The use of continuous exposure data for predicting CTS in fish processing operators

Carpal tunnel syndrome (CTS) remains one of the most commonly reported and studied work related musculoskeletal disorders. Categorical representations of exposures has been critical in identifying associations between risk factors and CTS, however, quantification of exposure—response relationships require using continuous exposure data. Also, few interactions between risk factors, especially between risk factor categories, have been investigated. The objectives of this study were to investigate the utility of using continuous exposure data and to identify interaction effects of risk factors, both within and between risk factor categories, for predicting CTS. A cross sectional study was performed at a fish processing facility in which 53 participants were evaluated during normal task performance. Due to task asymmetry, each hand was considered separately, providing 106 hands for analysis. Direct measurement and a questionnaire were used to quantify exposures to common occupational and personal risk factors. Stepwise logistic regression analysis was performed to identify three models for predicting CTS and assess predictive ability using: occupational risk factors only (three-way interactions considered), personal risk factors only (two-way interactions considered), and a mixed model considering two-way interactions across risk factor categories and previously identified significant interactions. Models including only occupational or personal risk factors were moderately accurate overall (73% and 77% respectively), but were not sensitive in differentiating between CTS cases and non-cases (39% and 33% respectively). The mixed model was found to be accurate (88%) and sensitive (78%), though only one interaction effect was included. The results of this study illustrate the importance of using continuous exposure data, especially in job tasks where exposures to occupational risk factors is similar, when differentiating between high and low risk job tasks.     

Effects of personal,psychosocial and occupational factors on low back pain severity in workers

Low back pain (LBP) remains the most common work-related musculoskeletal disorder (WMSD). While most of the LBP research has focused on occupational risk factors, other underlying causal mechanisms may exist since not all workers performing the same task develop an injury. Previous research has identified three primary risk factor categories for LBP (occupational, personal and psychosocial factors); however, few studies have investigated the impact of cross categorical risk factor interactions on LBP. The objective of this study was to investigate the effects of occupational, personal and psychosocial factors, and their interactions, on LBP severity in a population of workers currently suffering from LBP. Sixty LBP patients recruited for the study through local physicians and local announcements, completed questionnaires relating to identified occupational, personal and psychosocial risk factors, and completed an Oswestry Disability Index (ODI). Multiple regression models for predicting LBP severity were developed for each risk factor category and for a combined risk factor model (which included factors from all three risk factor categories) that included two-way interactions. Results showed that the final model consisted of both main effects and interaction terms between risk factor categories and had an adjusted R² value of 0.85, a significant improvement over models developed for the individual categories. These findings illustrate the need to consider all three broad categories of risk factors simultaneously in predicting injury status and in developing effective potential intervention efforts.     

The development of risk assessment models for carpal tunnel syndrome: a case-referent study

The present study developed risk assessment models for carpal tunnel syndrome (CTS) which can provide information of the likelihood of developing CTS for an individual having certain personal characteristics and occupational risks. A case-referent study was conducted consisting of two case groups and one referent group: (1) 22 work-related CTS patients (W-CTS), (2) 25 non-work related CTS patients (NW-CTS), and (3) 50 healthy workers (HEALTHY) having had no CTS history. The classification of CTS patients into one of the case groups was determined according to the type of insurance covering their medical costs. Personal characteristics, psychosocial stresses at work, and physical work conditions were surveyed by using a questionnaire tailor-designed to CTS (reliability of each scale ? 0.7). By contrasting the risk information of each case group to that of the referent group, three logistic regression models were developed: W-CTS/HEALTHY, NW-CTS/HEALTHY, and C-CTS/HEALTHY (C-CTS, the combined group of W-CTS and NW-CTS). ROC analysis indicated that the models have satisfactory discriminability (d′ = ;1.91 to 2.51) and high classification accuracy (overall accuracy = 83 – 89%). Both W-CTS/HEALTHY and C-CTS/HEALTHY include personal and physical factors, while NW-CTS/HEALTHY involves only personal factors. This suggests that the injury causation of NW-CTS patients should be attributable mainly to their ‘high’ personal susceptibility to the disorder rather than exposure to adverse work conditions, while that of W-CTS patients be attributable to improper work conditions and CTS-prone personal characteristics in combination.     

