Sex differences in task distribution and task exposures among Danish house painters: an observational study combining questionnaire data with biomechanical measurements

Reliability and Accuracy of Standard Reference Procedures for Measurements of Trunk and Arm Postures in Ergonomics

Adequate reference procedures for obtaining the reference zero-angle position are important for precise and accurate posture measurements, but few studies have systematically investigated these. A limited number of previous studies suggest differences in accuracy between procedures, with some causing an underestimation of the true arm elevation angle when sensors are taped to the skin. The reliability of commonly used reference procedures for the measurement of the trunk posture is also not well explored, and alternative procedures may improve precision. Based on this identified gap, this study evaluated the test-retest reliability of the N-position (I-pose), i.e., the standard procedure for recording trunk postures, and compared it with two new alternative procedures. Additionally, the accuracy of the N-position for measuring arm elevation angles was compared with one alternative procedure. A total of 40 participants (22 women and 18 men) aged 26-70 years performed the reference procedures in a laboratory setting. Postures were recorded using a smart workwear system equipped with two inertial measurement units (IMUs) embedded in pockets within the workwear. For the trunk posture, the N-position showed a slight lack of test-retest reliability, while one of the alternative procedures demonstrated better test-retest reliability. For the arm posture, the N-position, which does not include lateral trunk inclination, resulted in a substantial underestimation of the arm elevation angle of approximately 15°, which is a novel finding. In contrast, the posture involving trunk inclination closely matched the targeted reference, with a difference of less than 2°. This study underscores the importance of selecting appropriate reference procedures to ensure precise and accurate posture measurements.

Carpal tunnel syndrome and occupational hand exposures: a Danish nationwide cohort study

OBJECTIVES

The aim was to examine exposure-response relations between occupational hand exposures and carpal tunnel syndrome (CTS) and to compare the relation between surgery-treated and non-surgery-treated CTS. The secondary aim was to study sex-specific differences in exposure-response relations.

METHODS

We conducted a nationwide register-based cohort study of all persons born in Denmark (1945-1994). During follow-up (2010-2013), we identified first-time events of CTS. Occupational hand exposure estimates the year before each follow-up year were obtained by linking individual occupational codes with a job exposure matrix. We used multivariable logistic regression equivalent to discrete survival analysis based on sex and surgery. The excess fraction of cases was calculated.

RESULTS

For both sexes, exposure-response relations were found for all occupational hand exposures. Among men, we found ORadj of 3.6 (95% CI 3.2 to 3.8) for hand-related force, 2.9 (95% CI 2.5 to 3.2) for repetitive hand movements, 3.8 (95% CI 2.7 to 5.2) for non-neutral hand posture and 2.5 (95% CI 2.2 to 2.7) for hand-arm vibration in the highest exposure groups. For combined exposure (hand load), ORadj was 3.5 (95% CI 3.1 to 4.0). Slightly higher ORsadj were generally found for surgery-treated CTS compared with non-surgery-treated CTS for both sexes. When comparing sex, somewhat higher ORsadj were found among men. The excess fraction was 42%.

CONCLUSIONS

Occupational hand exposures carried a 3-5-fold increased risk of CTS with slightly higher risks for surgery-treated compared with non-surgery-treated CTS. Even though CTS occurs more frequently among women, somewhat higher exposure-response relations were found for men compared with women. In the general working population, a substantial fraction of first-time CTS could be related to occupational hand exposures.

An evaluation of wrist and forearm movement during purposeful activities and range of movement exercises after surgical repair of a distal radius fracture: A randomized crossover study

PURPOSE

Following surgical repair of distal radius fractures, range of movement (ROM) exercises are the primary approach for restoring movement during early rehabilitation. Specified purposeful activities can also be used, but the movement produced by activities is not well-understood. The study aimed to evaluate and compare movement during purposeful activity and ROM exercises METHODS: Thirty-five adults with a surgically repaired distal radius facture undertook two 10-minutes interventions: purposeful activity (PA) and active ROM exercises (AE), separated by a 60 minute washout, in random order. Data collection occurred during a single session on the same day. Electrogoniometry was used to measure time-accumulated position (TAP), a global metric of movement range and amount, maximum active end range, movement repetitions, excursions >75% of available ROM, and active time. Data were analyzed using linear mixed and generalized linear mixed regression models.

