Risk assessments using the Strain Index and the TLV for HAL, Part II: Multi-task jobs and prevalence of CTS.

The Strain Index (SI) and the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value for hand activity level (TLV for HAL) have been shown to be associated with prevalence of distal upper-limb musculoskeletal disorders such as carpal tunnel syndrome (CTS). The SI and TLV for HAL disagree on more than half of task exposure classifications. Similarly, time-weighted average (TWA), peak, and typical exposure techniques used to quantity physical exposure from multi-task jobs have shown between-technique agreement ranging from 61% to 93%, depending upon whether the SI or TLV for HAL model was used. This study compared exposure-response relationships between each model-technique combination and prevalence of CTS. Physical exposure data from 1,834 workers (710 with multi-task jobs) were analyzed using the SI and TLV for HAL and the TWA, typical, and peak multi-task job exposure techniques. Additionally, exposure classifications from the SI and TLV for HAL were combined into a single measure and evaluated. Prevalent CTS cases were identified using symptoms and nerve-conduction studies. Mixed effects logistic regression was used to quantify exposure-response relationships between categorized (i.e., low, medium, and high) physical exposure and CTS prevalence for all model-technique combinations, and for multi-task workers, mono-task workers, and all workers combined. Except for TWA TLV for HAL, all model-technique combinations showed monotonic increases in risk of CTS with increased physical exposure. The combined-models approach showed stronger association than the SI or TLV for HAL for multi-task workers. Despite differences in exposure classifications, nearly all model-technique combinations showed exposure-response relationships with prevalence of CTS for the combined sample of mono-task and multi-task workers. Both the TLV for HAL and the SI, with the TWA or typical techniques, appear useful for epidemiological studies and surveillance. However, the utility of TWA, typical, and peak techniques for job design and intervention is dubious.

Risk assessments using the Strain Index and the TLV for HAL, Part I: Task and multi-task job exposure classifications.

BACKGROUND: The Strain Index (SI) and the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value for Hand Activity Level (TLV for HAL) use different constituent variables to quantify task physical exposures. Similarly, time-weighted-average (TWA), Peak, and Typical exposure techniques to quantify physical exposure from multi-task jobs make different assumptions about each task's contribution to the whole job exposure. Thus, task and job physical exposure classifications differ depending upon which model and technique are used for quantification. This study examines exposure classification agreement, disagreement, correlation, and magnitude of classification differences between these models and techniques. METHODS: Data from 710 multi-task job workers performing 3,647 tasks were analyzed using the SI and TLV for HAL models, as well as with the TWA, Typical and Peak job exposure techniques. Physical exposures were classified as low, medium, and high using each model's recommended, or a priori limits. Exposure classification agreement and disagreement between models (SI, TLV for HAL) and between job exposure techniques (TWA, Typical, Peak) were described and analyzed. RESULTS: Regardless of technique, the SI classified more tasks as high exposure than the TLV for HAL, and the TLV for HAL classified more tasks as low exposure. The models agreed on 48.5% of task classifications (kappa = 0.28) with 15.5% of disagreement between low and high exposure categories. Between-technique (i.e., TWA, Typical, Peak) agreement ranged from 61-93% (kappa: 0.16-0.92) depending on whether the SI or TLV for HAL was used. CONCLUSIONS: There was disagreement between the SI and TLV for HAL and between the TWA, Typical and Peak techniques. Disagreement creates uncertainty for job design, job analysis, risk assessments, and developing interventions. Task exposure classifications from the SI and TLV for HAL might complement each other. However, TWA, Typical, and Peak job exposure techniques all have limitations. Part II of this article examines whether the observed differences between these models and techniques produce different exposure-response relationships for predicting prevalence of carpal tunnel syndrome.

Work-related illness and injury claims among nationally certified athletic trainers reported to Washington and California from 2001 to 2011.