The development of risk assessment models for carpal tunnel syndrome: a case-referent study

The present study developed risk assessment models for carpal tunnel syndrome (CTS) which can provide information of the likelihood of developing CTS for an individual having certain personal characteristics and occupational risks. A case-referent study was conducted consisting of two case groups and one referent group: (1) 22 work-related CTS patients (W-CTS), (2) 25 non-work related CTS patients (NW-CTS), and (3) 50 healthy workers (HEALTHY) having had no CTS history. The classification of CTS patients into one of the case groups was determined according to the type of insurance covering their medical costs. Personal characteristics, psychosocial stresses at work, and physical work conditions were surveyed by using a questionnaire tailor-designed to CTS (reliability of each scale > or = 0.7). By contrasting the risk information of each case group to that of the referent group, three logistic regression models were developed: W-CTS/HEALTHY, NW-CTS/HEALTHY, and C-CTS/HEALTHY (C-CTS, the combined group of W-CTS and NW-CTS). ROC analysis indicated that the models have satisfactory discriminability (d' = 1.91 to 2.51) and high classification accuracy (overall accuracy = 83-89%). Both W-CTS/HEALTHY and C-CTS/HEALTHY include personal and physical factors, while NW-CTS/HEALTHY involves only personal factors. This suggests that the injury causation of NW-CTS patients should be attributable mainly to their 'high' personal susceptibility to the disorder rather than exposure to adverse work conditions, while that of W-CTS patients be attributable to improper work conditions and CTS-prone personal characteristics in combination.     

A preliminary assessment of physical work exposures among electronic waste workers at Agbogbloshie,Accra Ghana

Occupational exposure associated with unstructured, informal e-waste recycling has received very limited attention. This study aimed to quantify the occupational physical exposures among informal e-waste workers at the largest e-waste site in Africa.A cross-sectional field survey of 163 male e-waste workers was conducted using a self-report occupational physical activity questionnaire, along with direct work observations, and pedometer estimates of walking activity for a subset of workers (n = 42).Results indicated significant differences in self-reported 7-day work exposures among the three main e-waste job categories, namely, collectors (n = 70), dismantlers (n = 73) and burners (n = 20). Prolonged walking, sitting and standing on five or more days in the workweek was frequently reported by collectors (87%), dismantlers (82%) and burners (60%), respectively. Nearly 90% of collectors and burners and 60% of dismantlers reported lifting and carrying on five or more days in the workweek.The exposure combinations identified suggest a risk for musculoskeletal disorders (MSDs). Findings call attention to the need for research examining potential associations between physical exposures and MSDs affecting e-waste workers in Agbogbloshie. The high exposure variability both between and within workers has implications for future exposure assessments conducted in unregulated, informal work settings.     

Personal predictors of the longest episode of occupational sitting and their interaction with workplace support for health among workers in Accra: A cross-sectional analysis with sensitivity analyses

Many studies have identified personal factors associated with occupational sitting time, but none of them focused on the longest episode of occupational sitting (hereby referred to as continuous occupational sitting time) nor considered whether workplace support for health moderates the associations between these factors and continuous occupational sitting time. This study aimed to identify personal factors predicting continuous occupational sitting time and ascertained whether workplace support for health moderates the associations between these factors and continuous occupational sitting time. A cross-sectional design and an adapted hierarchical linear regression analysis was employed. The participants were 991 employees of public and private organizations in Accra, Ghana. Results were presented with hierarchical linear regression analysis. The ultimate predictors of continuous occupational sitting time at a minimum of p < 0.05 include age, job type, and job income. Workplace support for health significantly moderated the primary associations, which means that workplace support for health altered the strength of the associations between all predictors (except tenure) and continuous occupational sitting time. This study concludes that there are inequalities in continuous occupational sitting time between employee groups that can be modified by workplace support for health.     