RESULTS

Purposeful activities selected were predominantly household or food preparation. TAP was significantly higher during AE than PA: -1878 [-2388, -1367], p ≤.001, for wrist extension/flexion. PA produced significantly greater movement repetitions for wrist extension/flexion and deviation, excursions beyond 75% of available ROM, and active time, than AE. During PA the wrist was extending/flexing a mean of 97% [92, 101], of the time, compared with 43% [40, 47], during AE. There were no significant differences in maximum end range for wrist extension between PA, 33.7° [29.8, 37.5] and AE, 34.5° [30.7, 38.4], or for ulnar deviation.

CONCLUSIONS

ROM exercises produced higher volumes of sustained joint position than purposeful activity but activities, selected for importance and challenge, produced significantly higher volumes of continuous, repetitious motion in equivalent ranges of movement as exercise repetitions. The study challenges therapists to consider the rehabilitative potential of movement produced by activity for restoring movement and function in the early postoperative weeks.

Wearable Motion Capture Devices for the Prevention of Work-Related Musculoskeletal Disorders in Ergonomics-An Overview of Current Applications, Challenges, and Future Opportunities

Work-related musculoskeletal disorders (WMSDs) are a major contributor to disability worldwide and substantial societal costs. The use of wearable motion capture instruments has a role in preventing WMSDs by contributing to improvements in exposure and risk assessment and potentially improved effectiveness in work technique training. Given the versatile potential for wearables, this article aims to provide an overview of their application related to the prevention of WMSDs of the trunk and upper limbs and discusses challenges for the technology to support prevention measures and future opportunities, including future research needs. The relevant literature was identified from a screening of recent systematic literature reviews and overviews, and more recent studies were identified by a literature search using the Web of Science platform. Wearable technology enables continuous measurements of multiple body segments of superior accuracy and precision compared to observational tools. The technology also enables real-time visualization of exposures, automatic analyses, and real-time feedback to the user. While miniaturization and improved usability and wearability can expand the use also to more occupational settings and increase use among occupational safety and health practitioners, several fundamental challenges remain to be resolved. The future opportunities of increased usage of wearable motion capture devices for the prevention of work-related musculoskeletal disorders may require more international collaborations for creating common standards for measurements, analyses, and exposure metrics, which can be related to epidemiologically based risk categories for work-related musculoskeletal disorders.

Mind the gap - development of conversion models between accelerometer- and IMU-based measurements of arm and trunk postures and movements in warehouse work

Sensor type (accelerometers only versus inertial measurement units, IMUs) and angular velocity computational method (inclination versus generalized velocity) have been shown to affect the measurements of arm and trunk movements. This study developed models for conversions between accelerometer and IMU measurements of arm and trunk inclination and between accelerometer and IMU measurements of inclination and generalized (arm) velocities. Full-workday recordings from accelerometers and IMUs of arm and trunk postures and movements from 38 warehouse workers were used to develop 4 angular (posture) and 24 angular velocity (movement) conversion models for the distributions of the data. A power function with one coefficient and one exponent was used, and it correlated well (r2 > 0.999) in all cases to the average curves comparing one measurement with another. These conversion models facilitate the comparison and merging of measurements of arm and trunk movements collected using the two sensor types and the two computational methods.

Prospective, population-based study of occupational movements and postures of the neck as risk factors for cervical disc herniation

OBJECTIVE

We studied the associations between objectively measured occupational neck exposures in a job exposure matrix (JEM) and cervical disc herniation (CDH).

