Questionnaire-based mechanical exposure indices for large population studies--reliability, internal consistency and predictive validity.

OBJECTIVES: 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.

Chronic pain and the sociodemographic environment: results from the Pain Clinic at Malmö General Hospital in Sweden.

OBJECTIVE: To study the occurrence of chronic pain in relation to different sociodemographic factors. DESIGN AND PATIENTS: The study cohort included all 1,360 new patients who, between July 1, 1988, and June 30, 1991, were referred to the multidisciplinary Pain Clinic at Malmö General Hospital, Malmö, Sweden, because of chronic, nonmalignant pain. The patients were characterized by age, sex, type of pain (nociceptive, neurogenic, psychogenic), place of residence, and ethnic background. SETTING: The referred sample was from the municipality of Malmö, a city with 240,000 inhabitants in an industrialized area served by one hospital. RESULTS: The age and sex standardized number of patients referred per 10,000 inhabitants and year varied among the different city areas from 0.35 to 1.63. High-rate areas had, in comparison to the city average, a higher migration rate, a higher proportion of single households with children, a higher percentage of people in need of social security benefits, a higher unemployment rate, and a greater percentage of people with foreign background. The age and sex distribution differed greatly among the three pain categories. Nociceptive pain was the most common category, with a striking overrepresentation of young women. CONCLUSION: Our results support the view that the occurrence of pain in an urban population is related to a number of sociodemographic factors. Further studies should be performed to evaluate how these factors influence incidence, medical-seeking behavior, clinical course, and rules for referral.