J Occup Rehabil (2006) 16:279 302 DOI 10.1007/s10926-006-9044-1 ORIGINAL PAPER Epidemiology of work related neck and upper limb problems: Psychosocial and personal risk factors (Part I) and effective interventions from a bio behavioural perspective (Part II) P. M. Bongers S. Ijmker S. van den Heuvel B. M. Blatter Published online: 19 July 2006 C Science+Business Media, Inc. 2006 Abstract 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. P. M. Bongers S. Ijmker S. van den Heuvel B. M. Blatter TNO Quality of Life, Work and Employment, Hoofddorp, The Netherlands P. M. Bongers S. Ijmker B. M. Blatter Body@work, Research Center on Physical Activity, Work and Health TNO VU University Medical Center, Amsterdam, The Netherlands P. M. Bongers ( ) S. Ijmker Institute for Research in Extramural Medicine Institute, VU University Medical Center, Amsterdam, The Netherlands e-mail: Paulien.Bongers@tno.nl
280 J Occup Rehabil (2006) 16:279 302 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. Keywords Psychosocial factors. Neck and upper limb symptoms. Interventions. Epidemiology Introduction Prevalence Work related neck and upper limb problems are still very prevalent. In the Netherlands, a survey showed that in 2002 and 2004, 28% of the working population reported neck/shoulder or elbow/wrist/hand symptoms in the previous 12 months. These symptoms were at least partly caused by work, according to the self-report of the participants [38]. Data from the European Foundation for the Improvement of Living and Working Conditions, based on fifteen European countries, showed that 25% of the workers reported work-related neck/shoulder pain, and 15% reported work-related arm pain [22]. In the Netherlands, yearly sick leave due to work related neck and upper limb problems is estimated to be 2 to 4% of all workers. This is about 4 6% of the total number of sick days in the Netherlands. In 2001, 6% of the total number of new disability benefits in the Netherlands was due to chronic disability caused by neck and upper limb symptom, with an average duration of 3 to 4 years. However, in the most recent years incident disability for work due to neck and upper limb symptoms has decreased to 2% [113]. This may be due to the unfavourable economic climate, recent changes in eligibility or a true decline in chronic neck and upper limb disorders. Neck and upper extremity symptoms are also common in Dutch general practice. The GP is consulted approximately seven times each week for a complaint relating to the neck or upper extremity; of these, three are new complaints or new episodes [9, 10]. Total yearly costs are estimated to be 2.1 billion euro in the Netherlands. Main cost drivers are costs due to sick leave (962 miljon euro) and costs due to loss of productivity among symptomatic workers (808 miljon euro). Recent conservative estimates of the cost to the U.S. economy for all musculoskeletal disorders range from $45 to $54 billion annually (NSR/IOM 2001). Multifactorial origin Work related neck and upper limb symptoms have a multi-factorial origin. Possible risk factors are of a physical, psychosocial or personal origin. Figure 1 presents the possible relationships between these factors (adopted from [83]). These factors can reinforce each other and their influence can also be mediated by cultural or societal factors. The importance of each factor, and hence its contribution to the risk of symptoms, varies among individuals and work environments [83]. This model suggests that the psychosocial aspects of the work environment interact with
J Occup Rehabil (2006) 16:279 302 281 Work External Load Organizational Factors Social Context Biomechanical Loading Internal Tolerances Outcomes Internal Loads Physiologic Response Mechanical Strain Fatique Pain Discomfort Inpairment Disability Individual Factors Person Fig. 1 [83]) Possible relationships between risk factors of a physical, psychosocial or personal origin (adopted from the development of musculoskeletal problems through several pathways. Although the various models that have been developed, offer a framework for these pathways, their empirical support is still rather primitive [41]. This paper concentrates on the relationships between organizational factors, individual factors and work related complaints of neck and upper limb problems. In part we discuss the most recent results in the epidemiological literature about these risk factors and in part II we discuss the available evidence on effective interventions that address reduction of psychosocial and behavioural risk factors. Part 1 epidemiology of work related neck and upper limb problems: Psychosocial and personal risk factors Initially, most research on neck and upper limb symptoms focused on work-related physical exposure. These studies in industrial settings showed that repetitiveness, especially in combination with forceful exertions, is generally acknowledged as an important risk factor [83, 116]. In office workers the effect of physical load, i.e. due to posture, on neck and upper limb symptoms is less clear and most likely of modest importance. A summary of recent longitudinal studies among office workers [42], shows that mouse usage longer than 10 20 h per week is a risk factor for hand/arm symptoms, but not for neck/shoulder symptoms [3, 11, 45, 47, 54, 55, 56, 60, 74]. Nowadays, psychosocial work characteristics are recognized as important risk factors. In our systematic review in 2002 [8] we concluded that 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 and non work-related stress were consistently associated with all upper extremity problems in high and lower quality studies. In addition, high job demands were also associated with these disorders in most studies. However, firm conclusions were not possible due to the cross-sectional nature of almost all studies. Moreover, comparison of the studies was hampered by a large variation in the conceptualization, classification and measurement of the work related psychosocial factors [41]. Since 2002, more prospective studies have been published that identified psychosocial work characteristics as risk factors for neck and