DESIGN

A cohort study of Danish workers who ever held at least one of 29 jobs (eg, dentists, hairdressers, childcare, carpenters) from 1981 to 2016 was formed. Representative whole work-day inclinometric measurements from previous studies using triaxial accelerometers measuring neck angular velocity and posture of the neck were used as exposure in a JEM. Job titles were retrieved from the Danish Occupational Cohort with eXposure data database. The risk of CDH by quintiles of cumulated exposure was assessed by incidence rate ratios (IRR), adjusted for age, sex, calendar-year, previous lumbar disc herniation and educational level, using Poisson regression models.

SETTING

Nationwide Danish registers.

PARTICIPANTS

852 625 Danish workers within 29 different job-titles.

OUTCOME MEASURES

First diagnosis of CDH was retrieved from the Danish National Patient Register.

RESULTS

We found 14 000 cases of CDH during 20.2 million person-years of follow-up. Increasing levels of neck angular velocity showed a decreasing risk with IRR 0.90 (95% CI 0.86 to 0.95) when the highest level of cumulative exposure (dynamic work) was compared with the lowest (static work). Similar results were found for extension and flexion of the neck, though not statistically significant for extension. Multiple sensitivity analyses did not change the results.

CONCLUSION

In this large register-based study based on a JEM, we found no evidence of an increased risk of CDH with increasing cumulated angular velocity, flexion or extension of the neck. Factors other than occupational dynamic neck movements and bent neck position seem to be important in the development of CDH.

Repetitive and forceful movements of the hand as predictors of treatment for pain in the distal upper extremities

Objective

To investigate repetitive movements and the use of hand force as causes of treatment for distal upper extremities musculoskeletal disorders

Methods

A cohort of 202 747 workers in a pension health scheme from 2005 to 2017 in one of 17 jobs (eg, office work, carpentry, cleaning) was formed. Representative electro-goniometric measurements of wrist angular velocity as a measure for repetition and expert-rated use of hand force were used in a job exposure matrix (JEM). Job titles were retrieved from the Danish registers. Outcome was first treatment in the distal upper extremities. In a Poisson regression model, incidence rate ratios (IRRs) of treatment were adjusted for age, calendar-year, diagnosis of rheumatoid arthritis and arm fractures. In further analyses, wrist velocity or hand force was added.

Results

In men, wrist velocity had an IRR of 1.48 (95% CI 1.15 to 1.91) when the highest exposure level was compared with the lowest but with no clear exposure-response pattern. The effect became insignificant when adjusted for hand force. Hand force had an IRR of 2.65 (95% CI 2.13 to 3.29) for the highest versus the lowest exposure with an exposure-response pattern, which remained after adjustment for wrist velocity. Among women, no increased risk was found for hand force, while wrist velocity showed a significantly protective association with treatment.

Conclusions

In men, occupational exposure to hand force more than doubled the risk of seeking treatment. The results for exposure to repetition were less clear. In women, we could not find any indications of an increased risk neither for force nor for repetition.

Effects of Sensor Types and Angular Velocity Computational Methods in Field Measurements of Occupational Upper Arm and Trunk Postures and Movements

Accelerometer-based inclinometers have dominated kinematic measurements in previous field studies, while the use of inertial measurement units that additionally include gyroscopes is rapidly increasing. Recent laboratory studies suggest that these two sensor types and the two commonly used angular velocity computational methods may produce substantially different results. The aim of this study was, therefore, to evaluate the effects of sensor types and angular velocity computational methods on the measures of work postures and movements in a real occupational setting. Half-workday recordings of arm and trunk postures, and movements from 38 warehouse workers were compared using two sensor types: accelerometers versus accelerometers with gyroscopes-and using two angular velocity computational methods, i.e., inclination velocity versus generalized velocity. The results showed an overall small difference (<2° and value independent) for posture percentiles between the two sensor types, but substantial differences in movement percentiles both between the sensor types and between the angular computational methods. For example, the group mean of the 50th percentiles were for accelerometers: 71°/s (generalized velocity) and 33°/s (inclination velocity)-and for accelerometers with gyroscopes: 31°/s (generalized velocity) and 16°/s (inclination velocity). The significant effects of sensor types and angular computational methods on angular velocity measures in field work are important in inter-study comparisons and in comparisons to recommended threshold limit values.

