Job strain and risk of musculoskeletal symptoms among a prospective cohort of occupational computer users.

OBJECTIVES: Most previous studies of the association between psychosocial stress and musculoskeletal illness among computer users have been cross-sectional and have yielded inconsistent results. The association between a measure of psychosocial stress, "job strain", and incident neck-shoulder and arm-hand musculoskeletal symptoms was investigated among recently hired computer users.

METHODS: The participants worked for one of several large employers and were followed prospectively for 6 months. The "job demands" and "decision latitude" subscales of the Job Content Questionnaire were used to estimate the job-strain quadrants and a ratio measure of job strain which was subsequently categorized. Incident musculoskeletal symptoms were obtained with weekly diaries. Proportional hazards models were used to estimate associations between job strain and incident musculoskeletal symptoms.

RESULTS: Those in the high-strain quadrant were at increased risk of neck-shoulder symptoms [hazard ratio (HR) 1.65, 95% confidence interval (95% CI) 0.91-2.99] when compared with those in the low-strain quadrant. Those in the highest strain-ratio category were also at increased risk of neck-shoulder symptoms when compared with those in the lowest strain-ratio category (HR 1.52, 95% CI 0.88-2.62). Modification by previous years of computer use was observed, with an elevated risk observed for those in the highest job-strain ratio category who also had low previous computer use (HR 3.16, 95% CI 1.25-8.00). There did not appear to be an association between either measure of job strain and incident arm-hand symptoms.

CONCLUSIONS: In this cohort, workers who reported high job strain were more likely to develop neck-shoulder symptoms.