282 J Occup Rehabil (2006) 16:279 302 Fig. 2 Possible relationships between risk factors of psychosocial and personal origin for neck and upper limb problems upper limb symptoms. Although also in these studies the psychosocial factors are conceptualized differently, most studies analyzed the effect of the dimensions of the demand-control-support model [48] and/or perceived stress. Another well-known stress-model for the association of psychosocial factors and stress-related health outcomes is Siegrist s Effort-Reward Imbalance (ERI) model [96 98]. One recent study also explored the relationship of the dimensions of this model on neck and upper limb problems [113]. In addition some recent studies address the role of personal characteristics and the intermediate role of personal workstyle (Fig. 2). Below we will discuss the relationship of these factors with work related neck and upper limb problems in more detail. Since our previous review [8], contained only one fairly old longitudinal study [7] we based this presentation on a systematic search of the literature for longitudinal studies of the year 2000 or later. Demand-control-support dimensions The Demand-Control-Support model hypothesizes that in particular the combination of high job demands and low control leads to stress and stress-related health outcomes. A low level of social support will enhance the adverse effects of this combination. A recent systematic review concluded that 16 of the 19 high-quality studies (84%) provided support for effects of psychosocial factors on self-report measures for poor health and/or well-being, usually seen as indicators of psychological distress. However, only modest support was found for the hypothesis that especially the combination of high demands and low control results in such symptoms. Moreover not one dimension in particular seemed to be more important than the others [21]. Since our previous review [8], twenty four longitudinal studies examined the effect of these dimensions on neck, shoulder or hand, arm symptoms either in an industrial, care, mixed or
J Occup Rehabil (2006) 16:279 302 283 office population ([2 4, 11, 13, 30, 34, 36, 43, 45, 47, 54, 55, 56, 60, 63, 64, 67, 71, 82, 85, 93, 99, 108, 111, 112, 114]. The results of these studies are summarized for neck shoulder problems in Table 1, and arm, wrist, hand studies in Table 2. It is very promising that in this relatively small time span so many prospective studies have been conducted. It should be noted however that several of these publications concern the same cohort. The results in Tables 1 and 2 show that most of these recent cohort studies identify one of the dimensions of the Karasek model as a risk factor of modest magnitude for work related neck or upper limb symptoms, also after adjustment for physical and personal factors. However, not one of these dimension is implicated in particular. Although, most studies that investigated the effect of a combination of high demands and low control (i.e., high strain), seem to report a relationship between these working conditions and neck and shoulder symptoms, but not for arm-hand problems. In most of these studies not the interaction of these factors but a combined effect was tested. In addition, the results presented in table two and three may imply that low social support is of more relevance in mixed populations than in office populations. The general conclusion is that work related psychosocial factors are modestly related to symptoms of neck and upper limb symptoms and that not one factor is implicated specifically. At this point in time it is for the first time that such an overall conclusion is substantiated by a substantial number of longitudinal studies. This conclusion is in accordance with the conclusion of De Lange et al. [21], in her review on the effect of these work related psychosocial concepts on general distress or psychological well being. This implies that although these factors are relevant for the development of neck and upper limb symptoms, independently of physical exposure, this is not a specific or a strong relationship. This may in part be due to the fact that the concepts are rather broadly defined and often interrelated. In addition, these studies have examined different contrasts in exposure. Sometimes a tertile split is chosen, contrasting the upper tertile with the lowest tertile or a small group at the high end of the scale is contrasted with a group that reports very little demands or high control. In most studies several different outcome variables are analyzed (i.e., frequency of symptoms and intensity of symptoms or several different regional pains). Effort Reward Imbalance (ERI) The assumption of the ERI-model is that an imbalance between high efforts and low rewards leads to adverse health