Occupation and risk of knee osteoarthritis and knee replacement: A longitudinal, multiple-cohort study

OBJECTIVES

To examine the effect of occupation on knee osteoarthritis (OA) and total knee replacement (TKR) in working-aged adults.

METHODS

We used longitudinal data from the Chingford, Osteoarthritis Initiative (OAI) and Multicentre Osteoarthritis (MOST) studies. Participants with musculoskeletal disorders and/or a history of knee-related surgery were excluded. Participants were followed for up to 19-years (Chingford), 96-months (OAI) and 60-months (MOST) for incident outcomes including radiographic knee OA (RKOA), symptomatic RKOA and TKR. In those with baseline RKOA, progression was defined as the time from RKOA incidence to primary TKR. Occupational job categories and work-place physical activities were assigned to levels of workload. Logistic regression was used to examine the relationship between workload and incident outcomes with survival analyses used to assess progression (reference group: sedentary occupations).

RESULTS

Heavy manual occupations were associated with a 2-fold increased risk (OR: 2.07, 95% CI 1.03 to 4.15) of incident RKOA in the OAI only. Men working in heavy manual occupations in MOST (2.7, 95% CI 1.17 to 6.26) and light manual occupations in OAI (2.00, 95% CI 1.09 to 3.68) had a 2-fold increased risk of incident RKOA. No association was observed among women. Increasing workload was associated with an increased risk of symptomatic RKOA in the OAI and MOST. Light work may be associated with a decreased risk of incident TKR and disease progression.

CONCLUSION

Heavy manual work carries an increased risk of incident knee OA; particularly among men. Workload may influence the occurrence of TKR and disease progression.

Musculoskeletal pain among Finnish orchestra musicians versus core workforce

Background

Professional musicians show a high prevalence of musculoskeletal pain, but information is limited about prevalence of pain compared to the general populations.

Aims

Our cross-sectional epidemiological study compared the prevalence of musculoskeletal pain between professional orchestra musicians and the working population in Finland.

Methods

Musicians with a permanent contract with all domestic professional symphony and philharmonic orchestras and a population sample of the workforce in Finland completed questionnaires including the same questions on musculoskeletal pain and on various other issues. Cross-sectional data from two population-based and two orchestra-musician studies were analysed by logistic regression model adjusting for confounding factors.

Results

In 2002, 345 musicians completed questionnaires (40% response rate), and in 2010, 195 (23%). The Health 2000 study sample comprised 5956 employed participants and in 2011, 5942. Musicians reported, in 2002 and in 2010, back pain during the past 30 days more often than did controls, 39% versus 27%, adjusted odds ratio (95% confidence interval, CI) 1.5 (1.2–1.9); shoulder pain, 21% versus 9%, 2.6 (1.9–2.5); elbow pain, 14% versus 5%, 2.9 (2.0–4.2); wrist pain 14% versus 7%, 2.2 (1.5–3.1); and finger pain 13% versus 9%, 2.8 (2.0–3.9). Prevalence of musculoskeletal pain increased with age in controls but not in musicians.

Conclusions

Professional orchestra musicians reported more pain in the back and upper extremity than other working people. Future research should focus on explaining differences in the occurrence of musculoskeletal disorders between musicians and the general population.

