A structural equation modeling approach to fatigue-related risk factors for occupational injury

Evaluating the impact of occupational noise exposure on workplace fatal and nonfatal injuries in the U.S. (2006-2020)

OBJECTIVES

This study assessed the relationship between occupational noise exposure and the incidence of workplace fatal injury (FI) and nonfatal injury (NFI) in the United States from 2006 to 2020. It also examined whether distinct occupational and industrial clusters based on noise exposure characteristics demonstrated varying risks for FI and NFI.

METHODS

An ecological study design was utilized, employing data from the U.S. Bureau of Labor Statistics for FI and NFI and demographic data, the U.S. Census Bureau for occupation/industry classification code lists, and the U.S./Canada Occupational Noise Job Exposure Matrix for noise measurements. We examined four noise metrics as predictors of FI and NFI rates: mean Time-Weighted Average (TWA), maximum TWA, standard deviation of TWA, and percentage of work shifts exceeding 85 or 90 dBA for 619 occupation-years and 591 industry-years. K-means clustering was used to identify clusters of noise exposure characteristics. Mixed-effects negative binomial regression examined the relationship between the noise characteristics and FI/NFI rates separately for occupation and industry.

RESULTS

Among occupations, we found significant associations between increased FI rates and higher mean TWA (IRR: 1.06, 95% CI: 1.01-1.12) and maximum TWA (IRR: 1.10, 95% CI: 1.07-1.14), as well as TWA exceedance (IRR: 1.04, 95% CI: 1.01-1.07). Increased rates of NFI were found to be significantly associated with maximum TWA (IRR: 1.06, 95% CI: 1.04-1.09) and TWA exceedance (IRR: 1.03, 95% CI: 1.01-1.05). In addition, occupations with both higher exposure variability (IRR with FI rate: 1.49, 95% CI: 1.23-1.80; IRR with NFI rate: 1.40, 95% CI: 1.14-1.73) and higher level of sustained exposure (IRR with FI rate: 1.27, 95% CI: 1.12-1.44; IRR with NFI rate: 1.21, 95% CI: 1.05-1.39) were associated with higher rates of FI and NFI compared to occupations with low noise exposure. Among industries, significant associations between increased NFI rates and higher mean TWA (IRR: 1.05, 95% CI: 1.02-1.08) and maximum TWA (IRR: 1.06, 95% CI: 1.04-1.08) were observed. Unlike the occupation-specific analysis, industries with higher exposure variability and higher sustained exposures did not display significantly higher FI/NFI rates compared to industries with low exposure.

CONCLUSIONS

The results suggest that occupational noise exposure may be an independent risk factor for workplace FIs/NFIs, particularly for workplaces with highly variable noise exposures. The study highlights the importance of comprehensive occupational noise assessments.

Structural equation modeling approach for the analysis of ergonomics risk factors and occupational injuries among building construction workers in Bahir Dar City-Ethiopia

Ergonomic risk factors are a prominent cause of fatality and severe injuries in building constructions. Hence, this study applies a Structural Equation Modeling (SEM) approach to analyze ergonomics risk factors and occupational injuries among building construction workers in Bahir Dar City, Ethiopia. The results indicate significant relationships between ergonomics risk factors and the prevalence of occupational injuries. This study's findings contribute to the understanding of occupational health and safety in the construction industry, highlighting the need for targeted interventions. A cross-sectional study has been carried out, where data was collected through direct observations and standardized pretested questionnaires. The study recruited 220 participants in the construction industry. The data was analyzed using AMOS to study the direct and indirect effects of the identified variable. SEM has shown that the magnitude of the prevalence of occupational injury was 65.2 %. The results also revealed that the mostly affected body parts were lower arm, lower leg, hand, toe, and knee. Carpenter & roofers, plasterer and daily labors & other helpers were highly injury subjected occupations in respective order. The six leading significant risk factors were, do not tie belt at scaffold, falling stairways & ladders, exposure hazardous substances, tools & machinery, electricity (electric power accidents), repetitive tasks, the layout didn't consider health & safety aspects in the site, and do not provide safety orientation for new workers engaging the job. Employees are mostly affected on their lower body parts which needs more focus to prevent it, especially carpenter & roofers, plasterer and daily labors. Also the findings show that 50 % of respondents agree that the higher priority for safety and health management practices should be given to finishing part of the construction followed by excavation and earth work, masonry, and electrical installations. Therefore, it is recommended that the contractors must focus more on the finishing phase.

A Narrative Review of Fatigue in Agriculture and Its Impact on Injury and Fatality in Australia

OBJECTIVES

To identify current knowledge about the role of fatigue in occupational injury in the agricultural sector and briefly assess potential intervention approaches.

METHODS

Narrative review of peer reviewed literature (in English) from 2010 to 2022 focusing on fatigue in agricultural and other sectors. Data were extracted from Medline, Scopus, and Google Scholar.

RESULTS

The initial search revealed 6,031 papers, of these 33 met the inclusion criteria. The literature unanimously agreed that fatigue contributes to occupational injury in agriculture and related industries. However, there was a scarcity of literature specific to Australia or agriculture. This limits the ability to draw conclusions about the true relationship between fatigue and injury.

CONCLUSION

While fatigue is likely a major contributor to occupational injury in Australian agriculture, the limited literature impedes the ability to draw conclusions and extrapolate interventions used by other industries that are practical and feasible, to agriculture. Future studies should establish the nature of the problem in Australian agriculture and consult with members of the sector to establish the best interventions to ameliorate the problem, then implement and robustly evaluate intervention studies.

Evaluating Occupational Noise Exposure as a Contributor to Injury Risk among Miners

OBJECTIVES

This study: (i) assessed the relationship between noise exposure and injury risk, comprehensively adjusting for individual factors, psychosocial stressors, and organizational influences; (ii) determined the relative importance of noise on injuries; (iii) estimated the lowest observed adverse effect level (LOAEL) of noise on injury risk to determine the threshold of noise considered hazardous to injuries; and (iv) quantified the fraction of injuries that could be attributed to hazardous noise exposure.

METHODS

In this cross-sectional study at 10 US surface mine sites, traditional mixed effects, Poisson regression, and boosted regression tree (BRT) models were run on the number of reported work-related injuries in the last year. The LOAEL of noise on injuries was identified by estimating the percent increase in work-related injuries at different thresholds of noise exposure using a counterfactual estimator through the BRT model. A population attributable fraction (PAF) was quantified with this counterfactual estimator to predict reductions in injuries at the LOAEL.