effects, including stress and in particular cardiovascular disease [52, 59, 88]. A recent review concluded that in most studies a high-effort-low-reward situation was associated with less psychological well being (i.e., 18 out of 21 studies) [120]. Van den Heuvel and Blatter [113], showed that the psychosocial dimensions of the Effort-Reward Imbalance model also may affect neck and upper limb symptoms. This study showed that workers with high effort as well as workers with low reward reported more symptoms. The assumption of the model is that the combination of high effort and low reward is more unfavourable than the addition of their separate effects. However, no interaction effects were found in the the study of Van den Heuvel (Fig. 3). Workstress, general distress, co-morbidity, job satisfaction, depressive symptoms In our review of Bongers et al. [8], it was concluded that high-perceived job stress was consistently associated with all upper extremity problems in the available mainly cross-sectional studies. All six more recent longitudinal studies that analyzed the effect of this variable, except Korhonen et al. [54, 56], confirm this finding (Table 3). In addition, other (musculoskeletal) pain, high general distress or otherwise measured co-morbidity also seem to predict work related neck and
284 J Occup Rehabil (2006) 16:279 302 Table 1 Longitudinal associations between the demand-control-support dimensions and neck and shoulder symptoms or signs Study Type pop N/S a High demands Little control Low social support High Job strain Ariëns et al. [4] (SMASH) Mixed N 2.1 (1.3 3.6) RR 1.6 (0.7 3.4) 2.4 (1.1 5.3) RR Cassou et al. [13] Mixed N 1.2 (1.0 1.4) Rugulies and Krause [93] Transit N 1.1 (0.8 1.5) 1.3 (1.0 1.7) 1.3 (1.0 1.7) 1.5 (1.1 2.0) HR Van den Heuvel et al. [111, 112, 114] (SMASH) Mixed N/S 2.1 (1.2 3.5) 1.2 (0.7 2.2) 1.0 (0.5 1.9) 1.5 (1.0 2.4) Harkness et al. [36] Mixed S 0.9 (0.6 1.4) 1.0 (0.5 2.0) 1.0 (0.3 3.1) Leclerc et al. [64] Mixed S M: 3.7 (1.4 9.4) W: 1.5 (0.7 2.7) Torp et al. [108] Mixed + b Feveile et al. [30] Mixed N/S M: 1.8 (1.2 2.4) c W: Andersen et al. [2, 3] Industry N/S 1.5 (1.3 1.8) 1.2 (1.0 1.5) 1.0 (0.9 1.3) Ostergren et al. [85] Mixed N/S M: 1.0 (0.8 1.4) M: 0.9 (0.7 1.3) M: 1.1 (0.9 1.5) M: 1.0 (0.6 1.4) W: 1.1 (0.8 1.4) W: 1.1 (0.9 1.5) W: 1.1 (0.9 1.5) W: 1.5 (1.1 2.0) Luime et al. [67] Care N/S 1.2 (0.8 1.8) 1.4 (0.9 2.0) 1.0 (0.7 1.6) 1.5 (1.0 2.4) d Smedley et al. [99] Care N/S 0.9 (0.7 1.4) HR 1.1 (0.8 1.6) HR 0.9 (0.6 1.3) HR Ijzelenberg and Burdorf [43] Mixed N/arm 1.0 (0.6 1.7) 0.9 (0.6 1.6) 1.1 (0.7 1.6) 2.1 (1.3 3.3) Jensen [45] (BIT) Office N M: - W: 2.2 (1.3 3.7) Brandt et al. [11] (NUDATA) Office N 1.7 (1.0 2.7) 1.3 (0.8 2.2) d 1.5 (0.9 2.4) Korhonen et al. [54, 56] Office N 1.7 (0.9 3.2) d Hannan et al. [34] Office N/S 1.7 (0.9 3.0) HR Juul Kristensen et al. [47] (BIT) Office S 1.0 (0.98 1.01) e 1.0 (0.99 1.01) Brandt et al. [11] (NUDATA) Office S 1.4 (0.0 2.2) d 1.9 (1.2 2.9) 1.3 (0.8 2.1) d Note. Presented are the risk estimates with a 95% confidence interval. Most estimates are presented as odds ratio s, some were relative risks (RR) or hazard ratio s (HR). The studies that did not present the risk estimates that were not statistically significant in the multivariate analysis are represented by ; ( ) indicates that that factor was not studied in that particular study. a N: Neck, S: Shoulder, M: Male, W: Female. b Linear regression analyses. c High vs rather high 1.4 (1.0 2.1). d Unadjusted or limited adjusted risk estimate not in the final multivariate model. e This is the risk estimate for little influence at work adjusted for little influence on pauses with a risk estimate of 1.9 (1.2 2.9).
J Occup Rehabil (2006) 16:279 302 285 Table 2 Longitudinal associations between the demand-control-support dimensions and arm, wrist or hand symptoms or signs Study Popu-lation Type of complaint High demands Little control Low social support High job strain Macfarlane et al. [71] Mixed Forearm 2.0 (0.7 5.6) 2.0 (0.9 4.2) a 2.6 (1.1 5.8) Leclerc et al. [63] Mixed Upperlimb 2.5 (1.0 6.4) b Nahitetal.[82] Mixed Forearm 1.1 (0.5 2.2) 2.6 (1.1 6.1) a 1.4 (0.4 5.0) Van den Heuvel et al. [111, 112, 114] Mixed Elbow, wrist 1.9 (1.0 3.7) 0.9 (0.4 2.0) 2.2 (1.0 4.9) 1.1 (0.6 2.1) Feveile et al. [30] Mixed Wrist-hand Hannan et al. [34] Office Arm-hand 1.3 (0.6 2.9) HR Kryger et al. [55] (NUDATA) Office Forearm 1.9 (1.0 3.4) 1.0 (0.5 1.7) 1.1 (0.6 2.0) Jensen [45] (BIT) Office Wrist M: 2.5 (1.3 4.8) c W: 2.4 (1.5 3.8) Juul Kristensen et al. [47] (BIT) Office Elbow 0.99 (0.98 1.01) 1.0 (0.99 1.01) Lassen et al. [61] (NUDATA) Office Elbow 1.3 (1.0 1.7) 1.0 (0.8 1.4) 1.0 (0.9 1.4) 1.2 (0.8 1.9) Lassen et al. [61] (NUDATA) Office Wrist 1.0 (0.7 1.3) 1.3 (0.9 1.6) 1.0 (0.8 1.3) 0.9 (0.5 1.4) Andersen et al. [2, 3] (NUDATA) Office CTD 1.3 (0.9 1.8) 0.9 (0.7 1.4) 1.2 (0.9 1.8) Note. Presented are the risk estimates with a 95% confidence interval. Most estimates are presented as odds ratio s, some were relative risks (RR) or hazard ratio s (HR). The studies that did not present the risk estimates that were not statistically significant in the multivariate analysis are represented by ; ( ) indicates that that factor was not studied in that particular study. M: Male; W: Female. a Unadjusted or limited adjusted risk estimate not in the final multivariate model. b Only for wrist tendinitis (not for CTS and epicondylitis). c Medium low influence; low influence OR 1.8 (0.6 1.4).
