To determine the relationship between stress Factors and work-related musculoskeletal symptoms of assembly line workers in the automobile industry.

A cross-sectional study was conducted in two Factories of automobile manufacturing companies where inappropriate posture and repetitive motions were required. The total number of subjects was 636, and consisted entirely of men. The Age, length of work duration, marital status, education level, smoking status, drinking status, sleeping time and stress scores were investigated according to subgroups of general characteristics. We divided the subjects into a Reference group and a Stress risk group to compare the frequency of the variables between them. The stress scores of the Positive symptom group were compared with the Symptom free group by the t-test. To measure the stress level, the PWI(Psychosocial Well being Index) which consists of 4 Factors, totaling 45 items, was used. A standardized self-reported questionnaire was used to assess the symptoms in workers. The criteria for positive symptoms were based on Operational Definition of Work-related Musculoskeletal Disorders of the NIOSH.

1) The subgroups of Age, Work duration, Marital status, Education level, Smoking status, Drinking status and Sleeping time revealed no differences in frequencies in musculoskeletal symptoms. 2) Higher PWI(p<0.05), Factor 3(p<0.05) and Factor 4(p<0.01) scores were observed in younger workers compared with older workers. 3) The workers who had work durations between 11-15 years showed higher PWI(p<0.01), Factor 2(p<0.01), Factor 3(p<0.01), and Factor 4(p<0.01), compared with other work duration subgroups. 4) Singles had higher Factor 4 scores(p<0.01). 5) The sleeping time of less than 6 hours a day expressed a higher PWI(p<0.01), Factor 2(p<0.05), and Factor 3(p<0.01), Factor 4(p<0.05). 6) There was no difference in the prevalence of musculoskeletal symptoms between the Reference group and Stress risk group. 7) The subjects who had Positive musculoskeletal symptoms showed a significant difference in Factor 2 scores compared with the Symptom free groups. 8) According to a univariate logistic regression analysis, Factor 2(OR: 1.02, 95% CI: 1.00-1.04, p-value: 0.0291) expressed significant but mild effects on the musculoskeletal symptoms and a multivariate logistic regression showed a statistically significant effect on musculoskeletal symptoms(OR:1.04, 95% CI: 1.01-1.07, p-value: 0.0170).

Psychosocial stress scores were not higher in symptomatic subjects compared with those who had no symptoms. Sleeping longer showed a protective effect on symptoms but this was not statistically significant. There was no relationship between the stress scores and musculoskeletal symptoms in social performance and self-confidence, general well-being and vitality. Factor 2(Depression) was statistically significant though its effect was mild. Limited to this study, We could find partial relationship between psychosocial stress(Depression) and musculoskeletal symptoms. So it could therefore be suspected that ergonomic or other unknown factors may be more significant causes of musculoskeletal symptoms but we did not investigate these.