BACKGROUND: Little is known about the work-related injury and illnesses experienced by certified athletic trainers (AT). METHODS: The incidence and characteristics of injury/illness claims filed in two workers' compensation systems were described from 2001 to 2011. Yearly populations at risk were estimated from National Athletic Trainers' Association membership statistics. Incidence rate ratios (IRR) were reported by job setting. RESULTS: Claims were predominantly for traumatic injuries and disorders (82.7%: 45.7% sprains/strains, 12.0% open wounds, 6.5% bruises) and at these body sites (back 17.2%, fingers 12.3%, and knee 9.6%) and over half were caused by body motion and overexertion (51.5%). Compared with school settings, clinic/hospital settings had modestly higher claim rates (IRR = 1.29, 95% CI: 1.06-1.52) while other settings (e.g., professional or youth sport, nursing home) had lower claim rates (IRR = 0.63, 95% CI: 0.44-0.70). CONCLUSIONS: These first known estimates of work-related injuries/illnesses among a growing healthcare profession help identify occupational tasks and settings imposing injury risk for ATs. Am. J. Ind. Med. 59:1156-1168, 2016. © 2016 Wiley Periodicals, Inc.

Impact of Work Organizational Factors on Carpal Tunnel Syndrome and Epicondylitis.

OBJECTIVE: The aim of this study was to identify relationships between work organizational variables (job rotation, overtime work, having a second job, and work pacing) (These work organizational variables and their relationships with biomechanical and psychosocial exposures were studied previously and published in a separate paper.) and health outcome measures [carpal tunnel syndrome (CTS), lateral and medial epicondylitis (LEPI/MEPI)]. METHODS: Using a pooled baseline cohort of 1834 subjects, the relationships were studied using logistic regression models. RESULTS: Varied degrees of associations between the work organizational and outcomes variables were found. Job rotation was significantly associated with being a CTS case [odds ratio (OR) = 1.23, 95% confidence interval (95% CI): 1.00 to 1.50]. Overtime work was significantly associated with lower LEPI prevalence (OR = 0.48, 95% CI: 0.28 to 0.84). No statistically significant associations were found between having a second job and different work pacing and any of the three health outcome measures. CONCLUSIONS: Work organizational variables were only partially associated with the studied health outcomes.

Relationships between job organisational factors, biomechanical and psychosocial exposures.

The relationships between work organisational, biomechanical and psychosocial factors were studied using cross-sectional data from a pooled dataset of 1834 participants. The work organisational factors included: job rotation, overtime work, having second jobs and work pace. Task and job level biomechanical variables were obtained through sub-task data collected in the field or analysed in the laboratory. Psychosocial variables were collected based on responses to 10 questions. The results showed that job rotations had significant effects on all biomechanical and most psychosocial measures. Those with job rotations generally had higher job biomechanical stressors, and lower job satisfaction. Overtime work was associated with higher job biomechanical stressors, and possibly self-reported physical exhaustion. Those having second jobs reported getting along with co-workers well. Work pace had significant influences on all biomechanical stressors, but its impact on job biomechanical stressors and psychosocial effects are complicated. PRACTITIONER SUMMARY: The findings are based on a large number of subjects collected by three research teams in diverse US workplaces. Job rotation practices used in many workplaces may not be effective in reducing job biomechanical stressors for work-related musculoskeletal disorders. Overtime work is also associated with higher biomechanical stressors.

Contrasting patterns of care for musculoskeletal disorders and injuries of the upper extremity and knee through workers' compensation and private health care insurance among union carpenters in Washington State, 1989 to 2008.

BACKGROUND: Musculoskeletal symptoms and disorders (MSDIs) are common reasons for visits to medical providers in the general population and they are common work-related complaints. Prior reports raise concerns as to whether declines in workers' compensation (WC) rates represent true improvement in occupational health and safety or shifting of care to other payment systems. METHODS: By linking administrative records, we compared patterns of WC claims and private health care utilization for disorders of the upper extremity (UE) and knee among a large cohort of union carpenters over a 20-year period. RESULTS: As WC claim rates declined, private health care utilization increased. The increase was muted somewhat but sustained when adjusting for other patterns of health care utilization. CONCLUSIONS: Findings suggest the decline of WC claim rates do not solely represent improved occupational safety in this population, but also a considerable shifting of care to their private insurance coverage over time.

Workers' compensation claims for musculoskeletal disorders and injuries of the upper extremity and knee among union carpenters in Washington State, 1989-2008.