286 J Occup Rehabil (2006) 16:279 302 35 35 30 30 ERI Symptom score 25 20 15 10 Symptom score 25 20 15 10 high effort, low reward low reward high effort no high effort, no low reward 5 5 0 baseline 1th follow-up 2nd follow-up 3th follow-up 0 baseline 1th follow-up 2nd follow-up 3th follow-up Fig. 3 Fitted values of neck/shoulder symptoms for values of the effort reward imbalance model for men (left) and women (right) upper limb problems, except in the study of Andersen et al. [2, 3], but this analysis concerns a more specific health outcome (CTD). Poor job satisfaction was not reported to be a consistent risk factor in the review of 2002 and is neither consistently related with work related neck or upper limb problems in the recent longitudinal studies. In the NUDATA study a positive association was presented, but in that study dissatisfaction with workplace design was studied. Depressive symptoms were positively associated with neck or upper limb problems in three out of five studies. Personal characteristics Next to work-related psychosocial risk factors, personality traits may contribute to the onset of neck and upper limb symptoms. Some studies found an association between neck/shoulder symptoms and type A behavior [72] while others did not ([2, 3, 55, 61]; i.e. the NUDATA study). Also introversion ([73] cross sectional), neurotic perfectionist traits ([118] case control) and illness behavior [71] were reported to be associated with work related neck and upper limb symptoms. Other factors such as negative affectivity were not associated with these problems [61]. Only the study of Macfarlane and the NUDATA study are prospective in nature. Therefore the data on personality related factors and neck and upper limb problems are still very scarce. Apart from the theory mentioned above that a combination of high effort and low reward could lead to adverse health effects, Siegrist incorporated the concept overcommitment in the ERI model. Overcommitment is a personality trait that could reinforce the unfavorable effect of effort-reward imbalance. Furthermore, overcommitment might have an independent effect. The concept overcommitment specifies those cognitive, emotional and motivational components within the global concept of Type A behavior that are important in coping with work demands. One cross-sectional study [46] used musculoskeletal symptoms as an outcome measure and found a higher prevalence of neck pain in subjects with a high score on overcommitment and in subjects with an unfavourable effort/reward-imbalance, but shoulder pain and pain in the upper extremities were associated with neither overcommitment nor ERI. The adverse effects of effort and reward were not stronger in overcommitted subjects. Recently, Van den Heuvel and Blatter [113] showed in a longitudinal study that overcommitted subjects reported more neck and upper limb symptoms, at baseline as well as during follow-up. Overcommitted workers may expose themselves more often to high demands at work, or they may exaggerate their efforts beyond what is formally needed. This suggests that an intermediate role for a so called adverse work style may be relevant.
J Occup Rehabil (2006) 16:279 302 287 Table 3 Longitudinal associations between perceived stress, distress/co-morbidity, job satisfaction and depressive symptoms and neck/shoulder or arm/hand symptom High perceived High distress Poor job Depressive Study Type pop Symptom stress Co-morbidity satisfaction symptoms Cassou et al. [14] Mixed N M: 1.3 (1.0 1.8) W: 1.5 (1.2 1.9) Harkness et al. [36] Mixed S 1.1 (0.7 1.9) 0.7 (0.2 2.1) 1.6 (1.1 2.2) a Leclerc et al. [64] Mixed S 3.8 (1.6 8.7) b W: 1.8 (0.8 3.8) b 1.6 (0.9 2.9) b Andersen et al. [2] Industry N/S 1.8 (1.4 2.5) Luime et al. [67] Mixed N/S 1.5 (1.0 2.3) N Ijzelenberg and Burdorf [43] Mixed 1.6 (1.0 2.4) Korhonen et al. [54, 56] Office N 1.0 (0.5 1.8) c 1.1 (0.5 2.3) 1.3 (0.7 2.0) Carroll et al. [13] Mixed N 4.0 (1.8 8.7) HR Croft et al. [17] Mixed 1.5 (1.0 2.2) RR d Smedley et al. [99] Nurses N/S 1.2 (0.8 1.8) HR Viikari-Juntura et al. [121] Forest workers N 1.7 (1.4 2.0) Miranda et al. [79] Forest S 1.9 (1.1 3.3) e Nahit et al.[82] (same cohort as [36]) Mixed Forearm 1.7 (0.6 4.7) Macfarlane et al. [71] Mixed Forearm 3.3 (0.7 14.2) 1.8 (0.8 4.1) 1.0 (0.4 3.0) 6.6 (1.5 29) f Leclerc et al. [63] Mixed Upper limp + + Kryger et al. [55] (NUDATA) Office Forearm 1.1 (0.4 2.7) g Lassen et al. [61] (NUDATA) Office Elbow 2.1 (1.1 3.8) h 1.9 (1.1 3.4) g Lassen et al. [61] (NUDATA) Office Wrist 1.9 (1.1 3.3) h 1.7 (1.0 2.7) g Feveile et al. [30] Mixed W/H M: 1.7 (1.1 2.7) W: 1.7 (1.1 2.4)
288 J Occup Rehabil (2006) 16:279 302 Table 3 Continued High perceived High distress Poor job Depressive Study Type pop Symptom stress Co-morbidity satisfaction symptoms Andersen et al. [2] (NUDATA) Office CTD 0.9 (0.5 1.6) 1.7 (1.0 3.1) g Note. Presented are the risk estimates with a 95% confidence interval. Most estimates are presented as odds ratio s, some were relative risks (RR) or hazard ratio s (HR). The studies that did not present the risk estimates that were not statistically significant in the multivariate analysis are represented by ; (o) indicates that that factor was not studied in that study, + indicates a significant positive association after adjustment for confounders but no risk estimate presented. M: Male; W: Female. a Other pain 1.3 (0.9 1.9) in final model. b Poor job satisfaction in final model for carpal tunnel syndrome for women, becomes significant in case of stricter diagnosis; depressive symptoms for epicondylitis; psychosomatic problems for wrist tendinitis. c Interaction stress and sedentariness 6.7 (1.0 43). d Slightly lower distress RR 1.6 (1.1 2.3). e However no association with severe shoulder pain, no data presented on that risk estimate. f Poor illness behavior. g Dissatisfied with workplace design, severe pain. h Poor medical condition.