RESULTS

Among 18 predictors of work-related injuries, mine site, perceived job safety, age, and sleepiness were the most important predictors. Occupational noise exposure was the seventh most important predictor. The LOAEL of noise for work-related injuries was a full-shift exposure of 88 dBA. Exposure ≥88 dBA was attributed to 20.3% (95% CI: 11.2%, 29.3%) of reported work-related injuries in the last year among the participants.

CONCLUSIONS

This study further supports hypotheses of a dose-response relationship between occupational noise exposure and work-related injuries, and suggests that exposures ≥88 dBA may increase injury risk in mining.

Ultra-processed food consumption and dietary, lifestyle and social determinants: a path analysis in Brazilian graduates (CUME project)

OBJECTIVE

To explore the relationship between ultra-processed foods (UPF) consumption and dietary, lifestyle and social determinants using pathway analysis in the baseline of the Cohort of Universities of Minas Gerais (CUME project).

DESIGN

Cross-sectional study, in which path analysis was used to estimate direct and indirect effects of dietary practices, sleep, time on the computer and professional status on UPF consumption.

SETTING

Data were collected in 2016, through an online questionnaire composed of sociodemographic, anthropometric, lifestyle and dietary practices questions, and a FFQ.

PARTICIPANTS

Baseline participants from the CUME Project (n 2826), adults who graduated from Universidade Federal de Viçosa or Universidade Federal de Minas Gerais, Brazil.

RESULTS

Being employed (P = 0·024), the time spent on the computer (P = 0·031) and the frequency of fried food intake (P < 0·001) were positively and directly associated with UPF consumption, whereas the sleep duration (P = 0·007) and the number of meals per d (P < 0·001) were negatively and directly associated with UPF consumption. Indirect effects were observed between being employed, mediated by the sleep duration (P = 0·032) and fried food intake (P = 0·005), whereas being a student is mediated by the time on the computer (P = 0·048).

CONCLUSION

The time spent on the computer, sleep duration and fried food consumption showed direct effects on UPF consumption. They also acted as mediators on the relationship between professional status and UPF consumption. Besides, the number of meals eaten each day also was directly associated with UPF consumption.

The Impact of Electroconvulsive Therapy on Negative Symptoms in Schizophrenia and Their Association with Clinical Outcomes

OBJECTIVE

The treatment efficacy of electroconvulsive therapy (ECT) for negative symptoms amongst patients with schizophrenia remains unclear. In this study, we aim to examine the effects of ECT on negative symptoms in schizophrenia and their association with other clinical outcomes, including cognition and function.

METHODS

This is a retrospective data analysis of patients with schizophrenia/schizoaffective disorder treated with ECT at the Institute of Mental Health (IMH), Singapore, between January 2016 and December 2019. Clinical outcomes were assessed by the Brief Psychiatric Rating Scale (BPRS), the Montreal Cognitive Assessment (MoCA), and Global Assessment of Function (GAF). Changes in scores were compared with repeated measures analysis of variance. Sequential structural modelling was utilized to examine the pathway relationships between changes in negative symptoms, global functioning, and cognition functioning after ECT.

RESULTS

A total of 340 patients were analysed. Hence, 196 (57.6%), 53 (15.5%), and 91 (26.7%) showed improvements, no change, and deterioration in negative symptoms, respectively. ECT-induced improvement of negative symptoms was significantly associated with improvement of global functioning (direct effect correlation coefficient (r): -0.496; se: 0.152; p = 0.001) and cognition function (indirect effect r: -0.077; se: 0.037; p = 0.035). Moreover, having capacity to consent, more severe baseline negative symptoms, lithium prescription, and an indirect effect of voluntary admission status via consent capacity predicted ECT associated negative symptoms improvement.

CONCLUSION

ECT is generally associated with improvements of negative symptoms in people with schizophrenia, which correlate with improvements of overall function. Possible novel clinical predictors of negative symptom improvement have been identified and will require further research and validation.

Precarious Work Schedules and Sleep: A Study of Unionized Full-Time Workers

Unlike precarious employment which is temporary and insecure, with inadequate pay, benefits, and legal protections, precarious work schedules can affect workers with permanent full-time jobs in sectors where employment has historically been secure, well-compensated, and even unionized. Precarious work schedules - characterized by long shifts, non-daytime hours, intensity and unsocial work hours - are increasingly prevalent. Relations between precarious work schedules and poor health are not well understood, and less is known about how to attenuate this relation. We examined the indirect effects of precarious work schedules on fatigue and depressive symptoms through sleep quantity. Two moderators - schedule flexibility and sleep quality - were examined as buffers of these associations. Workers from the Departments of Correction and Transportation in a northeast state (N = 222) took surveys and reported on demographics, work schedule characteristics, schedule flexibility, sleep quality and quantity, fatigue, and depressive symptoms. Results revealed that precarious work schedules had indirect effects on fatigue and depressive symptoms through sleep quantity. Schedule flexibility moderated the relation between precarious work schedules and sleep quantity, such that workers with greater schedule flexibility had more hours of sleep. Sleep quality moderated the association between sleep quantity and fatigue and depressive symptoms, such that workers reported greater fatigue and depressive symptoms when they had poorer sleep quality. Findings have direct applicability for developing initiatives that enhance Total Worker Health® through individual and organizational changes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41542-022-00114-y.

The Impact of Adverse Employment and Working Conditions on the Risk of Workplace Injury in Canada

Background

Employment standards (ES) include having a regular payday, regular breaks, the right to paid sick or vacation time, and paid wages. Inadequate ES contribute to the labour market vulnerability of workers; however, they are not typically considered to be risk factors for workplace injury. In a sample of Canadian workers, we examine the risk of injury associated with inadequate ES, independent of, and combined with inadequate workplace protections from workplace hazards.

Methods

Data from 2,803 adults working 15 hours or more/week in workplaces with at least five employees were analysed. We explored associations between exposure to workplace hazards with inadequate protections [termed occupational health and safety (OHS) vulnerability] and inadequate ES on workplace injury (physical or mental injury; injury requiring time off). Additive interaction models were used to examine the independent and combined effects of these exposures.

Results

Occupational health and safety vulnerability and inadequate ES were independently associated with increased injury outcomes. Adjusted models showed an additive relationship for all injury outcomes between OHS vulnerability and inadequate ES. Statistically significant superadditive relationships were observed for physical injury risk with policy and procedure vulnerability plus inadequate ES [synergy index (S) 1.50, 95% CI: 1.13-2.00] and for overall OHS vulnerability plus inadequate ES (S 1.53, 95% CI: 1.16-2.02), suggesting a combined effect greater than independent effects.

Conclusion

Occupational health and safety vulnerability and inadequate ES are independently associated with workplace injury. For certain injury outcomes, the combined effect of OHS vulnerability and inadequate ES is greater than the independent effects of each individual exposure.

