Documents methodology 926 results

"In 2008 it was decided by the Nordic Working Environment Committee under the Nordic Council of Ministers that an overview was needed on fatal occupational accidents in the Nordic countries. A selected group from agencies in all the Nordic countries maintaining the occupational accident registries was formed. It should provide a report that would give a review of systems involved concerning occupational accidents, i.e. the reporting process, the investigation process, the registration process, the registries and legal statutes. On the basis of this the numbers of fatal occupational accidents in the Nordic countries during the time period 2003 to 2008 would be studied.

The comparison between the Nordic countries concerning the systems showed relatively minor differences. However, as these small differences involve all or nearly all aspects of the system process in occupational accidents, comparison of occupational accidents in the Nordic countries should be approached with care.

The total number of fatal occupational accidents in the time period was 1243. That is between 1.51 to 2.49 fatal occupational accidents per 100,000 workers per year, varying between countries. Over 93% of these accidents involved males. This no doubt reflects the predominance of men in the most dangerous branches, i.e. agriculture, construction, and transport and communication. This is in accordance with that “land vehicles” are the leading material agent involved, and that the leading factor going wrong is loss of control, breaking or bursting of material agent and falls.

In order to make data on occupational accidents more comparable a closer collaboration between the Nordic countries, in the field of occupational accident investigation and registration, is called for. This would make the database for the battle against fatal occupational accidents and occupational accidents in the Nordic countries more effective and improve our common ability to identify prevention strategies."

"This study aimed at developing a model for determining the work-relatedness of low-back pain for a worker with low-back pain using both a personal exposure profile for well-established risk factors and the probability of low-back pain if the worker were unexposed to these factors.The model is the first that estimates the probability of work-relatedness for low-back pain for a given worker with low-back pain seen by a general practitioner or an occupational health physician."

Various conservative treatment options for repetitive strain injury are widely used, despite questionable evidence of their effectiveness. This systematic review evaluates the effectiveness of these treatment options for relieving symptoms of repetitive strain injury and improving activities of daily living. Searches in Medline and Embase, with additional reference checking resulted in 15 eligible trials for this review. Methodological quality was assessed, and data-extraction was performed. With the use of a "best-evidence synthesis", no strong evidence was found for the effectiveness of any of the treatment options. There is limited evidence that multidisciplinary rehabilitation, ergonomic intervention measures, exercises, and spinal manipulation combined with soft tissue therapy are effective in providing symptom relief or improving activities of daily living. There is conflicting evidence for the effectiveness of behavioral therapy. In conclusion, little is known about the effectiveness of conservative treatment options for repetitive strain injury. To establish strong evidence, more high-quality trials are needed.