J Occup Rehabil (2006) 16:279 302 289 Workstyle/behaviour In 2004 Feuerstein and colleagues constructed the concept work style. Work style indicates the individual responses to high work demands. It is not conceptualised as a personality factor, but rather as a learned and reinforced strategy for completing, responding to, or coping with increased job demands that may affect musculoskeletal health [28, 29]. A high-risk work style implies: taking shorter or fewer breaks or even skip breaks, working through pain, anticipating the possible negative reactions of colleagues, and making high demands on one s own performances at work. Exposure at work combined with specific personality traits could induce a high-risk work style and this work style may lead to neck and upper limb symptoms. Empirical evidence of the effect of the work style concept is still scarce. Preliminary analyses, before the concept was defined explicitly, have shown that poor work style could have an adverse effect on musculoskeletal symptoms [28]. In another study an association between work style and pain severity was found in a population of symptomatic female office workers [37]. Van den Heuvel and Blatter [113], reported in a cross-sectional study that a high-risk work style (measured with a short form of the original workstyle concept) was associated with both unfavorable working conditions (i.e. high job demands and prolonged VDU-work) and with neck and upper limb symptoms. The results of a recent longitudinal study showed that an adverse work style predicted upper extremity symptoms and functional limitations at 3 months [84]. Interrelations Several authors have suggested possible pathways through which psychosocial factors might contribute to the onset (and perpetuation of) neck and upper limb symptoms [87, 125]. One of the possible explanations is that adverse psychosocial work characteristics may lead to an increased physical load (external). For example, high job demands may lead to an increase in the frequency and duration of exposure (i.e., longer working hours, fewer rest breaks, but also to changes in posture, movement or exerted forces). In the study of Van den Heuvel et al. [112], the estimated effects of psychosocial factors on neck and upper limb symptoms, in the multivariate analyses, decreased after the adjustment for physical exposure, indicating that the observed risk was partly due to an increase in physical load associated with the high job demands and the health outcomes. It is interesting to note however, that in that study, the adjustment for physical risk factors in the multivariate model, resulted in an increase in the risk estimate of social support by co-workers. This may imply that the effect of social support is different for employees with high and low exposure to physical risk factors. Additional analyses indeed showed that the effect of social support of co-workers was higher when the physical load was high. The fact that many studies also report a positive association between work related psychosocial factors and neck and upper limb symptoms after adjustment for physical load leaves room for additional explanations. In a similar manner an intermediate role of an increase in work stress can be hypothesized: high job demands lead to stress symptoms, after which stress symptoms lead to physiological responses that enhance the development of musculoskeletal symptoms. This explanation is supported by the fact that adjustment for stress symptoms in the multivariate analyses in the study of Van den Heuvel et al. [112], resulted in a decrease of the relative risk of high job demands. Nevertheless, the relative risks of high job demands were still considerable after the inclusion of stress symptoms, indicating that the role of high job demands in the aetiology of neck and upper limb symptoms is partly but not fully mediated by the stress symptoms they might cause.