The Strain Index (SI) and Threshold Limit Value (TLV) for Hand Activity Level (HAL): risk of carpal tunnel syndrome (CTS) in a prospective cohort

A cohort of 536 workers was enrolled from 10 diverse manufacturing facilities and was followed monthly for six years. Job physical exposures were individually measured. Worker demographics, medical history, psychosocial factors, current musculoskeletal disorders (MSDs) and nerve conduction studies (NCS) were obtained. Point and lifetime prevalence of carpal tunnel syndrome (CTS) at baseline (symptoms + abnormal NCS) were 10.3% and 19.8%. During follow-up, there were 35 new CTS cases (left, right or both hands). Factors predicting development of CTS included: job physical exposure (American conference of governmental industrial hygienists Threshold Limit Value (ACGIH TLV) for Hand Activity Level (HAL) and the Strain Index (SI)), age, BMI, other MSDs, inflammatory arthritis, gardening outside of work and feelings of depression. In the adjusted models, the TLV for HAL and the SI were both significant per unit increase in exposure with hazard ratios (HR) increasing up to a maximum of 5.4 (p = 0.05) and 5.3 (p = 0.03), respectively; however, similar to other reports, both suggested lower risk at higher exposures. Data suggest that the TLV for HAL and the SI are useful metrics for estimating exposure to biomechanical stressors. PRACTITIONER SUMMARY: This study was conducted to determine how well the TLV for HAL and the SI predict risk of CTS using a prospective cohort design with survival analysis. Both the TLV for HAL and the SI were found to predict risk of CTS when adjusted for relevant covariates.     

A fuzzy linguistic model for the prediction of carpal tunnel syndrome risks in an occupational environment

This research presents the development and evaluation of a fuzzy linguistic model designated to predict the risk of carpal tunnel syndrome (CTS) in an occupational setting. CTS has become one of the largest problems facing ergonomists and the medical community because it is developing in epidemic proportions within the occupational environment. In addition, practitioners are interested in identifying accurate methods for evaluating the risk of CTS in an occupational setting. It is hypothesized that many factors impact an individual's likelihood of developing CTS and the eventual development of CTS. This disparity in the occurrence of CTS for workers with similar backgrounds and work activities has confused researchers and has been a stumbling block in the development of a model for widespread use in evaluating the development of CTS. Thus this research is an attempt to develop a method that can be used to predict the likelihood of CTS risk in a variety of environments. The intent is that this model will be applied eventually in an occupational setting, thus model development was focused on a method that provided a usable interface and the desired system inputs can also be obtained without the benefit of a medical practitioner. The methodology involves knowledge acquisition to identify and categorize a holistic set of risk factors that include task-related, personal, and organizational categories. The determination of relative factor importance was accomplished using analytic hierarchy processing (AHP) analysis. Finally a mathematical representation of the CTS risk was accomplished by utilizing fuzzy set theory in order to quantify linguistic input parameters. An evaluation of the model including determination of sensitivity and specificity is conducted and the results of the model indicate that the results are fairly accurate and this method has the potential for widespread use. A significant aspect of this research is the comparison of this technique to other methods for assessing presence of CTS. The results of this evaluation technique are compared with more traditional methods for assessing the presence of CTS.     

Risk assessment of cheese processing tasks using the Strain Index and OCRA Checklist

The purpose of this study was to conduct and compare two ergonomic risk assessment methods often used in occupational health research and practice: the Strain Index (SI) and Occupational Repetitive Actions (OCRA) Checklist. Seven raters used the SI and OCRA Checklist to assess task-level physical exposures to the upper extremity of workers performing 21 cheese-manufacturing tasks. Of the total task exposures assessed with both methods, nearly half (49.1%) were classified as hazardous using the OCRA Checklist while 60.2% were classified as hazardous using the SI. Although the underlying injury risk characterization constructs of the SI and OCRA Checklist differ, the results indicated that the SI and OCRA Checklist often classified job tasks into similar risk categories. The differences in risk classifications determined by the SI and OCRA Checklist for job tasks were likely related to the definition of variables measured by these assessment methods as well as the complexity of tasks evaluated. By design, the SI is specific to the distal upper extremity while the OCRA Checklist accounts for the entire upper extremity including the shoulder. When conducting risk assessments of industrial work tasks, the choice of analysis tools should be based on the purpose of the assessment and the complexity of task functions. Both the SI and OCRA Checklist yield risk assessment ratings that are similar for cheese processing tasks.     