BACKGROUND: Numerous aspects of construction place workers at risk of musculoskeletal disorders and injuries (MSDIs). Work organization and the nature of MSDIs create surveillance challenges. METHODS: By linking union records with workers' compensation claims, we examined 20-year patterns of MSDIs involving the upper extremity (UE) and the knee among a large carpenter cohort. RESULTS: MSDIs were common and accounted for a disproportionate share of paid lost work time (PLT) claims; UE MSDIs were three times more common than those of the knee. Rates declined markedly over time and were most pronounced for MSDIs of the knee with PLT. Patterns of risk varied by extremity, as well as by age, gender, union tenure, and predominant work. Carpenters in drywall installation accounted for the greatest public health burden. CONCLUSIONS: A combination of factors likely account for the patterns observed over time and across worker characteristics. Drywall installers are an intervention priority.

Developing a pooled job physical exposure data set from multiple independent studies: an example of a consortium study of carpal tunnel syndrome.

BACKGROUND: Six research groups independently conducted prospective studies of carpal tunnel syndrome (CTS) incidence in 54 US workplaces in 10 US States. Physical exposure variables were collected by all research groups at the individual worker level. Data from these research groups were pooled to increase the exposure spectrum and statistical power. OBJECTIVE: This paper provides a detailed description of the characteristics of the pooled physical exposure variables and the source data information from the individual research studies. METHODS: Physical exposure data were inspected and prepared by each of the individual research studies according to detailed instructions provided by an exposure subcommittee of the research consortium. Descriptive analyses were performed on the pooled physical exposure data set. Correlation analyses were performed among exposure variables estimating similar exposure aspects. RESULTS: At baseline, there were a total of 3010 participants in the pooled physical exposure data set. Overall, the pooled data meaningfully increased the spectra of most exposure variables. The increased spectra were due to the wider range in exposure data of different jobs provided by the research studies. The correlations between variables estimating similar exposure aspects showed different patterns among data provided by the research studies. CONCLUSIONS: The increased spectra of the physical exposure variables among the data pooled likely improved the possibility of detecting potential associations between these physical exposure variables and CTS incidence. It is also recognised that methods need to be developed for general use by all researchers for standardisation of physical exposure variable definition, data collection, processing and reduction.

Exposure-response relationships for the ACGIH threshold limit value for hand-activity level: results from a pooled data study of carpal tunnel syndrome.

OBJECTIVES: This paper aimed to quantify exposure-response relationships between the American Conference of Governmental Industrial Hygienists' (ACGIH) threshold limit value (TLV) for hand-activity level (HAL) and incidence of carpal tunnel syndrome (CTS). METHODS: Manufacturing and service workers previously studied by six research institutions had their data combined and re-analyzed. CTS cases were defined by symptoms and abnormal nerve conduction. Hazard ratios (HR) were calculated using proportional hazards regression after adjusting for age, gender, body mass index, and CTS predisposing conditions. RESULTS: The longitudinal study comprised 2751 incident-eligible workers, followed prospectively for up to 6.4 years and contributing 6243 person-years of data. Associations were found between CTS and TLV for HAL both as a continuous variable [HR 1.32 per unit, 95% confidence interval (95% CI) 1.11-1.57] and when categorized using the ACGIH action limit (AL) and TLV. Those between the AL and TLV and above the TLV had HR of 1.7 (95% CI 1.2-2.5) and 1.5 (95% CI 1.0-2.1), respectively. As independent variables (in the same adjusted model) the HR for peak force (PF) and HAL were 1.14 per unit (95% CI 1.05-1.25), and 1.04 per unit (95% CI 0.93-1.15), respectively. CONCLUSION: Those with exposures above the AL were at increased risk of CTS, but there was no further increase in risk for workers above the TLV. This suggests that the current AL may not be sufficiently protective of workers. Combinations of PF and HAL are useful for predicting risk of CTS.

Predicting work-related incidence of lateral and medial epicondylitis using the strain index.