Is burnout a mediating factor between sharps injury and work-related factors or musculoskeletal pain?

BACKGROUND

Burnout, musculoskeletal pain, and sharps injuries (SIs) affect medical workers.

AIM

To establish a model between SIs, burnout, and the risk factors to assess the extent to which burnout affects SIs.

METHODS

This questionnaire was used for an observational and cross-sectional study, which was based on members at a hospital affiliated with a medical university in Taichung, Taiwan, in 2020. The valid responses constituted 68.5% (1734 of 2531). The items were drawn from the Nordic Musculoskeletal Questionnaire and Copenhagen burnout inventory and concerned work experience, occupational category, presence of chronic diseases, sleep duration, overtime work, and work schedule. Factor analysis, chi-square test, Fisher exact test, Multiple linear, logistic regression and Sobel test were conducted. The present analyses were performed using SAS Enterprise Guide 6.1 software (SAS Institute Inc., Cary, NC, United States), and significance was set at P < 0.05.

RESULTS

Personal and work-related burnout ranks, sex, work experience ranks, occupational groups, drinking in the past month, sleep duration per day, presence of chronic diseases, overtime work ranks, and work schedule were associated with SIs. Frequent upper limb and lower limb pain (pain occurring every day or once a week) determined to be related to SIs. High personal burnout (> Q3) and high work-related burnout (> Q3) mediated the relationship between SIs and frequent lower limb pain. Similarly, frequent lower limb pain mediated the relationship of SIs with high personal and high work-related burnout. High personal and high work-related burnout mediated the relationships of SIs with overtime work and irregular shift work. The mediating model provides strong evidence of an association between mental health and SIs.

CONCLUSION

Burnout was determined to contribute to SIs occurrence; specifically, it mediated the relationships of SIs with frequent musculoskeletal pain, overtime work, and irregular shift work.

Decoding and comprehension skills mediate the link between a small-group reading programme and English national literacy assessments

BACKGROUND

Despite the fact that literacy instruction is a main focus of primary education, many children struggle to meet nationally set standards.

AIMS

We aimed to test which components of a comprehensive reading programme (ABRACADABRA: https://eur03.safelinks.protection.

OUTLOOK

com/?url=https%3A%2F%2Fdoi.org%2F10.1186%2FISRCTN18254678&data=04%7C01%7Cjanet.vousden%40ntu.ac.uk%7C880280e0b00749df855308d94068a0bb%7C8acbc2c5c8ed42c78169ba438a0dbe2f%7C1%7C0%7C637611640381216902%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=%2B4U9sGfofkyCPEY7lWz8n3TPoMOAeJMXyFwdhW6EpUw%3D&reserved=0) mediated the effect of the programme on nationally assessed literacy outcomes.

SAMPLE

Following blind allocation, 516 Year 1 pupils from 40 schools were randomized to the programme group, and 908 Year 1 pupils, to a control condition.

METHODS

Pupils in the programme completed 20 weeks of instruction in grapheme/phoneme knowledge, decoding, and comprehension. Control children received regular classroom instruction.

RESULTS

Children in the programme group were significantly better at these taught skills after the programme finished (effect sizes: grapheme/phoneme knowledge, β = .33, 95% CI [0.09-0.57]; decoding, β = .26, 95% CI [0.09-0.43]; and comprehension, β = .26, 95% CI [0.05-0.47]). Improvements in the programme group's decoding and comprehension skills fully mediated the improvements in national literacy assessments serving as a delayed post-test 12 months after the programme. Programme group pupils were 2.3 (95% CI [1.4-4.1]) times more likely to achieve/exceed the expected standard in reading, and 1.8 (95% CI [1.2-2.6]) times more likely to achieve/exceed the expected standard in writing due to an increase in the trained skills.

CONCLUSIONS

These results provide strong evidence that a programme that incorporates decoding and comprehension instruction for typically developing beginning readers improves distal educational outcomes in reading and writing through increasing proficiencies targeted by the reading programme.

A Generalized Structural Equation Model Approach to Long Working Hours and Near-Misses among Healthcare Professionals in Japan

(1) Background: Near-miss incidents are the foundation of major injuries. They are warning signs that loss is imminent. Long working hours are a risk factor for near-misses along with sleep problems, job-related stress, and depressive symptoms. This study aimed to evaluate the indirect effects of long working hours via mediating variables on near-miss occurrences among Japanese healthcare professionals. (2) Methods: 1490 Japanese healthcare professionals’ reports from a web-based survey of workers in October 2018 were analyzed to evaluate total, direct, and indirect effects of long working hours on near-misses. We applied a generalized structural equation model with three mediating variables: sleep problems, job-related stress, and depressive symptoms. (3) Results: The total effect and direct effect of the categories of working hours longer than 41 h per week (h/w) for occurrence of near-misses were not significantly higher than that of 35–40 h/w. However, for indirect effects on occurrence of near-misses that first passed through job-related stress, there were higher reports for each category compared to 35–40 h/w, with odds ratios (OR) and 95% confidence intervals (95% CI) of OR = 1.12, 95% CI (1.07, 1.21) for 41–50 h/w; 1.25, (1.14, 1.41) for 51–60 h/w; and 1.31, (1.18, 1.51) for ≥ 61 h/w. (4) Conclusion: The results suggest that reducing working hours might improve job-related stress, which could reduce near-misses and prevent injuries.

Parallel Assessment Challenges in Nutritional and Sleep Epidemiology

Sleep has been consistently linked to health outcomes in clinical studies, but only in recent years has sleep become a focus in epidemiologic studies and public health. In particular, the sizable prevalence of insufficient sleep in the population warrants well-designed epidemiologic studies to examine its impact on public health. As a developing field, sleep epidemiology encounters methodological challenges similar to those faced by nutritional epidemiology research. In this article, we describe a few central challenges related to assessment of sleep duration in population-based studies in comparison with measurement challenges in nutritional epidemiology. In addition, we highlight 3 strategies applied in nutritional epidemiology to address measurement challenges and suggest ways these strategies could be implemented in large-scale sleep investigations.

