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.
Department of Occupational and Environmental Medicine, Lund University, Lund University Hospital, Sweden. istvan.balogh@ymed.lu.se
I
I
Balogh
P
P
Orbaek
J
J
Winkel
C
C
Nordander
K
K
Ohlsson
J
J
Ektor-Andersen
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