Questionnaire-based mechanical exposure indices for large population studies--reliability, internal consistency and predictive validity.
OBJECTIVE
This study attempts to construct valid indices for mechanical exposure of the shoulder-neck region with relation to the development of shoulder-neck pain in a 1-year perspective study of a general population.


METHODS
A comprehensive questionnaire was presented to 14 556 subjects aged 45 or 65 years and repeated after 12 months. Twenty-four questions concerning positions, movements, and manual materials handling were registered on a 3-point impact scale. Musculoskeletal problems were reported on a slightly modified version of the Standardized Nordic Questionnaire for the Analysis of Musculoskeletal Symptoms. Test-retest stability after 2 weeks was calculated for 232 consecutive participants. Based on mechanistic theories, 4 exposure indices were formed. Another 5 constructs were obtained by factor analysis.


RESULTS
All the indices showed good test-retest stability, and 5 of them had very good internal consistency. Due to overlaps between the indices, 2 indices stood out as having unique properties. One of them concerned mainly postures and the other dealt primarily with measured lifting. However, the latter was not related to the shoulder-neck pain outcome when adjusted for the posture index. The posture index showed an exposure-effect relationship with the outcome. The job titles implied a large degree of exposure misclassification.


CONCLUSIONS
The posture index is recommended as a mechanical exposure index for analyses of interaction with other possible determinants of shoulder-neck pain (ie, psychosocial factors). The use of such an index instead of job titles in large population studies will reduce the risk of misclassification.
Balogh
I
I
Department of Occupational and Environmental Medicine, Lund University, Lund University Hospital, Sweden. istvan.balogh@ymed.lu.se
Orbaek
P
P
Winkel
J
J
Nordander
C
C
Ohlsson
K
K
Ektor-Andersen
J
J
D000704:Analysis of Variance; D015331:Cohort Studies; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D019547:Neck Pain / Q000453:epidemiology*; D016273:Occupational Exposure / Q000009:adverse effects*; D010147:Pain Measurement; D010349:Patient Compliance; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D020069:Shoulder Pain / Q000453:epidemiology*; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology; D016526:Workload