Self-reported musculoskeletal problems amongst professional truck drivers

Occupational driving has often been associated with a high prevalence of back pain. The factors that contribute to cause the pain are diverse and might include prolonged sitting, poor postures, exposure to whole-body vibration and other non-driving factors such as heavy lifting, poor diet or other psychosocial factors. In Europe, truck drivers are likely to be considered an 'at risk' group according to the Physical Agents (Vibration) Directive and therefore risks will need to be reduced. This questionnaire-based study set out to examine the relationship between musculoskeletal problems and possible risk factors for HGV truck drivers to help prioritize action aimed at risk reduction. Truck drivers (n = 192) completed an occupational questionnaire with two measures of vibration exposure (weekly hours and distance driven). Items on manual handling, relevant ergonomics factors and musculoskeletal problems were also included. Reported exposures to vibration ranged from 12 to 85 h per week, with a mean of 43.8 h. Distances driven ranged from 256 to 6400 km (mean 2469 km). Most of the respondents (81%) reported some musculoskeletal pain during the previous 12 months and 60% reported low back pain. Contrary to expectations, vibration exposures were significantly lower among those who suffered musculoskeletal symptoms when distance was used as an exposure measure. Manual handling and subjective ratings of seat discomfort were associated with reported musculoskeletal problems.     

Self-reported musculoskeletal problems amongst professional truck drivers

Occupational driving has often been associated with a high prevalence of back pain. The factors that contribute to cause the pain are diverse and might include prolonged sitting, poor postures, exposure to whole-body vibration and other non-driving factors such as heavy lifting, poor diet or other psychosocial factors. In Europe, truck drivers are likely to be considered an ‘at risk’ group according to the Physical Agents (Vibration) Directive and therefore risks will need to be reduced. This questionnaire-based study set out to examine the relationship between musculoskeletal problems and possible risk factors for HGV truck drivers to help prioritize action aimed at risk reduction. Truck drivers (n = 192) completed an occupational questionnaire with two measures of vibration exposure (weekly hours and distance driven). Items on manual handling, relevant ergonomics factors and musculoskeletal problems were also included. Reported exposures to vibration ranged from 12 to 85 h per week, with a mean of 43.8 h. Distances driven ranged from 256 to 6400 km (mean 2469 km). Most of the respondents (81%) reported some musculoskeletal pain during the previous 12 months and 60% reported low back pain. Contrary to expectations, vibration exposures were significantly lower among those who suffered musculoskeletal symptoms when distance was used as an exposure measure. Manual handling and subjective ratings of seat discomfort were associated with reported musculoskeletal problems.     

An investigation on major physical hazard exposures and health effects of forestry vehicle operators performing wood logging processes

Forest vehicle operators are occupationally exposed to combined hazards such as noise, whole-body vibration(WBV), adverse microclimate, and carbon monoxide. Such combined exposures may not only increase the risk of accidents but they may also have some synergized effects on the developments of major occupational diseases of the workers, which have been among the major concerns of the occupational safety and health for the forestry sector in Romania. This study investigated the combined exposures through measuring and analyzing the equivalent acoustic level LAeq (dB(A)), whole-body vibration (A(8)-value), working microclimate, and carbon monoxide inside the worker's cabin in the breathable area. The vehicles considered in this study included skidding vehicles dedicated to wood exploitation (type I) and agricultural tractors modified for logging (type II). The cumulative distribution function of each types of exposure was calculated in the analyses. This study found that the noise and WBV exposures had large probabilities of exceeding the permissible limits: for noise, 75% for vehicle type I, and 55% for vehicle type II; for the WBV, 63% for type I vehicles, and 72% for type II vehicles. The measured data suggest that the microclimate and carbon monoxide exposures were within their limits in the process of collecting wood. This study also found that 27% of workers participated in the study were detected with occupational diseases. Based on these findings, some intervention methods were recommended to control the exposures and health effects.     