Fatigue and the Need for Recovery among Latino/a Immigrant Cattle Feedyard Workers

Cattle feedyards are animal feeding operations where beef cattle are finished to market weight on grain. Cattle feeding can be dirty, demanding, and dangerous work. This study sought to assess the predictors of fatigue and the need for recovery among Latino/a immigrant cattle feedyard workers in the United States. A path model was examined to explore direct and indirect relations among physical fatigue, mental fatigue, need for recovery, job characteristics, and health and sociodemographic covariates. Lower self-reported health, experiencing physical pain, not handling animals, and decreased decision latitude were directly related to increased physical fatigue. Shorter tenure working on cattle feedyards, lower educational level, experiencing physical pain, and increased job demands were directly related to heightened mental fatigue. Being female, experiencing physical pain, an elevated average of hours worked per day, increased job demands, and less decision latitude were directly related to an increased need for recovery and indirectly related to both physical and mental fatigue. Physical and mental fatigue have specific correlates, but job characteristics, including job demands and decision latitude, can directly and indirectly impact workers' levels of physical and mental fatigue and their need for recovery. Both preventive measures and restructuring work operations may reduce the risk for fatigue and the need for recovery. Implications for cattle feedyard workers, supervisors, and employers are discussed. Finding ways to balance productivity and the well-being of workers should be a high priority for cattle feedyards across the country.

Changes in the levels of IL-1β, cortisol and chromogranin A in saliva of subjects with occupational fatigue

Changes in the levels of interleukin-1β (IL-1β), cortisol and chromogranin A (CgA) in saliva of subjects with occupational fatigue were investigated. Doctors in the Emergency Department were selected as research subjects. Saliva was collected before work (after full rest) and after work (≥24 h). Electroencephalogram (EEG) was performed. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of IL-1β, cortisol and CgA in saliva. In order to obtain permission for human specimens, the study was approved by the Ethics Committee of the Affiliated Hospital of Hebei University of Engineering and registered for clinical trials (registration no. ChiC-TR-DCD-14005746). As there were only 4 subjects in this study without fatigue waves in EEG, and the number of these subjects was not sufficient to constitute a control group, the comparison of the contents of IL-1β, cortisol and CgA of all subjects before and after working for 18 h was just a confirmation of the statistical results of 43 cases with fatigue waves in the EEG. According to the results, there was no change in the contents of IL-1β and cortisol in the saliva of subjects with occupational fatigue before and after fatigue, whereas, there was a significant change in the content of CgA before and after fatigue. However, there was no correlation between the content of CgA and fatigue. The results of the present study revealed that IL-1β, cortisol and CgA indicators are not suitable diagnostic markers for occupational fatigue.

Longitudinal association between near-misses/minor injuries and moderate/severe injuries in industrial settings by presence/absence of depressive symptoms in a nationally representative sample of workers in Japan

OBJECTIVES

The association between near-misses/minor injuries and moderate/severe injuries has yet to be investigated longitudinally. This study aimed to examine the longitudinal association between near-misses/minor injuries and moderate/severe injuries by the presence/absence of depressive symptoms using 1-year follow-up data obtained from a nationally representative sample of workers in Japan.

METHODS

Of the 18 231 eligible participants at time 1 (T1), 12 127 who responded to the 1-year follow-up survey at time 2 (T2) (response rate: 66.5%; 4370 females and 7757 males; mean age (SD), 45.3 (10.5) years) were included in the analysis. Multivariate logistic regression analyses were performed with the presence/absence of moderate/severe injuries at T2 as the dependent variable.

RESULTS

In total, 36.4% of participants reported depressive symptoms at T1. During the follow-up period, 1.6% of participants reported moderate/severe injuries in industrial settings. After adjusting for relevant variables, participants who reported near-misses (OR=1.7 (95% CI, 1.3 to 2.4)) and minor injuries (OR=2.5 (95% CI, 1.3 to 4.7)) at T1 were more likely to have moderate/severe injuries at T2 compared to those who reported no near-misses/minor injuries. However, this association was stronger in participants who did not have depressive symptoms at T1 than in those who had depressive symptoms.

CONCLUSIONS

While the predictive value of near-misses/minor injuries for the occurrence of moderate/severe injuries by the presence/absence of depressive symptoms should be cautiously interpreted, our findings suggest that the development and utilisation of near-miss/minor injury reporting systems may help reduce the likelihood of moderate/severe injuries among workers, especially those without depressive symptoms.

Cervical musculoskeletal disorders and their relationships with personal and work-related factors among electronic assembly workers

INTRODUCTION

Electronics assembly workers are reported to have a high prevalence of musculoskeletal disorders (MSDs). This study investigated the prevalence of cervical MSDs and the complex relationships between cervical MSDs and individual, physical, psychosocial factors among electronics assembly workers.

METHODS

In this cross-sectional survey, self-administered questionnaires from 700 workers in electronics manufacturing workshops were analysed. Information concerning musculoskeletal symptoms, personal and work-related factors was collected. Finally, the prevalence of cervical MSDs was computed for different subgroups, and the relationships with different factors were analyzed using logistic regression and structural equation modeling (SEM).

RESULTS

The total 12 month prevalence of cervical MSDs among the survey population was 29.4%. Variables of gender, job tenure, twisting head frequently, neck flexion/extension for long time and work required to be done quickly showed significant associations with MSDs in a multivariate logistic regression (P < 0.05). The SEM analysis showed moderate and significant correlations between postural load (γ = 0.279), gender (γ = 0.233) and cervical MSDs, while there were weak but significant correlations between vibration (γ = 0.024), work stress (γ = 0.126), job tenure (γ = 0.024) and cervical MSDs. Both work stress and vibration affected the MSDs indirectly through postural load.

CONCLUSIONS

The logistic regression results support previous general epidemiological MSD studies, and indicates that individual, physical, and psychosocial factors are related to cervical MSDs. The SEM provides a better approximation of the complexity of the relationship between risk factors and cervical MSDs. Improving awkward postures may be effective ways to control the influence of occupational stressors or vibration on MSDs. Practical Applications: The study is to improve prevention of MSDs among electronics assembly workers and promote their occupational health.

Reoccurring Injury, Chronic Health Conditions, and Behavioral Health: Gender Differences in the Causes of Workers' Compensation Claims

OBJECTIVE

The aim of this study was o examine how work and nonwork health-related factors contribute to workers' compensation (WC) claims by gender.

METHODS

Workers (N = 16,926) were enrolled in the Pinnacol Assurance Health Risk Management study, a multiyear, longitudinal research program assessing small and medium-sized enterprises in Colorado. Hypotheses were tested using gender-stratified logistic regression models.

RESULTS

For both women and men, having incurred a prior WC claim increased the odds of a future claim. The combination of incurring a prior claim and having metabolic health conditions resulted in lower odds of a future claim. Behavioral health risk factors increased the odds of having a claim more so among women than among men.

CONCLUSION

This study provides data to support multifactorial injury theories, and the need for injury prevention efforts that consider workplace conditions as well as worker health.

Investigating daily fatigue scores during two-week offshore day shifts

OBJECTIVES

This study examined daily scores of fatigue and circadian rhythm markers over two-week offshore day shift periods.

