Work-related musculoskeletal disorders: the epidemiologic evidence and the debate.

The debate about work-relatedness of musculoskeletal disorders (MSDs) reflects both confusion about epidemiologic principles and gaps in the scientific literature. The physical ergonomic features of work frequently cited as risk factors for MSDs include rapid work pace and repetitive motion, forceful exertions, non-neutral body postures, and vibration. However, some still dispute the importance of these factors, especially relative to non-occupational causes. This paper addresses the controversy with reference to a major report recently commissioned by the US Congress from the National Research Council (NRC) and Institute of Medicine (IOM) (2001). The available epidemiologic evidence is substantial, but will benefit from more longitudinal data to better evaluate gaps in knowledge concerning latency of effect, natural history, prognosis, and potential for selection bias in the form of the healthy worker effect. While objective measures may be especially useful in establishing a more secure diagnosis, subjective measures better capture patient impact. Examination techniques still do not exist that can serve as a "gold standard" for many of the symptoms that are commonly reported in workplace studies. Finally, exposure assessment has too often been limited to crude indicators, such as job title. Worker self-report, investigator observation, and direct measurement each add to understanding but the lack of standardized exposure metrics limits ability to compare findings among studies. Despite these challenges, the epidemiologic literature on work-related MSDs-in combination with extensive laboratory evidence of pathomechanisms related to work stressors-is convincing to most. The NRC/IOM report concluded, and other reviewers internationally have concurred, that the etiologic importance of occupational ergonomic stressors for the occurrence of MSDs of the low back and upper extremities has been demonstrated.     

Ligaments: a source of work-related musculoskeletal disorders.

The mechanical and neurological properties of ligaments are reviewed and updated with recent development from the perspective which evaluates their role as a source of neuromusculoskeletal disorders resulting from exposure to occupational activities. Creep, tension-relaxation, hysteresis, sensitivity to strain rate and strain/load frequency were shown to result not only in mechanical functional degradation but also in the development of sensory-motor disorders with short- and long-term implication on function and disability. The recently exposed relationships between collagen fibers, applied mechanical stimuli, tissue microdamage, acute and chronic inflammation and neuromuscular disorders is delineated with special reference to occupational stressors.     

Cassava in South America, Brazil's contribution and the lesson to be learned from India

South America is responsible for about half of the cassava world production. In the 1970's productivity of the crop on the continent was about 15 ton/ha, and dropped continuously until reaching 12 ton/ha in 2004. India's productivity of cassava increased from 10 ton/ha in the 1970's to 28 ton/ha in 2004. Brazil contributed significantly to improving cassava crops through the Instituto Agron?mico de Campinas in the 1960's and 1970's. The Universidade de Brasília released high-protein content hybrids, apomictic clones and explored the potential of indigenous landraces.     

The change of working posture in Manggur decreases cardiovascular load and musculoskeletal complaints among Balinese gamelan craftsmen

Manggur, which means to plane down or sharpen, is a manual process in producing copper blades of Balinese gamelan orchestra. The craftsmen of Manggur work 6 to 8 hours a day, sitting on the floor with folded legs and hunched back. Because the craftsmen often complain about musculoskeletal problems after having completed a full day work, an ergonomic intervention was made by changing their usual working posture (the first working posture) into working on tables while sitting on chairs for one hour and alternately standing for half an hour (the second working posture). Treatment by subject design was applied to 22 randomly chosen craftsmen. Resting heart rate and working heart rate were measured by using a stopwatch, and the number of musculoskeletal complaints were recorded with Nordic Body Map Questionnaire. As a result, the second working posture caused significant reductions in working heart rate, work pulse (the difference between working heart rate and resting heart rate) and the number of musculoskeletal complaints. These results suggest that the change of working posture in manggur decreases cardiovascular load and musculoskeletal strain among Balinese gamelan craftsmen.     

Individual factors and musculoskeletal disorders: a framework for their consideration.

Individual factors have been variously defined as non-work, demographic, physiological or psychological factors. They may represent a variety of important constructs at different relevant levels that may not be initially evident in their measurement. These include: work-related factors e.g., job assignment, duration of exposure, work style, anthropometric mismatches, and differential responses to job demands; concomitant external or internal exposures e.g., sports, smoking, and endogenous hormones; and physical, psychological and social vulnerabilities e.g., prior injury, depression, socio-economic status. Such factors operate in different ways in the development, course and response to interventions of musculoskeletal disorders. Newer framings of their contribution to musculoskeletal disorders are providing new insights into the role of such factors as some among many which contribute to the burden of MSK disorders in working age populations. As researchers, practitioners and policy makers, we need to consider them in order to reduce burden, to protect the vulnerable and to match interventions to different groups of people most appropriately.     