290 J Occup Rehabil (2006) 16:279 302 It is also generally accepted that musculoskeletal pain can be experienced in the absence of evident physiological change or tissue damage and that such pain is modulated primarily by cognitive processes [83]. For example, when job demands are high symptoms may be reported which may have gone unnoticed in a less demanding work environment. This effect may influence the relationship between job demands and neck and upper limb symptoms. Apart from work demands, personal factors, like personality traits, or the combination of demands from work and demands from private life, could contribute to the development of stress and thus also contribute to musculoskeletal symptoms. The study of Van den Heuvel [114] and the study of Nicholas et al. [84], both showed that the association between workrelated exposure, such as high job demands and prolonged VDU-work with neck and upper limb symptoms was partly mediated by a high risk work style. In addition Van den Heuvel [114] showed an association of a high-risk workstyle with overcommitment, as well as an association of overcommitment with neck and upper limb symptoms. The fact that the association of overcommitment and neck and upper limb symptoms decreased after adjustment for the workstyle scales, in particular for the scales working through pain and social reactivity, suggests that the effect of overcommitment is largely mediated by workstyle. The study suggests that 34% of the effect of prolonged VDU-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 the workstyle factor working through pain, and the cross sectional nature of the study the results should be drawn with care. Many laboratory studies of psychosocial stress have illustrated that the internal biomechanical load may increase with simulated work environmental stressors [20, 35, 62, 124], even when the intensity of the external exposure is kept constant or is reduced [122]. These studies clearly underline the effect of increased muscle force production in conditions of psychosocial stress. Increased muscle activity due to stress may hamper relaxation of the muscle fibers during (micro) pauses. In the Cinderella hypothesis of Goran Hagg work related stress may therefore take the role of the wicked sisters that keep the small motor units working even during breaks. Stress may also lead to increased and sustained muscle forces due to inadequate unwinding [68] and altered movement patterns [119]. Seen from a more pathophysiological perspective, stress may, apart from an increased muscle activity, impair circulation and the supply of oxygen to tissues as a result of hyperventilation. Moreover, prolonged stress may degrade tissue quality and the ability of tissues to recover due to hormonal processes [123]. Responsiveness to psychosocial stressors may differ greatly between subjects. Individual factors such as gender, personality type, and trait anxiety appear to have an influence on this responsiveness [19, 75, 119]. Conclusions 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. Most of these studies analysed the effect of high demands, low control and poor support at work on symptoms or signs of neck and upper limb. 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. In most studies only one of the factors is modestly related to these symptoms. The combination of high demands and low control at work i.e. high strain seems to have more impact on neck shoulder symptoms than on symptoms in arm or wrist. Perceived stress was not studied in as many studies, yet more consistently related to these neck and upper limb symptoms. This also applies to general distress or other pain (co-morbidity).
J Occup Rehabil (2006) 16:279 302 291 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 aetiology of neck and upper limb symptoms. However, studies concerning these factors are promising but too scarce to draw conclusions. Future studies should address these behavioural aspects. Part II: Effective interventions Introduction If work related neck and upper limb disorders are to be prevented or dealt with, employers and employees need to know which approach is effective. However, empirical support of the effectiveness of measures aimed at prevention of work related neck and upper limb symptoms and sick leave is largely absent. Interventions should be targeted to the risk factors that have a strong effect on reduction of neck and upper limb symptoms and are prevalent, i.e. with a large attributable fraction. Interventions aimed at reducing sick leave and enhancing return to work should be focussed on the main prognostic factors and obstacles for work resumption. Since perceived stress is one of the risk factors identified for work related upper limb symptoms, interventions available to prevent (the adverse health effects) of occupational stress may also have an effect on prevention of neck and upper limb symptoms. These occupational stress interventions focus on either the individual, the organisation or the individual-organisational interface [95]. This is in line with the factors presented in the model in Fig. 2. These factors are the work-organisation (including culture and values), the job/task-related psychosocial risk factors, workstyle, workstress and individual characteristics such as overcommitment, coping and cognitions. Interventions may also be classified as being primary, secondary or tertiary in nature, each serving different purposes [53]. Primary organisational interventions are either at a company, job or task level. Examples are interventions aimed at job enrichment and task rotation. Individual interventions focus on improving skills, work style, relaxation, biofeedback, cognitive training, and individual counselling etc. Individual interventions most likely are more effective, particularly on the long term, when also structural changes in the work have taken place [70, 109]. Most secondary or tertiary interventions also focus on individual psychosocial risk factors such as predispositions (attitudes or beliefs), emotional reactions (fear or distress), or relational factors (conflict or lack of support). Few secondary or tertiary interventions target work organisational psychosocial risk factors e.g. job stress, social support or conflicts in the workplace in order to enhance return to work [105]. Interventions targeted at the work organization often have an impact on both the physical and psychosocial load of the workers. In many cases the individual interventions also affect both the external or internal mental and physical load. The division between primary, secondary and tertiary preventions in case of work related neck and upper limb problems with their recurrent and episodic nature is often not very clear cut since most primary interventions also focus on those with early symptoms without work loss and secondary preventions often include return to work programmes after short spells of sick leave etc. We therefore group the interventions in two groups primary/secondary and secondary/tertiary. Pransky and Robertson [92] published a paper on the implications of the relationship between stress and work related upper extremity disorders for prevention and management. For studies before 2000 we relied on that review. A literature search was undertaken to identify studies published after this date.