METHODS

A prospective cohort study among N = 60 offshore day-shift workers working two-week offshore shifts was conducted. Offshore day shifts lasted from 07:00 - 19:00 h. Fatigue was measured objectively with pre- and post-shift scores of the 3-minute psychomotor vigilance tasks (PVT-B) parameters (reaction times, number of lapses, errors and false starts) and subjectively with pre- and post-shift Karolinska Sleepiness Scale (KSS) ratings. Evening saliva samples were collected on offshore days 2,7 and 13 to measure circadian rhythm markers such as dim-light melatonin onset times and cortisol. Generalized and linear mixed model analyses were used to examine daily fatigue scores over time.

RESULTS

Complete data from N = 42 offshore day shift workers was analyzed. Daily parameters of objective fatigue, PVT-B scores (reaction times, average number of lapses, errors and false starts), remained stable over the course of the two-week offshore day shifts. Daily subjective post-shift fatigue scores significantly increased over the course of the two-week offshore shifts. Each day offshore was associated with an increased post-shift subjective fatigue score of 0.06 points (95%CI: .03 - .09 p < .001). No significant statistical differences in subjective pre-shift fatigue scores were found. Neither a circadian rhythm phase shift of melatonin nor an effect on the pattern and levels of evening cortisol was found.

CONCLUSION

Daily parameters of objective fatigue scores remained stable over the course of the two-week offshore day shifts. Daily subjective post-shift fatigue scores significantly increased over the course of the two-week offshore shifts. No significant changes in circadian rhythm markers were found. Increased post-shift fatigue scores, especially during the last days of an offshore shift, should be considered and managed in (offshore) fatigue risk management programs and fatigue risk prediction models.

The incidence and burden of time loss injury in Australian men's sub-elite football (soccer): A single season prospective cohort study

OBJECTIVES

This study aimed to conduct the first injury surveillance study in sub-elite football in Australia, using methods from the international football consensus statement.

DESIGN

Descriptive epidemiological study.

METHODS

1049 sub-elite football players were recruited during the 2016 season. Injury and exposure data was collected by trained Primary Data Collectors (PDCs) who attended every training session and match.

RESULTS

There were 1041 time loss injuries recorded during 52,127h of exposure resulting in an injury incidence rate of 20 injuries/1000h (95% Confidence Interval [CI]: 15.9-23.3). The injury burden (days lost to injury relative to exposure) was 228days lost/1000h. Muscle and ligament injuries were the most prevalent (41% and 26%) and incurred the highest injury burden (83 and 80days lost/1000h, respectively). The most common injuries were observed at the thigh (22%) and ankle (17%), with hamstring (13%) the highest reported muscle injury. The profile of injury severity was: mild - 35%; minor - 29%; moderate - 28% and severe - 8%. Recurrent injuries accounted for 20% of all injuries.

CONCLUSIONS

By addressing issues identified with injury recording in sub-elite football, this study found that the injury incidence was twice that observed in previous research in elite and sub-elite football cohorts. Injury burden was also twice that of the elite setting, with similar injuries associated with the highest burden. The results highlight the need for investment into medical provision, facilities, coach education and injury mitigation programmes to reduce healthcare costs to sub-elite players in Australia.

Examining courses of sleep quality and sleepiness in full 2 weeks on/2 weeks off offshore day shift rotations

To better understand sleep quality and sleepiness problems offshore, we examined courses of sleep quality and sleepiness in full 2-weeks on/2-weeks off offshore day shift rotations by comparing pre-offshore (1 week), offshore (2 weeks) and post-offshore (1 week) work periods. A longitudinal observational study was conducted among N=42 offshore workers. Sleep quality was measured subjectively with two daily questions and objectively with actigraphy, measuring: time in bed (TIB), total sleep time (TST), sleep latency (SL) and sleep efficiency percentage (SE%). Sleepiness was measured twice a day (morning and evening) with the Karolinska Sleepiness Scale. Changes in sleep and sleepiness parameters during the pre/post and offshore work periods were investigated using (generalized) linear mixed models. In the pre-offshore work period, courses of SE% significantly decreased (p=.038). During offshore work periods, the courses of evening sleepiness scores significantly increased (p<.001) and significantly decreased during post-offshore work periods (p=.004). During offshore work periods, TIB (p<.001) and TST (p<.001) were significantly shorter, SE% was significantly higher (p=.002), perceived sleep quality was significantly lower (p<.001) and level of rest after wake was significantly worse (p<.001) than during the pre- and post-offshore work periods. Morning sleepiness was significantly higher during offshore work periods (p=.015) and evening sleepiness was significantly higher in the post-offshore work period (p=.005) compared to the other periods. No significant changes in SL were observed. Courses of sleep quality and sleepiness parameters significantly changed during full 2-weeks on/2-weeks off offshore day shift rotation periods. These changes should be considered in offshore fatigue risk management programmes.

Risk of work injury among adolescent students from single and partnered parent families

BACKGROUND

Parental involvement in keeping their children safe at work has been examined in a handful of studies, with mixed results. Evidence has suggested that non-work injury risk is higher among children from single-parent families, but little is known about their risk for work-related injuries.

METHODS

Five survey cycles of the Canadian Community Health Survey were pooled to create a nationally representative sample of employed 15-19-year old students (N = 16,620). Multivariable logistic regression estimated the association between family status and work injury.

RESULTS

Risk of work-related repetitive strains (OR:1.24, 95%CI: 0.69-2.22) did not differ by family type. However, children of single parents were less likely to sustain a work injury receiving immediate medical care (OR:0.43, 95%CI: 0.19-0.96).

CONCLUSION

Despite advantages and disadvantages related to family types, there is no evidence that work-related injury risk among adolescents from single parent families is greater than that of partnered-parent families. Am. J. Ind. Med. 60:285-294, 2017. © 2017 Wiley Periodicals, Inc.

Mediating pathways and gender differences between shift work and subjective cognitive function

OBJECTIVES

Increased injury risk among shift workers is often attributed to cognitive function deficits that come about as a result of sleep disruptions. However, little is known about the intermediate influences of other factors (eg, work stress, health) which may affect this relationship. In addition, gender differences in these the complex relationships have not been fully explored. The purpose of this study is to (1) identify the extent to which work and non-work factors mediate the relationship between shift work, sleep and subsequent subjective cognitive function; and (2) determine if the mediating pathways differ for men and women.

METHODS

Data from the 2010 National Population Health Survey was used to create a cross-sectional sample of 4255 employed Canadians. Using path modelling, we examined the direct and indirect relationships between shift work, sleep duration, sleep quality and subjective cognitive function. Multigroup analyses tested for significantly different pathways between men and women. Potential confounding effects of age and self-reported health and potential mediating effects of work stress were simultaneously examined.