Salt handling in the distal nephron: lessons learned from inherited human disorders

The molecular basis of inherited salt-losing tubular disorders with secondary hypokalemia has become much clearer in the past two decades. Two distinct segments along the nephron turned out to be affected, the thick ascending limb of Henle's loop and the distal convoluted tubule, accounting for two major clinical phenotypes, hyperprostaglandin E syndrome and Bartter-Gitelman syndrome. To date, inactivating mutations have been detected in six different genes encoding for proteins involved in renal transepithelial salt transport. Careful examination of genetically defined patients ("human knockouts") allowed us to determine the individual role of a specific protein and its contribution to the overall process of renal salt reabsorption. The recent generation of several genetically engineered mouse models that are deficient in orthologous genes further enabled us to compare the human phenotype with the animal models, revealing some unexpected interspecies differences. As the first line treatment in hyperprostaglandin E syndrome includes cyclooxygenase inhibitors, we propose some hypotheses about the mysterious role of PGE(2) in the etiology of renal salt-losing disorders.     

Digital transformation: The role of computer use in employee health

This paper studies employee health in the context of digital transformation in Germany. While most studies have focused on mental health, we focus on physical health. Using pooled survey data, we estimate how an increased use of computers in the workplace relates to subjective health and work-related health complaints. We find that employees using the computer frequently report better subjective health and a significantly lower prevalence of back pain and physical exhaustion. After controlling for physical work exposures, the health-promoting effect of computer use is much smaller, suggesting that high computer use is associated with a less physically demanding work environment, which in turn relates to better (physical) health outcomes. While digital transformation seems to foster physical health, there are hints that mental health could deteriorate. Thus, the focus of occupational health is shifting towards the prevention of mental stress.     

Small extracellular vesicles from mesenchymal stromal cells: the next therapeutic paradigm for musculoskeletal disorders

Musculoskeletal disorders are one of the biggest contributors to morbidity and place an enormous burden on the health care system in an aging population. Owing to their immunomodulatory and regenerative properties, mesenchymal stromal/stem cells (MSCs) have demonstrated therapeutic efficacy for treatment of a wide variety of conditions, including musculoskeletal disorders. Although MSCs were originally thought to differentiate and replace injured/diseased tissues, it is now accepted that MSCs mediate tissue repair through secretion of trophic factors, particularly extracellular vesicles (EVs). Endowed with a diverse cargo of bioactive lipids, proteins, nucleic acids and metabolites, MSC-EVs have been shown to elicit diverse cellular responses and interact with many cell types needed in tissue repair. The present review aims to summarize the latest advances in the use of native MSC-EVs for musculoskeletal regeneration, examine the cargo molecules and mechanisms underlying their therapeutic effects, and discuss the progress and challenges in their translation to the clinic.     

Reducing the costs of work-related musculoskeletal disorders: targeting strategies to chronic disability cases.

Musculoskeletal disorders impose a significant direct cost burden on health care systems in the US and Canada and account for even greater indirect losses of productivity. The overall prevalence of musculoskeletal disorders is high, but a disproportionate share of costs is associated with a small number of cases with chronic pain. This is especially true for cases of occupational back pain, the single most common and costly musculoskeletal disorder in the workplace. A number of studies identify workplace characteristics associated with prolonged disability among cases of work-related back pain. These characteristics include: failure to receive job accommodations, receipt of disability benefit payments, and employment in high-risk industries or jobs that require heavy lifting. Research on the predictors of high-cost cases is limited, however, because of the lack of high-quality data and the need for a multidisciplinary approach. A new study, the Arizona State University Healthy Back Study, addresses some of these issues and promises new insights into effective strategies to reduce the proportion of high-cost claims.     

Sleep problems and computer use during work and leisure: Cross-sectional study among 7800 adults

Previous studies linked heavy computer use to disturbed sleep. This study investigates the association between computer use during work and leisure and sleep problems in working adults. From the 2010 round of the Danish Work Environment Cohort Study, currently employed wage earners on daytime schedule (N?=?7883) replied to the Bergen insomnia scale and questions on weekly duration of computer use. Results showed that sleep problems for three or more days per week (average of six questions) were experienced by 14.9% of the respondents. Logistic regression analyses, controlled for gender, age, physical and psychosocial work factors, lifestyle, chronic disease and mental health showed that computer use during leisure for 30 or more hours per week (reference 0–10 hours per week) was associated with increased odds of sleep problems (OR 1.83 [95% CI 1.06–3.17]). Computer use during work and shorter duration of computer use during leisure were not associated with sleep problems. In conclusion, excessive computer use during leisure – but not work – is associated with sleep problems in adults working on daytime schedule.     

Identifying shared genetic structure patterns among Pacific Northwest forest taxa: insights from use of visualization tools and computer simulations

Background

Identifying causal relationships in phylogeographic and landscape genetic investigations is notoriously difficult, but can be facilitated by use of multispecies comparisons.

Methodology/Principal Findings

We used data visualizations to identify common spatial patterns within single lineages of four taxa inhabiting Pacific Northwest forests (northern spotted owl: Strix occidentalis caurina; red tree vole: Arborimus longicaudus; southern torrent salamander: Rhyacotriton variegatus; and western white pine: Pinus monticola). Visualizations suggested that, despite occupying the same geographical region and habitats, species responded differently to prevailing historical processes. S. o. caurina and P. monticola demonstrated directional patterns of spatial genetic structure where genetic distances and diversity were greater in southern versus northern locales. A. longicaudus and R. variegatus displayed opposite patterns where genetic distances were greater in northern versus southern regions. Statistical analyses of directional patterns subsequently confirmed observations from visualizations. Based upon regional climatological history, we hypothesized that observed latitudinal patterns may have been produced by range expansions. Subsequent computer simulations confirmed that directional patterns can be produced by expansion events.