A Quantitative General Population Job Exposure Matrix for Occupational Noise Exposure

Occupational noise exposure is a known risk factor for hearing loss and also adverse cardiovascular effects have been suggested. A job exposure matrix (JEM) would enable studies of noise and health on a large scale. The objective of this study was to create a quantitative JEM for occupational noise exposure assessment of the general working population. Between 2001–2003 and 2009–2010, we recruited workers from companies within the 10 industries with the highest reporting of noise-induced hearing loss according to the Danish Working Environment Authority and in addition workers of financial services and children day care to optimize the range in exposure levels. We obtained 1343 personal occupational noise dosimeter measurements among 1140 workers representing 100 different jobs according to the Danish version of the International Standard Classification of Occupations 1988 (DISCO 88). Four experts used 35 of these jobs as benchmarks and rated noise levels for the remaining 337 jobs within DISCO 88. To estimate noise levels for all 372 jobs, we included expert ratings together with sex, age, occupational class, and calendar year as fixed effects, while job and worker were included as random effects in a linear mixed regression model. The fixed effects explained 40% of the total variance: 72% of the between-jobs variance, −6% of the between-workers variance and 4% of the within-worker variance. Modelled noise levels showed a monotonic increase with increasing expert score and a 20 dB difference between the highest and lowest exposed jobs. Based on the JEM estimates, metal wheel-grinders were among the highest and finance and sales professionals among the lowest exposed. This JEM of occupational noise exposure can be used to prioritize preventive efforts of occupational noise exposure and to provide quantitative estimates of contemporary exposure levels in epidemiological studies of health effects potentially associated with noise exposure.

Equal health at work? Protocol for an observational study of work organisation, workload and musculoskeletal complaints among women and men in grocery retail

INTRODUCTION

Women generally report more work-related musculoskeletal complaints than men and have higher rates of sickness absence, even within occupations. One likely reason is that work tasks within the occupation are gendered, that is, women and men have different tasks, even when sharing the same job title. Retail is an appealing sector for studying working conditions and work environment in a gender context. The prevalence of work-related complaints is high, physical loads may differ considerably between tasks and the distribution of tasks is likely gendered. The overall aim of this study in retail is to examine factors at the organisational and individual level that may, in a gender perspective, explain working conditions, work tasks, workloads and musculoskeletal health.

METHODS AND ANALYSES

Data will be collected in two grocery stores, each with 50-70 workers, at two occasions interspersed by about 1 year. In each of these four waves, data collection will include a web-based questionnaire to all workers addressing, for example, work tasks, psychosocial factors, fatigue and pain; semistructured interviews with managers and approximately 10 workers addressing, for example, competences and decision levels; and technical measurements of postures, movements and heart rate in about 30 workers. The study is novel in combining an organisational gender perspective addressed through qualitative methods with a quantitative analysis of tasks, workload and health. The design allows an examination of both how genders may differ, and why they may differ, as well as analyses of the extent to which gendered working conditions change over time in the two participating stores.

ETHICS AND DISSEMINATION

Approval of the study by the Swedish Ethical Review Authority (reference number 2017/404) has been obtained. This work will be disseminated by publication of peer-reviewed papers in scientific journals, presentations at scientific conferences and in meetings with representatives from Swedish retail, including unions and employers' organisations.

Exposure to Upper Arm Elevation During Work Compared to Leisure Among 12 Different Occupations Measured with Triaxial Accelerometers

Regarding prevention of neck and shoulder pain (NSP), unsupported arm elevation is one factor that should be taken into account when performing work risk assessment. Triaxial accelerometers can be used to measure arm elevation over several days but it is not possible to differentiate between supported and unsupported arm elevation from accelerometers only. Supported arm elevation is more likely to exist during sitting than standing. The aim of the study was to evaluate the use of whole workday measurements of arm elevation with accelerometers to assess potentially harmful work exposure of arm elevation, by comparing arm elevation at work with arm elevation during leisure, in a population with diverse work tasks, and to assess how the exposure parameters were modified when upper arm elevation during sitting time was excluded. The participants, 197 workers belonging to 12 occupational groups with diverse work tasks, wore triaxial accelerometers on the dominant arm, hip, and back for 1–4 days to measure arm elevation and periods of sitting. None of the groups were found to have higher exposure to arm elevation during work compared to leisure. Even though some occupations where known to have work tasks that forced them to work with elevated arms to a large extent. A high proportion of arm elevation derived from sitting time, especially so during leisure. When arm elevation during sitting time was excluded from the analysis, arm elevation was significantly higher at work than during leisure among construction workers, garbage collectors, manufacturing workers, and domestic cleaners. Together this illustrates that it is not suitable to use whole workday measurments of arm elevation with accelerometer as a sole information source when assessing the risk for NSP due to arm elevation. Information on body posture can provide relevant contextual information in exposure assessments when it is known that the potential harmful exposure is performed in standing or walking.