RESULTS

Work stress and sleep quality significantly mediated the effects of shift work on cognition. Age and health confounded the relationship between sleep quality and subjective cognition. No differences were found between men and women.

CONCLUSIONS

Occupational health and safety programmes are needed to address stress and health factors, in addition to sleep hygiene, to effectively address cognitive function among shift workers.

Substance Use as a Mediator of the Association Between Demographics, Suicide Attempt History, and Future Suicide Attempts in Emergency Department Patients

BACKGROUND

Identification of factors that predict and protect against attempted suicide are critical for the development of effective suicide prevention and intervention programs.

AIMS

To examine whether substance use mediates the association between demographic characteristics, suicide attempt history, and reports of a suicide attempt within 12 months after screening positive for active suicidal ideation or behavior during the index emergency department (ED) visit.

METHOD

Data were collected during the first two phases of the Emergency Department Safety Assessment and Follow-up Evaluation (ED-SAFE) study. Data collection included baseline interview; 6- and 12-month chart reviews; and 6-, 12-, 24-, 36-, and 52-week telephone follow-up assessments. Structural equation modeling was used. All p values were two-tailed, with p < .05 considered statistically significant.

RESULTS

Among the 874 subjects, 195 (22%) reported a suicide attempt within 12 months after the index ED visit. Of participants reporting a suicide attempt, 59% were < 40 years old, 59% female, and 76% non-Hispanic White. Associations between race, sex, and suicide attempt 12 months after the index ED visit may be mediated by a combination of alcohol misuse and cocaine use.

CONCLUSION

Findings from the mediation analyses provide insight into the impact of substance use on future suicide attempts in various sociodemographic groups.

Development of the National Healthy Sleep Awareness Project Sleep Health Surveillance Questions

OBJECTIVES

For the first time ever, as emphasized by inclusion in the Healthy People 2020 goals, sleep health is an emphasis of national health aims. The National Healthy Sleep Awareness Project (NHSAP) was tasked to propose questions for inclusion in the next Behavioral Risk Factor Surveillance System (BRFSS), a survey that includes a number of questions that target behaviors thought to impact health, as a means to measure community sleep health. The total number of questions could not exceed five, and had to include an assessment of the risk for obstructive sleep apnea (OSA).

METHODS

An appointed workgroup met via teleconference and face-to-face venues to develop an inventory of published survey questions being used to identify sleep health, to develop a framework on which to analyze the strengths and weaknesses of current survey questions concerning sleep, and to develop recommendations for sleep health and disease surveillance questions going forward.

RESULTS

The recommendation was to focus on certain existing BRFSS questions pertaining to sleep duration, quality, satisfaction, daytime alertness, and to add to these other BRFSS existing questions to make a modified STOP-BANG questionnaire (minus the N for neck circumference) to assess for risk of OSA.

CONCLUSIONS

Sleep health is an important dimension of health that has previously received less attention in national health surveys. We believe that 5 questions recommended for the upcoming BRFSS question banks will assist as important measures of sleep health, and may help to evaluate the effectiveness of interventions to improve sleep health in our nation.

Associations of Individual-Related and Job-Related Risk Factors with Nonfatal Occupational Injury in the Coal Workers of Shanxi Province: A Cross-Sectional Study

OBJECTIVES

To assess the relationships between the risk factors and the incidence of nonfatal occupational injury of coal mine workers of Shanxi Province.

METHODS

A cross-sectional study was conducted from July 2013 to December 2013, and 4319 workers were recruited from more than 200,000 coal mine employees who are exposed to continuous potential risk of occupational injuries by using a two-stage stratified cluster sampling method. Trained interviewers having necessary medical knowledge conducted face-to-face interviews with the participants. Univariate and multivariable logistic regression models were used to estimate the odds ratio (OR) and the 95% confidence interval (CI).

RESULTS

A total number of 3618 effective respondents were got from 4319 participants (83.77%) and the mean age of the participants was 41.5 years with the standard deviation of 8.65. Significant crude odds ratios were observed for all factors considered except for marital status, education, work duration, BMI, EPQ-RSC(P) scale and EPQ-RSC(L) scale. Results from multivariable logistic regression model showed significant adjusted odds ratios for risk factors including gender (female vs male 0.275, 0.094-0.800), age (≥55 vs ≤25yr 0.169, 0.032-0.900), work type (light physical labor vs heavy physical labor 0.504, 0.328-0.774), workplace (underground auxiliary vs underground front-line 0.595, 0.385-0.919), length of shiftwork experience (0~5yr vs no shift 2.075, 1.287-3.344 and ≥15yr vs no shift 2.076, 1.230-3.504) and EPQ-RSC(E) score (extraversion vs introversion 0.538, 0.334-0.867).

CONCLUSIONS

Several risk factors of nonfatal occupational injury were identified including male, age, heavy physical labor, underground front-line, length of shiftwork experience and introversion. The coal mining enterprises should pay attention to controlling the hazards associated with frontline physical work. Workers' behaviors, life styles and personality traits should also be considered, so that the enterprises could set achievable targets for workers and lessen the exposed period to the risky underground workstation.

Associations of Individual-Related and Job-Related Risk Factors with Nonfatal Occupational Injury in the Coal Workers of Shanxi Province: A Cross-Sectional Study

OBJECTIVES

To assess the relationships between the risk factors and the incidence of nonfatal occupational injury of coal mine workers of Shanxi Province.

METHODS

A cross-sectional study was conducted from July 2013 to December 2013, and 4319 workers were recruited from more than 200,000 coal mine employees who are exposed to continuous potential risk of occupational injuries by using a two-stage stratified cluster sampling method. Trained interviewers having necessary medical knowledge conducted face-to-face interviews with the participants. Univariate and multivariable logistic regression models were used to estimate the odds ratio (OR) and the 95% confidence interval (CI).

RESULTS

A total number of 3618 effective respondents were got from 4319 participants (83.77%) and the mean age of the participants was 41.5 years with the standard deviation of 8.65. Significant crude odds ratios were observed for all factors considered except for marital status, education, work duration, BMI, EPQ-RSC(P) scale and EPQ-RSC(L) scale. Results from multivariable logistic regression model showed significant adjusted odds ratios for risk factors including gender (female vs male 0.275, 0.094-0.800), age (≥55 vs ≤25yr 0.169, 0.032-0.900), work type (light physical labor vs heavy physical labor 0.504, 0.328-0.774), workplace (underground auxiliary vs underground front-line 0.595, 0.385-0.919), length of shiftwork experience (0~5yr vs no shift 2.075, 1.287-3.344 and ≥15yr vs no shift 2.076, 1.230-3.504) and EPQ-RSC(E) score (extraversion vs introversion 0.538, 0.334-0.867).

