial stressors and several other health outcomes, such as psychosomatic complaints.

The objective of this review is to establish whether the epidemiologic literature presents evidence of an association between psychosocial work factors and musculoskeletal disease. In a hypothetical model it is suggested that individual characteristics and stress symptoms can modify this relationship. The reviewed studies do not present conclusive evidence due to high correlations between psychosocial factors and physical load and to difficulties in measuring dependent and independent variables. Nevertheless, it is concluded that monotonous work, high perceived work load, and time pressure are related to musculoskeletal symptoms. The data also suggest that low control on the job and lack of social support by colleagues are positively associated with musculoskeletal disease. Perceived stress may be an intermediary in this process. In addition, stress symptoms are often associated with musculoskeletal disease, and some studies indicate that stress symptoms contribute to the development of this disease.

To study the long-term health effect of whole-body vibration, a questionnaire on symptoms of ill health was mailed to 242 drivers and a reference group of 210 workers from six harbor companies (response 81%). Vehicles driven were fork-lift trucks and freight-container tractors. Vibration level during a representative working period (vector sum of the frequency weighted acceleration in the x-, y-, and z-directions) was 0.8 m/sec2 for the fork-lift trucks and 1.0 m/sec2 for the freight-container tractors. Only the results concerning self-reported symptoms of the back are described. Of the young (less than 35 years), short-term-exposed drivers, 68% reported that they had back pain regularly vs. only 25% of the reference group of comparable age. With increasing age, the difference in the prevalence of self-reported regular back pain between the drivers and the reference group disappeared. Driving during the 5 years preceding the onset of symptoms seemed to increase the risk of back pain, whereas earlier exposure did not.

In a questionnaire survey the prevalence of back pain in 163 helicopter pilots was compared to that in a control group of 297 non-flying air force officers who underwent the same pre-employment medical examination. Since pilots document their hours of flight in a personal flight log, an accurate estimate of the duration of exposure could be made. In addition, vibration levels of the helicopters were measured and an accumulative vibration dose was calculated for each pilot. 'Transient' back pain of a short duration was more frequent amongst the pilots compared to the control group, and the prevalence of 'chronic' back pain of a persistent nature was also higher amongst the helicopter pilots. Transient back pain seemed to be most strongly related to the average hours of flight per day, whereas chronic back pain was more closely related to total hours of flight or the accumulative vibration dose. A significant higher prevalence of this chronic back pain was observed only after 2000 hours of flight or a vibration dose of 400 m2h/s4. The observed health effects may be due to vibration or constrained posture but are most likely due to concomitant exposure to both factors.

In The Netherlands so far little research has been carried out to investigate the health effects of exposure to whole-body vibration at work. In a retrospective (10-year) follow-up study, the incidence of permanent work disabilities in crane operators exposed to vibration was compared to that of a control group. The emphasis in this presentation is on disablement because of back disorders. Among the crane operators with more than 5 years of exposure to vibration, more disability due to back trouble occurred than in the control group. The incidence density ratio (IDR) exceeded 2 for disability because of degeneration of the intervertebral disc, after adjustment for age, nationality, shift work and calendar year. With increasing years of exposure, the risk ratio for disability because of intervertebral disc disorders also increased. The risk ratio for a disability pension due to disease of the intervertebral disc for crane operators with more than 5 years of exposure was almost 3 compared to the control group. A combination of exposure to whole-body vibration, an unfavorable posture, and climatic conditions is responsible for the development of these health effects.

In a retrospective (10-year) follow-up study, the incidence of at least one spell of sickness absenteeism of 28 d or longer in crane operators exposed to whole-body vibration and a control group was investigated. In contrast to a previous study on permanent work disability in the same groups, no difference was observed in long-term sickness absenteeism because of lumbar disorders. Spells of sickness absence due to intervertebral disc disorders did last longer in the index group and also more disability pensions with this diagnosis were recorded in the index group. This indicates that these disorders particularly interfere with the work of a crane operator. Exposure to whole-body vibration and strained posture are considered to be responsible for this situation.