Conclusions/Significance

We discuss phylogeographic hypotheses regarding historical processes that may have produced observed patterns. Inferential methods used here may become increasingly powerful as detailed simulations of organisms and historical scenarios become plausible. We further suggest that inter-specific comparisons of historical patterns take place prior to drawing conclusions regarding effects of current anthropogenic change within landscapes.     

Inflammation reduces physiological tissue tolerance in the development of work-related musculoskeletal disorders.

Work-related musculoskeletal disorders (MSDs) cause substantial worker discomfort, disability and loss of productivity. Due to the difficulty in analyzing the tissues of patients in the early stages of work-related MSD, there is controversy concerning the pathomechanisms of the development of these disorders. The pathophysiology of work-related MSD can be studied more easily in animal models. The purpose of this review is to relate theories of the development of tissue injury due to repeated motion to findings of recent investigations in animals that address the role of the inflammatory response in propagating tissue injury and contributing to chronic or recurring tissue injury. These tissue effects are related to behavioral indicators of discomfort and movement dysfunction with the aim of clarifying key time points for specific intervention approaches. The results from animal models of MSD are discussed in the light of findings in patients, whose tissues are examined at a much later phase of MSD development. Finally, a conceptual model of the potentially negative impact of inflammation on tissue tolerance is proposed along with suggestions for future research directions.     

Introduction: microbiology and immunology: lessons learned from Salmonella.

Salmonella enterica, a Gram-negative bacterium, causes significant morbidity and mortality worldwide, and is an excellent model to study bacterial pathogenesis and cellular immune responses. With the development of powerful new technologies, there has been a fusion of research on immunology, molecular biology and cellular microbiology of S. enterica infections. This multidisciplinary research will enhance our understanding of the basic mechanisms of bacterial infections and immunity; it also provides new approaches towards therapeutic and control measures.     

Risk factors for neck and upper extremity disorders among computers users and the effect of interventions: an overview of systematic reviews

Background

To summarize systematic reviews that 1) assessed the evidence for causal relationships between computer work and the occurrence of carpal tunnel syndrome (CTS) or upper extremity musculoskeletal disorders (UEMSDs), or 2) reported on intervention studies among computer users/or office workers.

Methodology/Principal Findings

PubMed, Embase, CINAHL and Web of Science were searched for reviews published between 1999 and 2010. Additional publications were provided by content area experts. The primary author extracted all data using a purpose-built form, while two of the authors evaluated the quality of the reviews using recommended standard criteria from AMSTAR; disagreements were resolved by discussion. The quality of evidence syntheses in the included reviews was assessed qualitatively for each outcome and for the interventions.Altogether, 1,349 review titles were identified, 47 reviews were retrieved for full text relevance assessment, and 17 reviews were finally included as being relevant and of sufficient quality. The degrees of focus and rigorousness of these 17 reviews were highly variable. Three reviews on risk factors for carpal tunnel syndrome were rated moderate to high quality, 8 reviews on risk factors for UEMSDs ranged from low to moderate/high quality, and 6 reviews on intervention studies were of moderate to high quality. The quality of the evidence for computer use as a risk factor for CTS was insufficient, while the evidence for computer use and UEMSDs was moderate regarding pain complaints and limited for specific musculoskeletal disorders. From the reviews on intervention studies no strong evidence based recommendations could be given.

Conclusions/Significance

Computer use is associated with pain complaints, but it is still not very clear if this association is causal. The evidence for specific disorders or diseases is limited. No effective interventions have yet been documented.     

Alcohol use disorders (AUD) among tuberculosis patients: a study from Chennai, South India

Background

Alcohol Use Disorders (AUDs) among tuberculosis (TB) patients are associated with nonadherence and poor treatment outcomes. Studies from Tuberculosis Research Centre (TRC), Chennai have reported that alcoholism has been one of the major reasons for default and mortality in under the DOTS programme in South India. Hence, it is planned to conduct a study to estimate prevalence of alcohol use and AUDs among TB patients attending the corporation health centres in Chennai, India.

Methodology

This is a cross-sectional cohort study covering 10 corporation zones at Chennai and it included situational assessment followed by screening of TB patients by a WHO developed Alcohol Use Disorders Identification Test AUDIT scale. Four zones were randomly selected and all TB patients treated during July to September 2009 were screened with AUDIT scale for alcohol consumption.

Results

Out of 490 patients, 66% were males, 66% were 35 years and above, 57% were married, 58% were from the low monthly income group of 8. Age (>35 years), education (less educated), income (ConclusionsAUD among TB patients needs to be addressed urgently and the findings suggest the importance of integrating alcohol treatment into TB care.