Influence of adherence to autonomous job rotation on musculoskeletal symptoms,occupational exposure,and work ability

Job rotation is widely used in the manufacturing industry. The aim of this study was to investigate the influence of adherence to autonomous job rotation on the prevalence of musculoskeletal symptoms, occupational exposure, and work ability. A total of 120 blue-collar workers from an automotive manufacturing company with a job rotation program as an organizational strategy were included in this study. Job rotation performance, musculoskeletal symptoms, perceived occupational and biomechanical exposure, and work ability were evaluated. For the statistical analyses, the departments were divided into high (83.7%–100%) and low (0–36.4%) job rotation adherence. Two departments showed high adherence to job rotation (n = 78 workers). Workers who had high job rotation adherence had a higher prevalence of musculoskeletal symptoms (32.1%) and higher perceived occupational exposure for the occurrence of musculoskeletal symptoms (71.4 ± 45.7 points) (P > 0.05). Work ability was considered good or excellent for both high- and low-adherence groups (P > 0.05). High adherence to job rotation had no positive influences on the musculoskeletal symptoms, occupational exposure, and work ability of workers.     

Prevalence of carpal tunnel syndrome among employees at a poultry processing plant

Objective

To determine prevalence of carpal tunnel syndrome (CTS) among poultry processing employees while taking into account non-occupational factors and assess any association between CTS prevalence and exposure groups.

Methods

Performed a cross-sectional survey to assess CTS (n = 318). A CTS case was defined as an employee with self-reported CTS symptoms, an abnormal hand symptom diagram, and an abnormal nerve conduction study (NCS). Log-binomial regression was used to estimate prevalence ratios.

Results

Three hundred and one participants had sufficient symptom information or NCS data to be classified. 126 (42%) of 301 participants had evidence of CTS. In the adjusted analysis, the highest exposure group had CTS prevalence that was significantly higher than that for the lower exposure group [PR: 1.61; 95% CI = (1.20, 2.17)].

Conclusions

Increasing levels of hand activity and force were associated with increased CTS prevalence among participants. Recommendations were provided to reduce exposure to these risk factors.     

Hybrid procedure to determine optimal workforce without noise hazard exposure

Hearing loss is a major occupational health problem among industrial workers. Repetitive exposure to loud noise increases the risk of hearing loss. An administrative noise control such as job rotation can help to reduce workers’ daily noise exposures. In a case where noise levels are excessively high, it is often necessary to assign additional workers to the current workforce to alleviate daily noise exposures that individual workers receive. This paper presents four solution algorithms (three approximations and one exact) to determine a minimum number of workers and their work assignments to attend noisy workstations without noise hazard exposure (that is, daily noise exposure does not exceed 90 dBA). Then, a hybrid procedure which utilizes the four algorithms successively is proposed to improve the solution procedure. Based on a computational experiment on 300 test problems, it is found that the hybrid procedure outperforms all four algorithms (when utilized separately) and is able to find an optimal solution for 88% of the test problems.     

Hybrid procedure to determine optimal workforce without noise hazard exposure

Hearing loss is a major occupational health problem among industrial workers. Repetitive exposure to loud noise increases the risk of hearing loss. An administrative noise control such as job rotation can help to reduce workers’ daily noise exposures. In a case where noise levels are excessively high, it is often necessary to assign additional workers to the current workforce to alleviate daily noise exposures that individual workers receive. This paper presents four solution algorithms (three approximations and one exact) to determine a minimum number of workers and their work assignments to attend noisy workstations without noise hazard exposure (that is, daily noise exposure does not exceed 90 dBA). Then, a hybrid procedure which utilizes the four algorithms successively is proposed to improve the solution procedure. Based on a computational experiment on 300 test problems, it is found that the hybrid procedure outperforms all four algorithms (when utilized separately) and is able to find an optimal solution for 88% of the test problems.     