Movements of the wrist and the risk of carpal tunnel syndrome: a nationwide cohort study using objective exposure measurements

OBJECTIVES

We conducted a large cohort study to investigate the association between work-related wrist movements and carpal tunnel syndrome (CTS).

METHODS

Electro-goniometric measurements of wrist movements were performed for 30 jobs (eg, office work, child care, laundry work and slaughterhouse work). We measured wrist angular velocity, mean power frequency (MPF) and range of motion (ROM). We established a cohort of Danish citizens born 1940-1979 who held one of these jobs from age 18-80 years, using Danish national registers with annual employment information from 1992 to 2014. We updated the cohort by calendar year with job-specific and sex-specific means of measured exposures. Dates of a first diagnosis or operation because of CTS were retrieved from the Danish National Patient Register. The risk of CTS by quintiles of preceding exposure levels was assessed by adjusted incidence rate ratios (IRR^adj) using Poisson regression models.

RESULTS

We found a clear exposure-response association between wrist angular velocity and CTS with an IRR^adj of 2.31 (95% CI 2.09 to 2.56) when exposed to the highest level compared with the lowest. MPF also showed an exposure-response pattern, although less clear, with an IRR^adj of 1.83 (1.68 to 1.98) for the highest compared with the lowest exposure level. ROM showed no clear pattern. Exposure-response patterns were different for men and women.

CONCLUSIONS

High levels of wrist movement were associated with an increased risk of CTS. Preventive strategies should be aimed at jobs with high levels of wrist movements such as cleaning, laundry work and slaughterhouse work.

Self-recordings of upper arm elevation during cleaning - comparison between analyses using a simplified reference posture and a standard reference posture

BACKGROUND

To reduce ergonomic risk factors in terms of awkward and constrained postures and high velocities, it is important to perform adequate risk assessments. Technical methods provide objective measures of physical workload. These methods have so far mainly been used by researchers. However, if written instructions how to apply the sensors and how to adopt the reference posture are provided, together with triaxial accelerometers, it may be possible for employees to record their own physical workload. The exposure in terms of e.g. upper arm elevations could then easily be assessed for all workers in a workplace. The main aims of this study were: 1) to compare analyses for self-recording of upper arm elevation during work using a simplified reference posture versus using a standard reference posture, and 2) to compare the two reference postures.

METHODS

Twenty-eight cleaners attached an accelerometer to their dominant upper arm and adopted a simplified reference according to a written instruction. They were thereafter instructed by a researcher to adopt a standard reference. Upper arm elevations were recorded for 2 or 3 days. Each recording was analysed twice; relative to the simplified reference posture and relative to the standard reference posture. The group means of the differences in recorded upper arm elevations between simplified and standard reference analyses were assessed using Wilcoxon signed ranks test. Furthermore, we calculated the group mean of the differences between the simplified reference posture and the standard reference posture.

RESULTS

For arm elevation during work (50th percentile), the group mean of the differences between the two analyses was 0.2° (range -7 - 10°). The group mean of the differences between the two references was 9° (range 1 - 21°). The subjects were able to follow the instructions in the protocol and performed self-recording of upper arm elevation and velocity.

CONCLUSIONS

The small difference between the two analyses indicates that recordings performed by employees themselves are comparable, on a group level, with those performed by researchers. Self-recordings in combination with action levels would provide employers with a method for risk assessment as a solid basis for prevention of work-related musculoskeletal disorders.

