Is musculoskeletal pain a consequence or a cause of occupational stress? A longitudinal study.

OBJECTIVES Longitudinal studies have linked stress at work with a higher incidence of musculoskeletal pain. We aimed to explore the extent to which musculoskeletal pain is a cause as opposed to a consequence of perceived occupational stress. METHODS As part of the international cultural and psychosocial influences on disability study, we collected information from 305 Italian nurses, at baseline and again after 12 months, about pain during the past month in the low-back and neck/shoulder, and about effort-reward imbalance (ERI) (assessed by Siegrist's ERI questionnaire). Poisson regression was used to assess the RR of ERI >1 at follow-up according to the report of pain and of ERI >1 at baseline. RESULTS Among nurses with ERI ≤1 at baseline, ERI >1 at follow-up was associated with baseline report of pain in the low-back (RR 2.7, 95 % CI 1.4-5.0) and neck/shoulder (RR 2.6, 95 % CI 1.3-5.1). However, there was no corresponding association with persistence of ERI in nurses who already had ERI >1 at baseline. Associations of ERI at baseline with pain at follow-up were weak. CONCLUSION Our results suggest that the well-documented association between job stress and musculoskeletal pain is not explained entirely by an effect of stress on reporting of pain. It appears also that workers who report musculoskeletal pain are more likely to develop subsequent perceptions of stress. This may be because pain renders people less tolerant of the psychological demands of work. Another possibility is that reports of pain and stress are both manifestations of a general tendency to be aware of and complain about symptoms and difficulties.