Examining endplate fatigue failure during cyclic compression loading with variable and consistent peak magnitudes using a force weighting adjustment approach: an in vitro study

Abstract

Repetitive movement is common in many occupational contexts. Therefore, cumulative load is a widely recognised risk factor for lowback injury. This study quantified the effect of force weighting factors on cumulative load estimates and injury prediction during cyclic loading. Forty-eight porcine cervical spine motion segments were assigned to experimental groups that differed by average peak compression magnitude (30%, 50% and 70% of predicted tolerance) and amplitude variation (consistent, variable). Cyclic loading was performed at a frequency of 0.5?Hz until fatigue failure occurred. Weighting factors were determined and applied instantaneously. Inclusion of weighting factors resulted in statistically similar cumulative load estimates at injury between variable and consistent loading (p?>?.071). Further, survivorship was generally greater when the peak compression magnitude was consistent compared to variable. These results emphasise the importance of weighting factors as an equalisation tool for the evaluation of cumulative low back loading exposures in occupational contexts.

Practitioner summary: Weighting factors can equalise the risk of injury based on compression magnitude. When weighted, the cumulative compression was similar between consistent and variable cyclic loading protocols, despite being significantly different when unweighted and having similar injury rates. Therefore, assessing representative occupational exposures without evaluating task performance variability may underestimate injury risk.

Abbreviations: FSU: functional spinal unit; UCT: ultimate compression tolerance     

Pathomechanisms of work-related musculoskeletal disorders: conceptual issues

Work-related musculoskeletal disorders (WRMSDs) by definition are a subset of musculoskeletal disorders (MSDs) that arise out of occupational exposures. While traditional exposure assessment techniques have proved to be successful in identifying ergonomic exposures that are epidemiologically linked to these disorders, some are troubled by the lack of one-to-one correspondence between specific occupational exposure profiles and specific MSDs. In the absence of more sophisticated hypotheses that might explain the occurrence of WRMSDs in a variety of exposure patterns, the aetiologic relationships may (again) be called into question. Another unanswered question is whether specific types of WRMSDs have qualitatively different exposure-response relationships. A clearer understanding of the underlying pathomechanisms associated with specific WRMSDs could help future researchers better determine how and when various occupational exposure profiles become pathogenic. Such knowledge could also be used to design exposure assessment tools to capture exposure information more relevant to the risk of WRMSDs. The main goals of this paper are to summarize several recently described pathomechanisms, most of which have been discussed primarily in clinical and experimental literature that might not be widely read by occupational health scientists. Suggestions are made as to how future research could evaluate whether these phenomena are relevant to the effects of physical exposures and the underlying disease processes of common WRMSDs.     

Pathomechanisms of work-related musculoskeletal disorders: conceptual issues

Work-related musculoskeletal disorders (WRMSDs) by definition are a subset of musculoskeletal disorders (MSDs) that arise out of occupational exposures. While traditional exposure assessment techniques have proved to be successful in identifying ergonomic exposures that are epidemiologically linked to these disorders, some are troubled by the lack of one-to-one correspondence between specific occupational exposure profiles and specific MSDs. In the absence of more sophisticated hypotheses that might explain the occurrence of WRMSDs in a variety of exposure patterns, the aetiologic relationships may (again) be called into question. Another unanswered question is whether specific types of WRMSDs have qualitatively different exposure-response relationships. A clearer understanding of the underlying pathomechanisms associated with specific WRMSDs could help future researchers better determine how and when various occupational exposure profiles become pathogenic. Such knowledge could also be used to design exposure assessment tools to capture exposure information more relevant to the risk of WRMSDs. The main goals of this paper are to summarize several recently described pathomechanisms, most of which have been discussed primarily in clinical and experimental literature that might not be widely read by occupational health scientists. Suggestions are made as to how future research could evaluate whether these phenomena are relevant to the effects of physical exposures and the underlying disease processes of common WRMSDs.