Ann Marie Dale

Prevalence and incidence of carpal tunnel syndrome in US working populations: pooled analysis of six prospective studies

OBJECTIVES Most studies of carpal tunnel syndrome (CTS) incidence and prevalence among workers have been limited by small sample sizes or restricted to a small subset of jobs. We established a common CTS case definition and then pooled CTS prevalence and incidence data across six prospective studies of musculoskeletal outcomes to measure CTS frequency and allow better studies of etiology. METHODS Six research groups collected prospective data at > 50 workplaces including symptoms characteristic of CTS and electrodiagnostic studies (EDS) of the median and ulnar nerves across the dominant wrist. While study designs and the timing of data collection varied across groups, we were able to create a common CTS case definition incorporating both symptoms and EDS results from data that were collected in all studies. RESULTS At the time of enrollment, 7.8% of 4321 subjects met our case definition and were considered prevalent cases of CTS. During 8833 person-years of follow-up, an additional 204 subjects met the CTS case definition for an overall incidence rate of 2.3 CTS cases per 100 person-years. CONCLUSIONS Both prevalent and incident CTS were common in data pooled across multiple studies and sites. The large number of incident cases in this prospective study provides adequate power for future exposure-response analyses to identify work- and non-work-related risk factors for CTS. The prospective nature allows determination of the temporal relations necessary for causal inference.

Risk Factors for Carpal Tunnel Syndrome and Median Neuropathy in a Working Population

Objective:To assess whether work-related physical activities are associated with Carpal tunnel syndrome (CTS), even when controlling for personal risk factors. Methods:A cross-sectional assessment of 1108 workers from eight employers and three unions completed nerve conduction testing, physical examination, and questionnaires. CTS was defined by median neuropathy and associated symptoms. Results:Eighteen workers had CTS and 131 had evidence of median neuropathy. CTS was highest among construction workers (3.0%) compared to other subjects (<1%). Logistic regression models for median neuropathy both personal and work-related risk factors. Work-related exposures were estimated by two methods: self-report and job title based ratings. Conclusions:Both work and personal factors mediated median nerve impairment. Construction workers are at an increased risk of CTS so awareness should be raised and interventions should specifically target this risk group.

Biomechanical risk factors for carpal tunnel syndrome: a pooled study of 2474 workers.

Background Between 2001 and 2010, five research groups conducted coordinated prospective studies of carpal tunnel syndrome (CTS) incidence among US workers from various industries and collected detailed subject-level exposure information with follow-up of symptoms, electrophysiological measures and job changes. Objective This analysis examined the associations between workplace biomechanical factors and incidence of dominant-hand CTS, adjusting for personal risk factors. Methods 2474 participants, without CTS or possible polyneuropathy at enrolment, were followed up to 6.5 years (5102 person-years). Individual workplace exposure measures of the dominant hand were collected for each task and included force, repetition, duty cycle and posture. Task exposures were combined across the workweek using time-weighted averaging to estimate job-level exposures. CTS case-criteria were based on symptoms and results of electrophysiological testing. HRs were estimated using Cox proportional hazard models. Results After adjustment for covariates, analyst (HR=2.17; 95% CI 1.38 to 3.43) and worker (HR=2.08; 95% CI 1.31 to 3.39) estimated peak hand force, forceful repetition rate (HR=1.84; 95% CI 1.19 to 2.86) and per cent time spent (eg, duty cycle) in forceful hand exertions (HR=2.05; 95% CI 1.34 to 3.15) were associated with increased risk of incident CTS. Associations were not observed between total hand repetition rate, per cent duration of all hand exertions, or wrist posture and incident CTS. Conclusions In this prospective multicentre study of production and service workers, measures of exposure to forceful hand exertion were associated with incident CTS after controlling for important covariates. These findings may influence the design of workplace safety programmes for preventing work-related CTS.

Personal and workplace psychosocial risk factors for carpal tunnel syndrome: a pooled study cohort.

Background Between 2001 and 2010, six research groups conducted coordinated multiyear, prospective studies of carpal tunnel syndrome (CTS) incidence in US workers from various industries and collected detailed subject-level exposure information with follow-up symptom, physical examination, electrophysiological measures and job changes. Objective This analysis of the pooled cohort examined the incidence of dominant-hand CTS in relation to demographic characteristics and estimated associations with occupational psychosocial factors and years worked, adjusting for confounding by personal risk factors. Methods 3515 participants, without baseline CTS, were followed-up to 7 years. Case criteria included symptoms and an electrodiagnostic study consistent with CTS. Adjusted HRs were estimated in Cox proportional hazard models. Workplace biomechanical factors were collected but not evaluated in this analysis. Results Women were at elevated risk for CTS (HR=1.30; 95% CI 0.98 to 1.72), and the incidence of CTS increased linearly with both age and body mass index (BMI) over most of the observed range. High job strain increased risk (HR=1.86; 95% CI 1.11 to 3.14), and social support was protective (HR=0.54; 95% CI 0.31 to 0.95). There was an inverse relationship with years worked among recent hires with the highest incidence in the first 3.5 years of work (HR=3.08; 95% CI 1.55 to 6.12). Conclusions Personal factors associated with an increased risk of developing CTS were BMI, age and being a woman. Workplace risk factors were high job strain, while social support was protective. The inverse relationship between CTS incidence and years worked among recent hires suggests the presence of a healthy worker survivor effect in the cohort.