The systematic review by Konijnenberg et al (1) in this issue of the Scandinavian Journal of Work Environment & Health deals with conservative treatment methods for the great problem of neck and upper-limb disorders in working populations. Fifteen randomized controlled trials (RCT) or controlled clinical trials (CCT) fulfilled the inclusion criteria of the review. Five of these scored 6/12 or higher according to their internal validity criteria and were considered high-quality studies. In the presence of a wide range of treatments, no treatment modality could be evaluated on the basis of a remarkable number of high-quality studies. There was, however, limited evidence in favor of physiotherapy, exercises, and ergonomic improvements. Repetitive strain injury (RSI) is a loose concept used in this review broadly to encompass a range of disorders from the neck and thoracic spinal area to the fingertip. In principle, outcomes in treatment or intervention studies should be based on symptoms or findings or both independently of the etiologic factors of the disease, and we should avoid concepts that include the assumed etiologic factor. To me, "neck and upper-limb disorders in working populations" would have seemed to be a more appropriate concept, especially since the work-relatedness of the conditions is difficult to assess; in fact it was not even addressed in some of the studies reviewed. Moreover, the requirement of work-relatedness resulted in the exclusion of some potentially high-quality studies (2) that did not have "work-relatedness" as an inclusion criterion, but still probably dealt with a largely similar group of disorders. For instance, in the study of Taimela et al (2), one inclusion criterion was the possession of a permanent job. But if we accept the concept of repetitive strain injury and assume that repetitive movements are one of the major causes of this strain, would not then modification of exposure (or engineering control) be a natural component in a treatment aimed to enhance recovery and prevent recurrence? Many of us would probably say yes, but a look at the tables in the review shows that only very few studies had workplace adjustment as a treatment or as one constituent in the treatment protocol. Another conspicuous feature of this review and also of some other related recent reviews (for an example, see reference 3) is that ergonomic intervention has usually been carried out in the office environment. While there is no doubt that office workers do have work-related musculoskeletal problems, such problems are even more frequent in the construction, transportation, and manufacturing industries and in some branches of the service sector, for example, hospital, kitchen, and cleaning work (4). Hopefully, the target workplaces for future workplace intervention studies will be determined by the size and seriousness of the problems and not only by the feasibility of carrying out an intervention study, such as stationary work in an office environment versus a changing work environment at a construction site, or the marketing of new input devices or computers. The magnitude or the duration of the treatment effects did not deserve much attention in this review, which is understandable since high-quality studies were few in number. However, a look at the high-quality studies shows that a modest reduction in pain was typical, and this effect was no longer present in the later phases of follow-up. Cost-effectiveness aspects were not considered in any of the studies included in this review. The relatively meager results in most studies do not suggest that the treatments were cost-effective in general. Many risk factors contribute to the occurrence of neck and upper-limb disorders among working populations (5, 6, 7). In a multifactorial condition, it is unlikely that a single measure would result in significant relief, something that is suggested by the meager results in several studies accepted for review. With regard to the etiology of most neck and upper-limb disorders, multidisciplinary approaches should have a higher potential. Unfortunately, multidisciplinary rehabilitation had been tried in only one controlled clinical trial, which received a very low score. The authors are correct in being worried about the use of multiple outcomes in intervention studies, the result being a high likelihood that a positive result is obtained by one of the outcomes by chance. Researchers should be more critical in the design of their studies. They should select only the most relevant outcome measures and restrict the outcomes only to them. Most studies relied solely on subjective outcome parameters, since few generally accepted objective methods exist. This is a major scientific problem, especially since blinding subjects for treatment is hardly possible. A major question of treatment policy in relation to neck and upper-limb disorders among working populations is whether the focus should be on treating the individual or his or her environment, especially in the control of workload. Trying to get an answer from workplace intervention studies, especially randomized controlled trials, involves an inherent potential of bias. As it is much easier to randomize individuals into different physical therapies, exercise or other treatment modalities, than it is to randomize workstations to be changed or not, there will always be more randomized controlled trials with treatments directed toward the individual. Therefore, there are greater chances of obtaining positive results from such treatments at the cost of engineering controls. Moreover, the current instability at workplaces, with high turnover rates and frequent reorganizations, makes it increasingly difficult to carry out workplace intervention studies successfully. It is easy to share the authors' worry about the absence of high-quality studies as evidence for the effect of most currently used treatment modalities. As the authors say, there is a higher possibility of bias, for example, an erroneous positive result of a treatment, in a low-quality study than in one of high-quality. This issue was systematically addressed in a review on acupuncture trials involving chronic neck and back pain (8), in which the authors were able to show that the most valid trials tended to have negative results. Konijnenberg and his collaborators' review shows convincingly that the scientific basis for current treatment practices with respect to neck and upper-limb disorders in working populations is limited and based largely on low-quality studies. More high-quality studies are definitely needed. Moreover, research priorities should not be restricted to groups of workers and treatment modalities that are easy to study. Instead, studies should be undertaken on treatment modalities that carry a potential to be efficacious. Worker groups with the highest risk of neck and upper-limb disorders should be the focus. Such studies are often laborious and should therefore be supported by sufficient funding. It is possible that new knowledge from such studies may change our understanding of the efficacy of some treatments and, therefore, create pressure to change current treatment practices. What should the practitioner do now while we are still waiting for the results of such studies? The Panel on Musculoskeletal Disorders established by the National Research Council and the Institute of Medicine concluded in their review that the epidemiologic evidence for upper-extremity disorders supports the important role of physical load factors (7). Based on this evidence, primary and secondary intervention at the workplace, including engineering and administrative controls, was recommended. As there are still few prospective studies on incident neck and upper-limb disorders, it is difficult, on the basis of epidemiologic studies, to estimate the relative potential of these measures in primary versus secondary prevention.

"Objectives The present study was designed to test the demand-control model using indicators of both health impairment and active learning or motivation.Methods A total of 381 insurance company employees participated in the study. Discriminant analysis was used to examine the relationship between job demands and job control on one hand and health impairment and active learning on the other.Results The amount of demands and control could be predicted on the basis of employees' perceived health impairment (exhaustion and health complaints) and active learning (engagement and commitment). Each of the four combinations of demand and control differentially affected the perception of strain or active learning. Job demands were the most clearly related to health impairment, whereas job control was the most clearly associated with active learning. Conclusions These findings partly contradict the demand-control model, especially with respect to the validity of the interaction between demand and control. Job demands and job control seem to initiate two essentially independent processes, and this occurrence is consistent with the recently proposed job demands-resources model."