BACKGROUND: The Strain Index (SI) has been developed to evaluate the risk for developing a distal upper extremity disorder. The objective of this study is to determine if the SI predicts incidence cases of work-related lateral, medial, or any epicondylities (LEPI, MEPI, and EPI). METHODS: Six hundred seven workers were followed for up to 3.5 years, 70 developed EPI on the dominant side (44 LEPI, 13 MEPI, and 13 both). Survival analyses were conducted adjusting for demographic, psychosocial, and work organizational factors, with the SI as time-dependent variable. RESULTS: High exposure (SI > 5), older age, and self-perceived poor general health were associated with incidence of LEPI and EPI, but not MEPI. There was a significant relationship between higher scores of SI and LEPI, hazard ratio (HR) 2.00 (95% CI 1.04-3.87) for SI 5.1-12, HR 2.12 (95% CI 1.11-4.05) for SI > 12. CONCLUSIONS: The SI can effectively identify jobs with increased risk of developing incidence of LEPI.

Twenty years of workers' compensation costs due to falls from height among union carpenters, Washington state.

BACKGROUND: Falls from height (FFH) are a longstanding, serious problem in construction. METHODS: We report workers' compensation (WC) payments associated with FFH among a cohort (n = 24,830; 1989-2008) of carpenters. Mean/median payments, cost rates, and adjusted rate ratios based on hours worked were calculated using negative-binomial regression. RESULTS: Over the 20-year period FFH accounted for $66.6 million in WC payments or $700 per year for each full-time equivalent (2,000 hr of work). FFH were responsible for 5.5% of injuries but 15.1% of costs. Cost declines were observed, but not monotonically. Reductions were more pronounced for indemnity than medical care. Mean costs were 2.3 times greater among carpenters over 50 than those under 30; cost rates were only modestly higher. CONCLUSIONS: Significant progress has been made in reducing WC payments associated with FFH in this cohort particularly through 1996; primary gains reflect reduction in frequency of falls. FFH that occur remain costly.

The association between combination of hand force and forearm posture and incidence of lateral epicondylitis in a working population.

OBJECTIVE: The objective of this prospective study is to investigate the exposure-response relationships between various workplace physical exposures of force, repetition, and their combination assessed at an individual level with lateral epicondylitis (LE). BACKGROUND: Workplace upper extremity musculoskeletal disorders (UEMSDs) are prevalent, disabling, and expensive. LE is one of the major UEMSDs in active workers. METHOD: We used detailed health history, symptoms, and physical examination for identifying incidence and detailed exposure assessment to capture work tasks of each worker and to measure quantitative mechanical workload. We used counting process style input of proportional hazards regression for modeling cumulative incidence that accounts for changed exposure estimates during the follow-up period when respondents change jobs. RESULTS: The incidence rate of LE on the dominant side was 4.91 per 100 person-years. Adjusted for age and gender, the combined effect of forearm pronation > or = 45 degrees for > or = 40% of time and time spent with forceful exertion, including any power grip (hazard ratio [HR] = 2.8, 95% confidence interval [CI] = [1.35-5.77]), lifting for > or = 3% of time (HR = 2.50, 95% CI = [1.19-5.24]), and duty cycle for forceful exertion for > or = 10% (HR = 2.25, 95% CI = [1.09-4.66]), were significant predictors of dominant side LE, whereas neither the awkward posture nor the forceful exertion alone was significant. Older workers with jobs requiring a high percentage of time working with force in combination with awkward postures of forearm were more likely to predict LE. CONCLUSION: This study shows the evidence of the etiologic role of strenuous manual tasks in the occurrence of LE.

How well are we controlling falls from height in construction? Experiences of union carpenters in Washington State, 1989-2008.

BACKGROUND: Falls from height (FFH) continue to cause significant morbidity and mortality across the construction industry. METHODS: By linking data on work hours with workers' compensation records, rates of work-related injuries resulting from FFH and associated days away from work were evaluated among a large cohort (n = 24,830) of union carpenters in Washington State from 1989 to 2008. Using Poisson regression we assessed rates of FFH over the 20-year period while adjusting for temporal trend in other work-related injuries. Patterns of paid lost days (PLDs) were assessed with negative binomial regression. RESULTS: Crude rates of FFH decreased 82% over the 20-year period. Reductions were more modest and without demonstrable change since 1996 when adjusting for the temporal reduction in other injuries. Younger workers had higher injury rates; older workers lost more days following falls. Rates of PLDs associated with falls decreased over time, but there was not a consistent decline in mean lost days per fall. CONCLUSION: These patterns are consistent with decreased FFH for several years surrounding state (1991) and then federal (1994) fall standards; the decline during this time period exceeded those seen in injury rates overall in this cohort. While crude rates of FFH have continued to decline, the decline is not as substantial as that seen for other types of injuries. This could reflect a variety of things including more global efforts designed to control risk (site planning, safety accountability) and changes in reporting practices.

