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and that can also produce exposure data at the level of detail needed to examine etiologic relationships
with musculoskeletal disease. The HAL, as developed by Latko, is easy to apply and has proven to be
predictive of the prevalence of upper extremity musculoskeletal disorders in cross-sectional studies.
2.1.4.2 Psychosocial Exposures
Measures of psychosocial exposures reported in the literature are obtained through the use of various
self-report surveys. These surveys are typically presented to subjects in a paper format in which the
subject is requested to complete a series of questions. These survey tools typically comprise multiple
scales used to assess psychosocial risk factors. Many of these measures assess the construct of interest
using a continuous scale of measurement, by which it is possible to provide a measure of exposure in
terms of degree, and not simply whether it was present or absent. Response items vary depending on
the scale and typically range from 0 to 5, 0 to 7, or 0 to 10, with options anchored so that the respondent
has a frame of reference for various responses.
Some measures are standardized, well-developed, self-report tools whose psychometric properties
(reliability and validity) have been established based on past research, while other items or scales were
developed for the purposes of single study. Currently, all scales used are self-report. Depending on the
length of the survey, the time for completion can range from 10 min to several hours. It is rare that the
perceptions reported by the respondent are corroborated by an independent assessment tool or process
(e.g., supervisor or coworker evaluations or direct observation of a workplace). Although it can be
helpful to assess such independently collected information to support workers' reports of their sense or
opinions of their environments, perceptions are, by their nature, best collected through self-report.
The most common work-related psychosocial constructs measured in the epidemiologic literature
include: job satisfaction, mentally demanding work, monotony, relationships at work that include co-
worker and supervisor support, daily problems at work, job pressure, hours under deadline per week,
limited control over work, job insecurity, and psychological workload (a composite of a number of sub-
items that include stress at work, workload, extent of feeling tired, feeling exhausted after work, rest break
opportunities, and mental strain),
The job content questionnaire (JCQ) is an example of a workplace psychosocial measure whose
measurement properties are well defined; it has been used frequently in the psychosocial epidemiology
literature. The JCQ comprises three key measures of job characteristics: mental workload (psychological
job demands), decision latitude, and social support (Karasek, 1985). Decision latitude is based on the
worker's decision authority and the worker's discretion over skill use — that is, the worker's ability to
control the work process and to decide which skills to utilize to accomplish the job. Psychological job
demands reflect both physical pace of work and time pressure in processing or responding to infor-
mation. In the Karasek and Theorell model (1990), high psychological job demands in combination
with low decision latitude result in residual job strain and, over time, chronic adverse health effects.
The JCQ, as an instrument for measuring such strain, has been shown to be highly reliable and has
been validated as a predictor, in numerous countries and industrial sectors, of increased risk of cardio-
vascular morbidity (Karasek and Theorell, 1990; Karasek et al., 1998; Kawakami et al., 1995; Kawakami
and Fujigaki, 1996; Kristensen, 1996; Schwartz et al., 1996; Theorell, 1996).
2.1.5 Measures of Musculoskeletal Disorder Outcomes
The epidemiologic literature on the relationship between exposure to physical and psychosocial risk
factors and the development of musculoskeletal disorders in the workplace focuses on four major
types of outcomes. Two outcomes rely on patient self-report (symptoms and work status), and two
rely on sources independent of the patient (evaluation by a clinician and review of workplace or insur-
ance records). Table 2.1 summarizes the outcomes assessed in 132 epidemiologic studies. These do not
include the 29 upper extremity studies that provided indirect measures of exposure.
Self-report symptommeasures were the most common outcomes, with 61 studies assessing presence of
symptoms (usually nonstandardized questionnaires asking about prevalence or incidence), 19 studies
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