ABSTRACT
This study was performed to understand the incidence density and detect the risk factors of occupational low back pain. A cross-sectional study was conducted with a questionnaire in a welding material manufacturing factory in October, 1993. Therefore, we selected 140 workers who had never complained of low back pain as cohorts. Also, we added 236 newly entered persons who had never complained of low back pain. The total number of cohorts were 376 workers. And then we continued with a questionnaire survey in October, 1996 and with a questionnaire survey and medical examinations by a specialist in October, 1997. Follow-ups were done for 337 workers. The number of newly developed low back pain among workers were 127. The characteristics of low back pain were as follows. The durations of pain were less than or equal to 2 days (42.6%), from 3 days to less than 1 week (8.7%), from 1 week to less than 1 month (11.0%), 1 month or more (6.2%). The frequency was everyday (7.9%), once per week (21.3%), once per month (14.2%), once per 2-3 months (9.4%), once per 5 months (11.0%). The severity of pain was slight (9.4%), mild (33.1%), moderate (13.4%), severe (10.2%) and very severe (1.6%). The onset of most low back pain was insidious (41.7%). The diagnosis of low back pain was muscle strain (37.8%), lumbar sprain (23.6%) and myofacial pain syndrome (3.9%). The number of newly developed low back pain among workers were 127, their incidence density was 15.7 per 100 person-years. In univariate analysis, age, marital status, educational level, smoking habit, category of job, tenures and frequency of stretching exercises showed a statistical significance. The multivariate logistic regression analysis confirmed that category of job and tenures (p<0.05) were independent risk factors for low back pain among workers. The number of newly developed occupational low back pain among production workers were 71, their incidence density was 11.3 per 100 person-years. In univariate analysis, age, marital status, educational level, regular exercise, tenures, posture of waist and lifting of heavy materials showed a statistical significance. The multivariate logistic regression analysis confirmed that posture of waist (p<0.05) and lifting of heavy materials (p<0.1) were independent risk factors for occupational low back pain among production workers.