Is Disability Underreported Following Work Injury

Existing national data may underreport the full burden of occupational injuries and illnesses. This study sought to provide more complete reporting and to assess disability that persisted following return to work. Workers (n = 205) with a musculoskeletal injury resulting in 5 or more days of lost time or restricted duty were recruited from three employers. Data on work status and functional limitations were derived from multiple sources including administrative records, medical records, and patient interviews at baseline and 6 months. Results indicate that many workers reported continuing difficulties functioning at work following return to full duty. Measures of health-related quality of life improved over 6 months, but bodily pain and physical functioning scores remained lower than expected based on national averages. Sixteen percent of workers were reinjured within a year following initial injury. Following return to work, many workers experienced reinjury or reported persistent limitations in function 6 months following injury. Based on study findings the conclusion is drawn that OSHA logs may provide accurate measures of initial episodes of time loss from work but may underrepresent the full magnitude of lost time following work injury.

Self-reported physical exposure association with medial and lateral epicondylitis incidence in a large longitudinal study

Introduction Although previous studies have related occupational exposure and epicondylitis, the evidence is moderate and mostly based on cross-sectional studies. Suspected physical exposures were tested over a 3-year period in a large longitudinal cohort study of workers in the USA. Method In a population-based study including a variety of industries, 1107 newly employed workers were examined; only workers without elbow symptoms at baseline were included. Baseline questionnaires collected information on personal characteristics and self-reported physical work exposures and psychosocial measures for the current or most recent job at 6 months. Epicondylitis (lateral and medial) was the main outcome, assessed at 36 months based on symptoms and physical examination (palpation or provocation test). Logistic models included the most relevant associated variables. Results Of 699 workers tested after 36 months who did not have elbow symptoms at baseline, 48 suffered from medial or lateral epicondylitis (6.9%), with 34 cases of lateral epicondylitis (4.9%), 30 cases of medial epicondylitis (4.3%) and 16 workers who had both. After adjusting for age, lack of social support and obesity, consistent associations were observed between self-reported wrist bending/twisting and forearm twisting/rotating/screwing motion and future cases of medial or lateral epicondylitis (ORs 2.8 (1.2 to 6.2) and 3.6 (1.2 to 11.0) in men and women, respectively). Conclusions Self-reported physical exposures that implicate repetitive and extensive/prolonged wrist bend/twisting and forearm movements were associated with incident cases of lateral and medial epicondylitis in a large longitudinal study, although other studies are needed to better specify the exposures involved.

Predictors of upper extremity symptoms and functional impairment among workers employed for 6 months in a new job

BACKGROUND We sought to identify personal and work-related predictors of upper extremity symptoms and related functional impairment among 1,108 workers employed for 6 months in a new job. METHODS We collected data at baseline and 6-month follow-up using self-administered questionnaires. Multivariate logistic regression models were created for each outcome variable. Predictors included personal risk factors, physical work exposures and psychosocial factors. RESULTS Independent predictors for upper extremity symptoms at 6-month follow-up were age, Caucasian race, female gender, baseline history of UE symptoms, and job tasks involving wrist bending or forceful gripping. Independent predictors for functional impairment were baseline history and severity of UE symptoms, wrist bending, and social support. CONCLUSIONS Both personal and work-related factors were independent predictors of upper extremity symptoms and functional impairment in this working population. We found different risk factors for symptoms than for functional impairment related to symptoms.

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.

Reliability of hand diagrams for the epidemiologic case definition of carpal tunnel syndrome

The purpose of this study was to evaluate the inter-rater reliability of hand diagrams, which are commonly used in research case definitions of carpal tunnel syndrome (CTS). To evaluate the potential of non-random misclassification of cases, we also studied predictors of rater disagreement as a function of personal and work factors, and of hand symptoms not classic for CTS. Participants in a longitudinal study investigating the development of CTS completed repeated self-administered questionnaires. Three experienced clinicians, blind to subjects’ work or personal history, independently rated all hand diagrams on an ordinal scale from 0 to 3. Disagreements between ratings were resolved by consensus. Reliability was measured by the weighted kappa statistic. Logistic regression models evaluated predictors of disagreement. Three hundred and thirty-three subjects completed 494 hand diagrams. Eighty-five percent were completed by self-administered questionnaire and 15% by telephone interview. Weighted kappa values representing agreement among the three raters, were 0.83 (95% CI: 0.78, 0.87) for right hand diagrams and 0.88 (95% CI: 0.83, 0.91) for left hand diagrams. Ratings from hand diagrams obtained by telephone interview produced better agreement. Agreement among raters was not affected by subjects’ personal or work factors. Disagreement among raters was associated with the presence of hand/wrist symptoms other than classic CTS symptoms. Overall, high levels of agreement were attained by independent raters of hand diagrams. Personal factors did not affect agreement among raters, but presence of non-CTS symptoms seemed to affect results and should be considered in studies focused on diverse populations with heterogeneity of upper extremity symptoms.

Associations between workplace factors and carpal tunnel syndrome: A multi-site cross sectional study.

BACKGROUND Few large epidemiologic studies have used rigorous case criteria, individual-level exposure measurements, and appropriate control for confounders to examine associations between workplace psychosocial and biomechanical factors and carpal tunnel syndrome (CTS). METHODS Pooling data from five independent research studies, we assessed associations between prevalent CTS and personal, work psychosocial, and biomechanical factors while adjusting for confounders using multivariable logistic regression. RESULTS Prevalent CTS was associated with personal factors of older age, obesity, female sex, medical conditions, previous distal upper extremity disorders, workplace measures of peak forceful hand activity, a composite measure of force and repetition (ACGIH Threshold Limit Value for Hand Activity Level), and hand vibration. CONCLUSIONS In this cross-sectional analysis of production and service workers, CTS prevalence was associated with workplace and biomechanical factors. The findings were similar to those from a prospective analysis of the same cohort with differences that may be due to recall bias and other factors.