Abstract
BackgroundWhen conducting large scale epidemiologic studies, it is a challenge to obtain quantitative exposure estimates, which do not rely on self-report where estimates may be influenced by symptoms and knowledge of disease status. In this study we developed a job exposure matrix (JEM) for use in population studies of the work-relatedness of hip and knee osteoarthritis.MethodsBased on all 2227 occupational titles in the Danish version of the International Standard Classification of Occupations (D-ISCO 88), we constructed 121 job groups comprising occupational titles with expected homogeneous exposure patterns in addition to a minimally exposed job group, which was not included in the JEM. The job groups were allocated the mean value of five experts’ ratings of daily duration (hours/day) of standing/walking, kneeling/squatting, and whole-body vibration as well as total load lifted (kg/day), and frequency of lifting loads weighing ≥20 kg (times/day). Weighted kappa statistics were used to evaluate inter-rater agreement on rankings of the job groups for four of these exposures (whole-body vibration could not be evaluated due to few exposed job groups). Two external experts checked the face validity of the rankings of the mean values.ResultsA JEM was constructed and English ISCO codes were provided where possible. The experts’ ratings showed fair to moderate agreement with respect to rankings of the job groups (mean weighted kappa values between 0.36 and 0.49). The external experts agreed on 586 of the 605 rankings.ConclusionThe Lower Body JEM based on experts’ ratings was established. Experts agreed on rankings of the job groups, and rankings based on mean values were in accordance with the opinion of external experts.
Highlights
When conducting large scale epidemiologic studies, it is a challenge to obtain quantitative exposure estimates, which do not rely on self-report where estimates may be influenced by symptoms and knowledge of disease status
In this paper we present a new twodimensional job exposure matrix (JEM) with job groups based on all currently used occupational titles in the Danish version of the International Standard Classification of Occupations (D-ISCO 88) [31] on one axis and expert ratings of five specific mechanical exposures to the lower extremities on the other
This left 689 occupational titles – representing 168 D-ISCO 88 codes - that were divided into 121 job groups, each containing 1–34 different occupational titles
Summary
When conducting large scale epidemiologic studies, it is a challenge to obtain quantitative exposure estimates, which do not rely on self-report where estimates may be influenced by symptoms and knowledge of disease status. Self-reported exposures entail validity problems to the extent that individuals with symptoms – or knowledge of disease status even in the absence of symptoms – overestimate their exposures leading to inflated estimates of exposure-response relationships This source of bias is of major concern in crosssectional and case – control studies of symptomatic OA and may be a problem in prospective longitudinal studies because patients may have endured gradually increasing joint symptoms for several years before they are diagnosed with primary hip or knee OA. The evidence-base for a causal relationship between symptomatic primary hip and knee OA and occupational mechanical exposures would be enhanced by studies (preferably longitudinal) using quantitative measures of generic exposures that are assessed independently of the musculoskeletal symptom status of the participants
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