292 J Occup Rehabil (2006) 16:279 302 In accordance with the model in Fig. 2 and the division of Semmer, Kompier and Kristensen we classified the literature on effectiveness of reduction of neck and upper limb symptoms by interventions in the following categories: a. Primary/secondary interventions aimed at the work organisation b. Primary/secondary interventions aimed at the individual c. Primary/secondary interventions combining different approaches d. Secondary/tertiary interventions aimed at the work organisation f. Secondary/tertiary interventions aimed at the individual Primary interventions aimed at the work organisation We will discuss the effect of implementing different work-rest schedules as a work organisational intervention. These interventions may be seen as changing the work (organisation) but they also aim at changing individual behaviour or work style. Evaluations of organisation-level interventions are relatively scarce, because a methodologically sound evaluation of this type of intervention is difficult. In a meta-analysis Van der Klink et al. [115] determined the effectiveness of four types of occupational stress-reducing interventions: cognitive behavioural approaches, relaxation techniques, multi-modal interventions and organization-focused interventions. Van der Klink et al. [115] reported a small and non significant effect size for the (few) organisational interventions that were studied with regard to psychological responses and resources in controlled studies. Uncontrolled trials and case reports have been more positive. Murphy and Sauter [81] also concluded in their summary of the effectiveness of work organization interventions that there is untill now little ground for enthusiasm concerning the success of these type of interventions. Interventions for task rotation or task enrichment Five studies addressed the effectiveness of task rotation and task enrichment in repetitive or computerwork. In a study by Christmansson et al. [15] tasks were added to highly repetitive assembly work. This study reported favourable changes in autonomy, and task variation, but an increase in the prevalence of upper extremity disorders. Aborg and colleagues [1] studied office workers engaged in task rotation, which should have redistributed repetitive computer work over the day. However, as a result, the periods of computer use without a break increased, by a decrease in total time spent on the computer. No positive effects on upper extremity disorders was observed. Female cashiers in the study by Rissén and colleagues [94] had to perform other work tasks besides cashier work, resulting in a decrease of the total duration of cashier work by 60%. The remaining work time was spent filling shelves and helping at other departments of the store. No positive effect on upper extremity disorders was observed. Finally, Kuijer and colleagues [58] studied refute collectors who applied task rotation by switching between refuse collection and driving the truck. No effect on upper extremity problems was observed. In general, these studies showed limited methodological quality. None of the studies were randomised and only two had a control group. In addition, not all studies checked whether the relevant exposures actually changed after implementation of task rotation or task enrichments. In conclusion there is no conclusive evidence for a positive effect of task rotation and task enrichment on upper extremity problems. Work-rest schedules Three studies investigated the effect of a change in work-rest time schedules. Wergeland and colleagues [126] showedthatashorteningoftheworkdayfrom8to6hperday,was
J Occup Rehabil (2006) 16:279 302 293 associated with a lower prevalence of upper extremity disorders among hospital workers. Dababneh and colleagues [18] did not find a positive effect of added breaks among workers in a meat processing plant. Van den Heuvel and colleagues [110] evaluated the introduction of rest break software among computerworkers with starting upper limb symptoms in a RCT. This did not result in reduction of the symptoms, although the respondents themselves were satisfied with the program and self-reported recovery was higher in the intervention groups. Moreover, productivity, expressed as the number of key strokes, was statistically significantly higher in the intervention group. However, no data on keystroke usage were available for the period before the intervention. In addition to these field studies, six lab studies tested the short term effects of added breaks on discomfort in the upper extremity. In one study, subjects had to perform a repetitive industrial task [76]. The findings revealed that discomfort in the shoulder region increased, but that additional breaks did not have an effect on the rise of discomfort during the workday. In the other five lab studies, subjects had to perform computer tasks (mainly data-entry). Three of these studies found an effect of added breaks on reduction of discomfort [6, 31, 77]. The studies by Karwowski and colleagues [50], and Henning and colleagues [39] did not show a positive effect of added breaks. In conclusion, high quality field studies are needed to reach a more definite conclusion on the effectiveness of added rest breaks. For now, inconclusive evidence is concluded. Management engagement In the studies of Linton [66] managers were trained to cope with and effectively reduce workplace stressors. These studies show positive effects on reduction of workplace stressors, stress related response and self reported musculoskeletal complaints. Recently, Eklof and Hagberg [24], tested whether feedback and discussion of ergonomics and the psychosocial working environment with individuals, groups or supervisors among VDU workers in one session, effectively reduced musculoskeletal symptoms in a cluster randomised trial. However, no reduction in musculoskeletal symptoms was found, only social support increased in the group with feedback by the supervisor. The older studies suggest that training or involvement of management seems promising in reduction of stress related responses and work related neck and upper limb problems. The training should be more intense than one session. Primary interventions aimed at the individual Workstyle/work techniques Interventions aimed at relaxation i.e. myofeedback can also be seen as measures intervening in psychosocial and physical load. Van der Klink et al. [115] found a small positive effect of both psychological and physical relaxation techniques on quality of work, psychological responses and resources, physiology and anxiety symptoms. Faucett and colleagues [25] studied the effect of muscle training in an RCT involving EMG biofeedback among healthy workers performing a complex assembly task. The second intervention group received educational training involving stress management and problemsolving skills. After 6 weeks of follow-up fewer symptoms were observed in the muscle learning group and the educational group, compared to the control group. Despite further lowering of muscle tension during the consecutive period in the muscle learning group, after 32 weeks, no difference between symptom prevalences were observed between the three groups.