Pooling job physical exposure data from multiple independent studies in a consortium study of carpal tunnel syndrome.

Pooling data from different epidemiological studies of musculoskeletal disorders (MSDs) is necessary to improve statistical power and to more precisely quantify exposure-response relationships for MSDs. The pooling process is difficult and time-consuming, and small methodological differences could lead to different exposure-response relationships. A sub-committee of a six-study research consortium studying carpal tunnel syndrome: (i) visited each study site, (ii) documented methods used to collect physical exposure data and (iii) determined compatibility of exposure variables across studies. Certain measures of force, frequency of exertion and duty cycle were collected by all studies and were largely compatible. A portion of studies had detailed data to investigate simultaneous combinations of force, frequency and duration of exertions. Limited compatibility was found for hand/wrist posture. Only two studies could calculate compatible Strain Index scores, but Threshold Limit Value for Hand Activity Level could be determined for all studies. Challenges of pooling data, resources required and recommendations for future researchers are discussed. PRACTITIONER SUMMARY: There is a need for standardised measures and measurement protocols of physical exposure for the upper extremity. This study may provide guidance for those planning to conduct an epidemiological study on quantified job physical exposures, or planning to merge physical exposure data from similar studies with some methodologic differences.

Who pays for work-related traumatic injuries? Payer distribution in washington state by ethnicity, injury severity, and year (1998-2008).

BACKGROUND: Acute work-related trauma is a leading cause of death and disability for U.S. workers but it is difficult to obtain information about injured workers not covered by workers' compensation (WC). This study aimed to: (1) describe trends in expected payer and linkage to WC claims, (2) compare characteristics of injured workers who did and did not have a linked WC claim, and (3) describe variation in expected payer and linkage to WC claims by ethnicity and injury severity. METHODS: Data for injuries occurring from 1998 through 2008 were obtained from the Washington State Trauma Registry and linked to WC claims. RESULTS: We found that 27% of work-related traumatic injuries did not have WC listed as a payer, while 37% did not link to a WC claim. Among those with WC listed as a payer, the odds of having a linked WC claim were 57% lower for workers with other non-WC insurance compared with the otherwise uninsured. Latinos were more likely to have a linked WC claim compared with non-Latinos, but there was no significant difference after partially controlling for WC-covered employment and other insurance. CONCLUSIONS: This study demonstrated the importance of considering differential access to other insurance coverage and adaptation by health care settings to financial pressures when assessing trends in occupational injury incidence and reporting, especially when using WC as a proxy for work-relatedness. The addition of occupation, industry, and work status to trauma registries and hospital discharge databases would improve surveillance, research, policy and prevention efforts.

Effects of residential location and work-commuting on long-term work disability.

PURPOSE: Little is known about the independent effect of workers' residential location and work-commuting on their long-term disability due to work-related injuries. We examined 149,110 incident claims while adjusting for multiple risk factors in a large, population-based sample of Washington State workers' compensation State Fund claims during 2002-2008. METHODS: Claimants' residential addresses were geocoded with census tract and aggregated into four category classification of the Rural Urban Commuting Area Codes (RUCAs) which takes into account for tract-level work-commuting. We used logistic regressions to assess the association between RUCAs and whether or not a person was off work for more than 180 days due to injury; Quantile regressions to predict various percentiles of cumulative lost workdays by RUCAs. RESULTS: Compared to those who live in the Urban Core, workers in other areas experienced longer average paid time loss days due to work-related injury. The association between residential location and long-term disability was significant, odds ratio (OR) 1.19 (95 % confidence interval (CI) 1.11-1.27) for residents of Small Town and Isolated Rural and OR 1.17 (95 % CI 1.12-1.22) for those of Sub Urban, and persisted after controlling for injury nature, socio-demographic, employment-related, and claim administrative characteristics. The impact of residential location and work-commuting elevated as the duration of disability increased. CONCLUSIONS: This study shows that residential location and work-commuting has a significant and time-varying impact on duration of work disability. Workers living in Sub Urban and Small Town and Isolated Rural areas represent a particularly vulnerable group with respect to risk of long-term work disability.