CONCLUSIONS

Several risk factors of nonfatal occupational injury were identified including male, age, heavy physical labor, underground front-line, length of shiftwork experience and introversion. The coal mining enterprises should pay attention to controlling the hazards associated with frontline physical work. Workers' behaviors, life styles and personality traits should also be considered, so that the enterprises could set achievable targets for workers and lessen the exposed period to the risky underground workstation.

Modeling contextual effects using individual-level data and without aggregation: an illustration of multilevel factor analysis (MLFA) with collective efficacy

Population health scientists increasingly study how contextual-level attributes affect individual health. A major challenge in this domain relates to measurement, i.e., how best to measure and create variables that capture characteristics of individuals and their embedded contexts. This paper presents an illustration of multilevel factor analysis (MLFA), an analytic method that enables researchers to model contextual effects using individual-level data without using derived variables. MLFA uses the shared variance in sets of observed items among individuals within the same context to estimate a measurement model for latent constructs; it does this by decomposing the total sample variance-covariance matrix into within-group (e.g., individual-level) and between-group (e.g., contextual-level) matrices and simultaneously modeling distinct latent factor structures at each level. We illustrate the MLFA method using items capturing collective efficacy, which were self-reported by 2,599 adults in 65 census tracts from the Los Angeles Family and Neighborhood Survey (LAFANS). MLFA identified two latent factors at the individual level and one factor at the neighborhood level. Indicators of collective efficacy performed differently at each level. The ability of MLFA to identify different latent factor structures at each level underscores the utility of this analytic tool to model and identify attributes of contexts relevant to health.

Reduced sleep duration and history of work-related injuries among Washington State adolescents with a history of working

BACKGROUND

The relationship between sleep and occupational injury risk has not been adequately explored for working adolescents.

METHODS

Data were analyzed from the 2010 Washington State Healthy Youth Survey of 8th, 10th, and 12th grade public school students. Teens reported average school and weekend night sleep hours and history of work-related injury that received medical treatment. Multivariable logistic regression evaluated the association between sleep duration and occupational injury.

RESULTS

Of 4,144 working teens, 6.4% reported ever having an occupational injury. Teens who sleep ≤5 hr/school night had greater odds of a history of occupational injury than those sleeping 8 hr (OR:2.91, 95% CI:1.85-4.57). No significant association was observed for weekend night sleep duration.

CONCLUSIONS

Reduced school night sleep was associated with increased odds of work-related injury in adolescents. Long hours and late night schedules may contribute to decreased sleep time and potentially have other health and developmental impacts for youth.

Does tinnitus, hearing asymmetry, or hearing loss predispose to occupational injury risk?

OBJECTIVE

To determine the relative contributions of tinnitus, asymmetrical hearing loss, low frequency hearing loss (pure tone average of 0.5, 1, 2, 3 kHz; PTA.5123), or high frequency hearing loss (pure tone average of 4, 6 kHz; PTA46), to acute injury risk among a cohort of production and maintenance workers at six aluminum manufacturing plants, adjusting for ambient noise exposure and other recognized predictors of injury risk.

DESIGN

Retrospective analysis.

STUDY SAMPLE

The study considered 9920 workers employed during 2003 to 2008. The cohort consisted of 8818 workers (89%) whose complete records were available.

RESULTS

Adjusting for noise exposure and other recognized injury predictors, a 25% increased acute injury risk was observed among workers with a history of tinnitus in conjunction with high-frequency hearing loss (PTA46). Low frequency hearing loss may be associated with minor, yet less serious, injury risk. We did not find evidence that asymmetry contributes to injury risk.

CONCLUSION

These results provide evidence that tinnitus, combined with high-frequency hearing loss, may pose an important safety threat to workers, especially those who work in high-noise exposed environments. These at risk workers may require careful examination of their communication and hearing protection needs.

Psychological distress and pain reporting in Australian coal miners

Background

Coal mining is of significant economic importance to the Australian economy. Despite this fact, the related workforce is subjected to a number of psychosocial risks and musculoskeletal injury, and various psychological disorders are common among this population group. Because only limited research has been conducted in this population group, we sought to examine the relationship between physical (pain) and psychological (distress) factors, as well as the effects of various demographic, lifestyle, and fatigue indicators on this relationship.

Methods

Coal miners (N = 231) participated in a survey of musculoskeletal pain and distress on-site during their work shifts. Participants also provided demographic information (job type, age, experience in the industry, and body mass index) and responded to questions about exercise and sleep quality (on- and off-shift) as well as physical and mental tiredness after work.

Results

A total of 177 workers (80.5%) reported experiencing pain in at least one region of their body. The majority of the sample population (61.9%) was classified as having low-level distress, 28.4% had scores indicating mild to moderate distress, and 9.6% had scores indicating high levels of distress. Both number of pain regions and job type (being an operator) significantly predicted distress. Higher distress score was also associated with greater absenteeism in workers who reported lower back pain. In addition, perceived sleep quality during work periods partially mediated the relationship between pain and distress.

Conclusion

The study findings support the existence of widespread musculoskeletal pain among the coal-mining workforce, and this pain is associated with increased psychological distress. Operators (truck drivers) and workers reporting poor sleep quality during work periods are most likely to report increased distress, which highlights the importance of supporting the mining workforce for sustained productivity.

Sleep quality and the risk of work injury: a Swiss case-control study

Sleep problems are a well-known risk factor for work injuries, but less is known about which vulnerable populations are most at risk. The aims of this study were to investigate the association between sleep quality and the risk of work injury and to identify factors that may modify the association. A case-control study including 180 cases and 551 controls was conducted at the University Hospital in Basel, Switzerland, from 1 December 2009 to 30 June 2011. Data on work injuries and sleep quality were collected. Adjusted odds ratios and 95% confidence intervals of the association between sleep quality and work injury were estimated in multivariable logistic regression analyses and were stratified by hypothesized effect modifiers (age, gender, job risk, shift work, sleep duration and working hours). Poor sleep quality was associated significantly with work injury of any type (P < 0.05) and with being caught in particular (P < 0.05). The association between poor sleep quality and work injury was significantly higher for workers older than 30 years (odds ratio>30 1.30 versus odds ratio≤30 0.91, P < 0.01), sleeping 7 h or less per night (odds ratio≤7 1.17 versus odds ratio>7 0.79, P < 0.05) and working 50 h or more per week (odds ratio≥50 1.79 versus odd ratio<50 1.10, P < 0.01). Work injury risk increased with increasing severity of sleep problems (P < 0.05). Prior work injury frequency increased with decreasing sleep quality (P < 0.05). Older age, short sleep duration and long working hours may enhance the risk of work injuries associated with sleep quality.