Predicting Directly Measured Trunk and Upper Arm Postures in Paper Mill Work From Administrative Data, Workers' Ratings and Posture Observations

Objectives

A cost-efficient approach for assessing working postures could be to build statistical models for predicting results of direct measurements from cheaper data, and apply these models to samples in which only the latter data are available. The present study aimed to build and assess the performance of statistical models predicting inclinometer-assessed trunk and arm posture among paper mill workers. Separate models were built using administrative data, workers' ratings of their exposure, and observations of the work from video recordings as predictors.

Methods

Trunk and upper arm postures were measured using inclinometry on 28 paper mill workers during three work shifts each. Simultaneously, the workers were video filmed, and their postures were assessed by observation of the videos afterwards. Workers' ratings of exposure, and administrative data on staff and production during the shifts were also collected. Linear mixed models were fitted for predicting inclinometer-assessed exposure variables (median trunk and upper arm angle, proportion of time with neutral trunk and upper arm posture, and frequency of periods in neutral trunk and upper arm inclination) from administrative data, workers' ratings, and observations, respectively. Performance was evaluated in terms of Akaike information criterion, proportion of variance explained (R2), and standard error (SE) of the model estimate. For models performing well, validity was assessed by bootstrap resampling.

Results

Models based on administrative data performed poorly (R2 ≤ 15%) and would not be useful for assessing posture in this population. Models using workers' ratings of exposure performed slightly better (8% ≤ R2 ≤ 27% for trunk posture; 14% ≤ R2 ≤ 36% for arm posture). The best model was obtained when using observational data for predicting frequency of periods with neutral arm inclination. It explained 56% of the variance in the postural exposure, and its SE was 5.6. Bootstrap validation of this model showed similar expected performance in other samples (5th-95th percentile: R2 = 45-63%; SE = 5.1-6.2).

Conclusions

Observational data had a better ability to predict inclinometer-assessed upper arm exposures than workers' ratings or administrative data. However, observational measurements are typically more expensive to obtain. The results encourage analyses of the cost-efficiency of modeling based on administrative data, workers' ratings, and observation, compared to the performance and cost of measuring exposure directly.

Differences in the prevalence of musculoskeletal symptoms among female and male custodians

BACKGROUND

The prevalence of musculoskeletal symptoms among custodians is high. We sought to compare musculoskeletal symptoms between female and male custodians and to explore how task might affect this relationship.

METHODS

A cross-sectional study was performed among 712 custodians who completed a survey assessing upper extremity, back, and lower extremity musculoskeletal symptoms and exposure to cleaning tasks. Chi-square tests and logistic regression analyses were used to test for associations between gender, cleaning tasks, and musculoskeletal symptoms.

RESULTS

Gender was significantly (P < 0.05) associated with musculoskeletal symptoms in χ(2) tests and multivariate analyses. The prevalence ratio of symptoms among women was roughly 50% higher than men, regardless of the tasks that workers performed.

CONCLUSIONS

The prevalence of musculoskeletal symptoms differed for female and male custodians and appeared to be consistent across a range of job tasks. Am. J. Ind. Med. 59:841-852, 2016. © 2016 Wiley Periodicals, Inc.

Exposure-response relationships for work-related neck and shoulder musculoskeletal disorders--Analyses of pooled uniform data sets

There is a lack of quantitative data regarding exposure-response relationships between occupational risk factors and musculoskeletal disorders in the neck and shoulders. We explored such relationships in pooled data from a series of our cross-sectional studies. We recorded the prevalence of complaints/discomfort (Nordic Questionnaire) and diagnoses (physical examination) in 33 groups (24 female and 9 male) within which the workers had similar work tasks (3141 workers, of which 817 were males). In representative sub-groups, we recorded postures and velocities of the head (N = 299) and right upper arm (inclinometry; N = 306), right wrist postures and velocities (electrogoniometry; N = 499), and muscular activity (electromyography) in the right trapezius muscle (N = 431) and forearm extensors (N = 206). We also assessed the psychosocial work environment (Job Content Questionnaire). Uni- and multivariate linear meta-regression analysis revealed several statistically significant group-wise associations. Neck disorders were associated with head inclination, upper arm elevation, muscle activity of the trapezius and forearm extensors and wrist posture and angular velocity. Right-side shoulder disorders were associated with head and upper arm velocity, activity in the trapezius and forearm extensor muscles and wrist posture and angular velocity. The psychosocial work environment (low job control, job strain and isostrain) was also associated with disorders. Women exhibited a higher prevalence of neck and shoulder complaints and tension neck syndrome than men, when adjusting for postures, velocities, muscular activity or psychosocial exposure. In conclusion, the analyses established quantitative exposure-response relationships between neck and shoulder disorders and objective measures of the physical workload on the arm. Such information can be used for risk assessment in different occupations/work tasks, to establish quantitative exposure limits, and for the evaluation of preventive measures.