294 J Occup Rehabil (2006) 16:279 302 Peper and colleagues [89], showed in a pilot study among computer users, that an intervention focused on a healthy workstyle (such as taking breaks), showed significant effects in reduction of upper extremity symptoms, as well as break taking behaviour, healthy breathing patterns and ergonomics. These results are promising for short term effects, but extending this to long term effects needs more attention. Cognitive approach Cognitive-behavioural approaches aim at changing cognitions and subsequently reinforcing active coping skills [115]. In their meta-analysis these interventions proved to be more effective than relaxation techniques, multi-modal programs and organization focused programs. Cognitive behavioural interventions especially helped to improve perceived quality of work life and psychological responses and resources. They also significantly reduced anxiety symptoms. It is suggested that employees with high job control profit more from being provided with individual coping skills than employees working in more constrained environments, because this high job control allows them to exercise these coping skills. Cognitive training, consisting of group training and discussions, was evaluated in the third arm of the randomised controlled trial cited above among workers who performed complex assembly tasks [25]. After six weeks, a favourable effect was found on symptoms of the upper extremities. Evaluation of the effect of a cognitive approach to reduce neck and upper limb symproms deserves more attention. Primary interventions combining different approaches In industrial environments, multiple ergonomic interventions, or a combination of ergonomic equipment, organizational changes and training courses, are often introduced and evaluated simultaneously for the same workers. Lincoln [65] concluded, that multiple component interventions that included for instance workstation redesign, establishment of an ergonomics task force, job rotation, ergonomics training, and restricted duty provisions, were associated with reduced incidence rates of carpal tunnel syndrome. However, the results were inconclusive because they did not adequately control for potential confounders. Parenmark et al. [86] conducted such a multiple component preventive intervention programme for conveyor belt workers, including training to reduce shoulder stress, a participative redesign of working methods and changes to performance bonuses and compared the effect with a different site where no intervention had taken place. The authors attribute the positive results, such as a 20% drop in sickness absence, to various factors, including awareness of the need to avoid high muscle stress. In addition, Feuerstein and colleagues [27] evaluated in a controlled study an intervention focusing both on job stress management and ergonomics. They found a significant decrease in symptoms and limitations. However, the job stress management component did not enhance the outcomes of the ergonomics program. It should be noted that the ergonomic intervention was compared to the ergonomic plus job stress management intervention (no neutral control group). The above studies show positive and negative results in different work environments. Therefor there is inconclusive evidence on the effect of these combined approaches.
J Occup Rehabil (2006) 16:279 302 295 Secondary/tertiary interventions aimed at the work organisation Recently several randomised trials have been published that show that work adjustments including improvement of the work organisation are beneficial for early return to work after sub acute low back pain [5, 69]. Pransky et al. [91] reported that employer attitudes toward work disability might also impact return to work outcomes. Van Duijn et al. [117] reported the results of a survey of occupational health physicians and human resources managers showing that lack of coworker support for modified work re-entry programs was perceived as a major obstacle to successful return to work. Based on a review of the literature, Teasell and Bombardier [107] reported that lack of availability of modified work and lack of autonomy in the workplace were predictors of prolonged work disability. These findings underscore the role of psychosocial work conditions, in explaining a worker s return to work. However, none of these findings concern return to work after neck and upper limb disorders. Katz et al. [51] concluded that work place interventions that address organizational culture can be useful in reducing sick leave after carpal tunnel syndrome. Gimeno et al. [32] present, based on the same study, that a job with high demands and low control (high strain) predicted not returning to work after CTS or returning to work but not successfully meeting job demands, at six months. From these results it is clear that work related psychosocial factors such as work organisation and attitudes of management may be important for effective return to work but too few studies deal with these factors after return to work due to neck and upper limb problems. Secondary/tertiary interventions aimed at the individual Several reviews have addressed the role of individual psychosocial factors in the development of prolonged pain and disability [33, 90, 104]. However only few of these studies concerned the prognosis of neck and upper limb problems. Mainly based on studies of prognosis of low back pain it is believed that factors such as high levels of pain catastrophizing, pain related fear, poor problem solving abilities, low expectancies about the probability of returning to work, attitudes toward work re-entry, motivation and lack of confidence in the ability to perform work-related activities are associated with more prolonged work absence [103, 105]. Therefore several interventions are designed to target these factors in preventions of prolonged musculoskeletal pain or disability but again few of these studies focus on neck and upper limb problems. A recent systematic review on effective return to work treatment programmes for sick listed patients with non-specific musculoskeletal complaints concluded for instance that there was no RCT that concerns return to work after non specific upper limb problems [78]. The term cognitive-behavioural does not refer to a specific intervention, but rather to a class of intervention strategies that might include self-instruction (e.g., motivational self-talk), relaxation or biofeedback, developing coping strategies (e.g., distraction, imagery), increasing assertiveness, minimizing negative or self-defeating thoughts, changing maladaptive beliefs about pain, and goal setting [105]. Many of the cognitive-behavioural programmes are combined with other interventions in a multidisciplinary programme. These programmes often include both physical reconditioning and a behaviour-oriented approach with emphasis on i.e. coping (problem-solving ability), fear of movement and personality factors such as the individual s own responsibility. The programmes vary considerably in intensity. Five fairly old studies investigated a form of behavioural treatment, all using a group of people on a waiting list as a control group [12, 80, 100 102, 106] and recovery or reduction of neck and upper limb symptoms as the outcome measure. In most cases the behavioural