Objectives The purpose of this study was to develop and validate a sampling strategy for characterizing the finger force exposures associated with computer mouse use. Methods Mouse forces were measured from 16 subjects (8 men, 8 women), on 3 separate days, at their actual workstations while they performed (i) their regular work, (ii) a battery of standardized tasks, and (iii) simulated mouse use. Results The forces applied to the mouse did not vary between hours or days. During regular work, the mouse was used 78.0 (SD 40.7) times per hour, accounting for 23.7 (SD 9.5)% of the worktime. The mean forces applied to the sides and button of the mouse were low, averaging 0.6 % of the maximal voluntary contraction (%MVC) (0.43 N) and 0.8 % MVC (0.35 N), respectively. The forces applied to the mouse during the standardized tasks differed from the regular work forces; however, there were moderate-to-strong correlations between the 2 measures. Conclusions With respect to performing exposure assessment studies, the 3 major findings were (i) mouse force measurements should be made while subjects perform their actual work in order to characterize the absolute applied force accurately, (ii) the forces applied to the mouse during the performance of a short battery of standardized tasks can be used to characterize relative exposure and identify computer operators or work situations for which higher forces are applied to the mouse, and (iii) subjects cannot accurately simulate mouse forces.

For years scientists have kept saying that elevated postures of the arm are a risk factor for shoulder disorders, but it is not known how much elevation and for how long is too much (1). Others have called for more precision in exposure assessment in epidemiologic studies, emphasizing the importance of the intensity, frequency, and duration of exposures (2). The article by Punnett and her co-workers (3) on shoulder disorders in this issue of the Scandinavian Journal of Work, Environment & Health is important for practitioners and scientists in occupational health and ergonomics, and also for others involved in the prevention of musculoskeletal disorders. This study found a dose-response relationship between the duration of severe shoulder flexion or abduction as a proportion of cycle time and shoulder disorders. The risk was clearly increased for severe shoulder flexion or abduction (>90 degrees) for less than 10% of the cycle time, and it increased when the proportional duration was 10% or more. The authors made considerable effort to assess also forces imposed on the shoulder joint and used a biomechanical model to incorporate posture and hand loads into a common metric of force. They failed, however, to show an elevated risk for force, probably because the worktasks used in this study did not involve the exertion of high forces. The repetition rate of arm movements was also observed. But it correlated strongly with shoulder elevation, and its effects could not therefore be distinguished. The strength of this study is its objective assessment of its outcome and exposure. Not all the cases had positive clinical findings, but the risk estimates were slightly higher for those with clinical findings, and the results therefore suggested an even stronger association between clinically manifest disease and postural load. The exposure assessment included the intensity, frequency, and duration of shoulder postures and resulted in a multitude of data that required careful data reduction and analysis. The history of epidemiologic studies on shoulder disorders is short, not really starting until some 20 years ago, when a group of studies on shipyard welders was published that showed a high prevalence of shoulder disorders (4). Overhead welding was considered the main work-related factor. Later, studies among bricklayers and rockblasters showed an association between acromioclavicular arthrosis and cumulative exposure to physical loads, such as the sum of lifted tonnes during worklife (5). In the same group of workers, shoulder tendinitis was associated with cumulative vibration dose (6). A recent study found the prevalence of shoulder impingement syndrome to be higher among current and former slaughterhouse workers than in a comparison group. Video recordings of a group of the slaughterhouse workers showed that they spent half of their worktime with arm elevation of ?30 degrees (7). There are no prospective studies on clinically defined shoulder disorders. The study by Punnett and her co-workers seems to be among the most rigorous available on the association between shoulder disorders and physical workload factors. The results will be useful in the primary and secondary prevention of shoulder disorders. For monotask jobs, the results can be considered a source of reference values for the proportional duration of overhead work. The proportional durations can also be translated into minutes or hours of shoulder flexion or abduction per day. As there are very few similar data with which to compare the results of Punnett and her co-workers' study, it is obvious that more studies are needed. At this point we can also question how much further epidemiologic studies will take us. We could probably learn more about, for example, hand loads or forces imposed on the shoulder joint with a worker population that is exposed to a wider range of forces. Other types of tasks could give us more information about the repetition rates of shoulder movements. Such studies as this one bring us to the contact surface between epidemiologic and experimental research; more information on shoulder postures, hand loads, arm movement frequencies, and their combinations can be obtained largely in the laboratory. But, as we all know, we are unlikely to have a clinically relevant health outcome in the laboratory. Reference values can then be subjected to further reasoning by collecting the best available epidemiologic and experimental data and looking for patterns of dose-response between exposures and outcomes and interactions between exposures.

"The electromyographic (EMG) activity of shoulder and forearm muscles was recorded during a standardized computer task with different combinations of time pressure, precision demands, and mental demands to study the interaction of these factors and their effect on muscular response during simulated computer work. The interaction between work pace and other exposure factors must be taken into account when the effects of changes in exposure demands on muscular response are predicted. Only then can it be predicted whether changing demands will constitute a risk of developing musculoskeletal disorders."