Predicting work-related disability and medical cost outcomes: estimating injury severity scores from workers' compensation data.

PURPOSE: Acute work-related trauma is a leading cause of death and disability among US workers. The research objectives were to assess: (1) the feasibility of estimating Abbreviated Injury Scale-based injury severity scores (ISS) from ICD-9-CM codes available in workers' compensation (WC) medical billing data, (2) whether ISS predicts work-related disability and medical cost outcomes, (3) whether ISS adds value over other injury severity proxies, and (4) whether the utility of ISS differs for an all-injury sample compared with three specific injury samples (amputations, extremity fractures, traumatic brain injury). METHODS: ISS was estimated from ICD-9-CM codes using Stata's user-written -icdpic- program for 208,522 compensable nonfatal WC claims for workers injured in Washington State from 1998 to 2008. The Akaike Information Criterion and R(2) were used to compare severity measures. Competing risks survival analysis was used to evaluate work disability outcomes. Adjusted total medical costs were modeled using linear regression. RESULTS: Work disability and medical costs increased monotonically with injury severity. For a subset of 4,301 claims linked to the Washington State Trauma Registry (WTR), there was moderate agreement between WC-based ISS and WTR-based ISS. Including ISS together with an early hospitalization indicator resulted in the most informative models; however, early hospitalization is a more downstream measure. CONCLUSIONS: ISS was significantly associated with work disability and medical cost outcomes for work-related injuries. Injury severity should be considered as a potential confounder for occupational injury intervention, program evaluation, or outcome studies, and can be estimated using existing software when ICD-9-CM codes are available.

Twenty years of work-related injury and illness among union carpenters in Washington State.

BACKGROUND: Individuals who work in the construction industry are at high risk of occupational injury. Robust surveillance systems are needed to monitor the experiences of these workers over time. METHODS: We updated important surveillance data for a unique occupational cohort of union construction workers to provide information on long-term trends in their reported work-related injuries and conditions. Combining administrative data sources, we identified a dynamic cohort of union carpenters who worked in Washington State from 1989 through 2008, their hours worked by month, and their workers' compensation claims. Incidence rates of reported work-related injuries and illnesses were examined. Poisson regression was used to assess risk by categories of age, gender, time in the union, and calendar time contrasting medical only and paid lost time claims. RESULTS: Over the 20-year study period, 24,830 carpenters worked 192.4 million work hours. Work-related injuries resulting in medical care or paid lost time (PLT) from work occurred at a rate of 24.3 per 200,000 hr worked (95% CI: 23.5-25.0). Medical only claims declined 62% and PLT claims declined 77%; more substantive declines were seen for injuries resulting from being struck and falls to a lower level than from overexertion with lifting. Differences in risk based on union tenure and age diminished over time as well. CONCLUSIONS: Significant declines in rates of reported work-related injuries and illnesses were observed over the 20-year period among these union carpenters. Greater declines were observed among workers with less union tenure and for claims resulting in PLT.

Trends in the disproportionate burden of work-related traumatic injuries sustained by Latinos.

OBJECTIVE: Disproportionate occupational injury rates for Latinos are well documented, but there is limited information about whether disparity is increasing over time. This study describes trends in the burden of work-related traumatic injuries sustained by Latinos in Washington State. METHODS: Washington State Trauma Registry data from 1998 to 2008 were used to model annual change in the odds that a work-related traumatic injury was sustained by a Latino, controlling for demographics, injury-related factors, and Latino representation in the underlying labor force. RESULTS: We found a 5% mean annual increase in the odds that a comparable work-related traumatic injury was sustained by a Latino (P = 0.007). Falls in industrial/mine/quarry locations were the strongest contributor to increasing disparity. CONCLUSIONS: Latinos bear an increasingly disproportionate burden of occupational injuries and are less likely to have health insurance coverage aside from workers' compensation.