Body mass index and the risk of injury in adults: a cross-sectional study

OBJECTIVES

To investigate the association between body mass index (BMI) and the risk of nonfatal body injury.

METHODS

We analyzed data from 113,203 adults who participated in the Canadian Community Health Survey conducted in 2009-2010. Log-binomial models were used to estimate crude and adjusted relative risks of the association between BMI and the risk of body injury for men and women.

RESULTS

Of 113,203 adult participants, 15,194 had self-reported body injuries during the past 12 months, with a 12-month cumulative incidence of 13.7% (weighted to Canadian population). There was a significant interaction between gender and BMI in relation to the risk of body injury, and therefore, analyses were stratified by gender. For women, we found a significant association between BMI and an increased risk of body injury. Women with an increased BMI had a significant increased risk of body injuries as compared with those with normal weight (adjusted relative risk: 1.13, 95% confidence interval (CI)=1.02-1.25 for BMI 30.0-34.9 kg m(-)(2); 1.17, 95% CI=1.00-1.37 for BMI 35.0-39.9 kg m(-)(2); 1.41, 95% CI=1.16-1.69 for BMI ⩾ 40 kg m(-)(2)). A reduced risk of injury was observed in underweight women. There was no significant association between BMI and the risk of body injury for men. Obese persons of both gender were more likely to suffer injuries to the knee and lower leg, and in less demanding activities such as household chores or using the stairs.

CONCLUSIONS

We therefore conclude that increased BMI may be a risk factor for body injury in women, but not in men.

Work in multiple jobs and the risk of injury in the US working population

OBJECTIVES

We compared the risk of injury for multiple job holders (MJHs) with that for single job holders (SJHs).

METHODS

We used information from the National Health Interview Survey for the years 1997 through 2011 to estimate the rate of multiple job holding in the United States and compared characteristics and rates of self-reported injury (work and nonwork) for SJHs versus MJHs.

RESULTS

Approximately 8.4% of those employed reported working more than 1 job in the week before the interview. The rate of work and nonwork injury episodes per 100 employed workers was higher for MJHs than for SJHs (4.2; 95% confidence interval [CI] = 3.5, 4.8; vs 3.3; 95% CI = 3.1, 3.5 work injuries and 9.9; 95% CI = 8.9, 10.9; vs 7.4; 95% CI = 7.1, 7.6 nonwork injuries per 100 workers, respectively). When calculated per 100 full-time equivalents (P < .05), the rate ratio remained higher for MJHs.

CONCLUSIONS

Our findings suggest that working in multiple jobs is associated with an increased risk of an injury, both at work and not at work, and should be considered in injury surveillance.

Occupational burnout and severe injuries: an eight-year prospective cohort study among Finnish forest industry workers

OBJECTIVES

Burnout is a psychological consequence of prolonged work stress. Studies have shown that it is related to physical and mental disorders. The safety outcomes of burnout have been studied to a lesser extent and only in the work context. This study explored the effect of burnout on future severe injuries regardless of their context.

METHODS

A total of 10,062 forest industry employees (77% men, 63% manual workers) without previous injuries participated in 1996 or 2000 in the "Still Working" study examining the work-related antecedents of health and mortality. Burnout was assessed using the Maslach Burnout Inventory-General Survey. Injuries leading to death or hospitalization were regarded as severe. We extracted such injuries from independent national registers. The relationship between burnout and new injuries was analyzed using Cox proportional regression. The analyses were adjusted for age, sex, marital status, and occupational status.

RESULTS

There were 788 new injuries over eight years. Injuries were more common among male and manual workers. After adjustments, each one-unit increase in the burnout score was related to a 9% increase in the risk of injury (95% confidence interval: 1.2-1.17). Experiencing symptoms at least monthly was related to a 1.18-fold adjusted injury risk (95% CI: 1.2-1.36). Of the subscales of burnout, exhaustion and cynicism but not lack of professional efficacy predicted injuries after adjustments.

CONCLUSIONS

In addition to mental and physical disorders, burnout predicts severe injuries. Developing work conditions and optimizing workload may enhance safety and decrease health expenses related to all injuries.

Association between In Utero arsenic exposure, placental gene expression, and infant birth weight: a US birth cohort study

BACKGROUND

Epidemiologic studies and animal models suggest that in utero arsenic exposure affects fetal health, with a negative association between maternal arsenic ingestion and infant birth weight often observed. However, the molecular mechanisms for this association remain elusive. In the present study, we aimed to increase our understanding of the impact of low-dose arsenic exposure on fetal health by identifying possible arsenic-associated fetal tissue biomarkers in a cohort of pregnant women exposed to arsenic at low levels.

METHODS

Arsenic concentrations were determined from the urine samples of a cohort of 133 pregnant women from New Hampshire. Placental tissue samples collected from enrollees were homogenized and profiled for gene expression across a panel of candidate genes, including known arsenic regulated targets and genes involved in arsenic transport, metabolism, or disease susceptibility. Multivariable adjusted linear regression models were used to examine the relationship of candidate gene expression with arsenic exposure or with birth weight of the baby.

RESULTS

Placental expression of the arsenic transporter AQP9 was positively associated with maternal urinary arsenic levels during pregnancy (coefficient estimate: 0.25; 95% confidence interval: 0.05 - 0.45). Placental expression of AQP9 related to expression of the phospholipase ENPP2 which was positively associated with infant birth weight (coefficient estimate: 0.28; 95% CI: 0.09 - 0.47). A structural equation model indicated that these genes may mediate arsenic's effect on infant birth weight (coefficient estimate: -0.009; 95% confidence interval: -0.032 - -0.001; 10,000 replications for bootstrapping).

CONCLUSIONS

We identified the expression of AQP9 as a potential fetal biomarker for arsenic exposure. Further, we identified a positive association between the placental expression of phospholipase ENPP2 and infant birth weight. These findings suggest a path by which arsenic may affect birth outcomes.

Invited commentary: structural equation models and epidemiologic analysis

In this commentary, structural equation models (SEMs) are discussed as a tool for epidemiologic analysis. Such models are related to and compared with other analytic approaches often used in epidemiology, including regression analysis, causal diagrams, causal mediation analysis, and marginal structural models. Several of these other approaches in fact developed out of the SEM literature. However, SEMs themselves tend to make much stronger assumptions than these other techniques. SEMs estimate more types of effects than do these other techniques, but this comes at the price of additional assumptions. Many of these assumptions have often been ignored and not carefully evaluated when SEMs have been used in practice. In light of the strong assumptions employed by SEMs, the author argues that they should be used principally for the purposes of exploratory analysis and hypothesis generation when a broad range of effects are potentially of interest.