Exposure-response relationships between movements and postures of the wrist and carpal tunnel syndrome among male and female house painters: a retrospective cohort study

OBJECTIVES

To investigate exposure-response relationships between measured movements and postures of the wrist and the incidence of carpal tunnel syndrome (CTS), and any modifications by sex.

METHODS

In 2011, we established a historical cohort of 9364 members of the Painters' Union in Denmark. Self-reported task distributions were obtained by questionnaire (53% responded) and combined with sex-specific task exposure matrices to get individual estimates of exposure intensity, that is, velocity of wrist flexion/extension, mean power frequency (MPF) and non-neutral wrist postures. Exposure duration was assessed from yearly working proportions. Registered first-time hospital discharge CTS diagnoses and CTS surgery were collected as outcomes. The cohort was followed from 1994 to 2010. Log-linear Poisson regression was used.

RESULTS

For CTS diagnoses, the adjusted incidence rate ratios (IRRs) increased with increasing wrist velocity (IRR=1.37 (95% CI 1.10 to 1.71) per °/s) and MPF (IRR=1.53 (95% CI 1.21 to 1.91) per 0.01 Hz). For CTS surgery, the results were similar. The outcomes were not related to non-neutral postures or exposure duration. The adjusted IRRs for women were higher than those for men. There were no multiplicative interaction effects between exposure intensity, exposure duration and sex. However, the absolute incidence rates (IRs) increased at a steeper rate for women than for men, indicating an additive interaction.

CONCLUSIONS

The incidence of CTS increased with increasing velocity of wrist flexion/extension and MPF of wrist movements. The relative increase in incidence rates was the same for women and men, but the absolute incidence rates increased at a steeper rate for women than for men.

A Comparison of Two Strategies for Building an Exposure Prediction Model

Cost-efficient assessments of job exposures in large populations may be obtained from models in which 'true' exposures assessed by expensive measurement methods are estimated from easily accessible and cheap predictors. Typically, the models are built on the basis of a validation study comprising 'true' exposure data as well as an extensive collection of candidate predictors from questionnaires or company data, which cannot all be included in the models due to restrictions in the degrees of freedom available for modeling. In these situations, predictors need to be selected using procedures that can identify the best possible subset of predictors among the candidates. The present study compares two strategies for selecting a set of predictor variables. One strategy relies on stepwise hypothesis testing of associations between predictors and exposure, while the other uses cluster analysis to reduce the number of predictors without relying on empirical information about the measured exposure. Both strategies were applied to the same dataset on biomechanical exposure and candidate predictors among computer users, and they were compared in terms of identified predictors of exposure as well as the resulting model fit using bootstrapped resamples of the original data. The identified predictors were, to a large part, different between the two strategies, and the initial model fit was better for the stepwise testing strategy than for the clustering approach. Internal validation of the models using bootstrap resampling with fixed predictors revealed an equally reduced model fit in resampled datasets for both strategies. However, when predictor selection was incorporated in the validation procedure for the stepwise testing strategy, the model fit was reduced to the extent that both strategies showed similar model fit. Thus, the two strategies would both be expected to perform poorly with respect to predicting biomechanical exposure in other samples of computer users.