China's automobile manufacture is a labor-intensive industry, and most of the welding tasks are manual operations. It is often necessary to observe the solder joints during operation, and there are many adverse health outcome-related factors involved in the work process. However, the research on the prevalence and risk factors of work-related musculoskeletal disorders (WMSDs) in the upper back of welders is still insufficient.

To explore the prevalence and risk factors of WMSDs in the upper back of welders from an automobile factory.

This was a cross-sectional study. A cluster random sampling method was used to select 972 electric welders from an automobile factory as the study subjects. The Musculoskeletal Disorders Questionnaire was used to estimate the prevalence of WMSDs in the upper back in the past year.

The prevalence rate of WMSDs in the upper back in the welders was 42.2% (410/972). The positive rates of studied occupational risk factors were 72.5% (705/972) for maintaining same posture for a long time, 71.8% (698/972) for bending and twisting for a long time, and 64.7% (629/972) for repetitive trunk movements. The univariate analysis showed that the prevalence rates of WMSDs were significantly different among workers categorized by gender, working age, twisting and/or bending for a long time, working in the same position for a long time, lifting heavy objects in an uncomfortable position, repetitive trunk movements, being unable to exert energy due to discomfort, work involving cold or temperature changes, personnel shortage, no rest between work, working hours per week, and working in an uncomfortable position (P<0.05). The results of multiple logistic regression indicated that female, working in the same position for a long time, working in an uncomfortable position (frequently), lifting heavy objects in an uncomfortable position, and being unable to exert energy due to discomfort were associated with higher risks of reporting WMSDs in the upper back (OR=2.37, 1.46, 1.76, 1.44, and 1.50, respectively, P<0.05); the risk of reporting WMSDs in the upper back increased by 95%, 157%, and 196% for every 10 h increase in weekly working hours (41-50 h, 51-60 h, ≥61 h vs ≤40 h); adequate rest time was associated with a lower risk for WMSDs in the upper back (OR=0.70, 95%CI: 0.49-0.98).

The prevalence rate of WMSDs in the upper back of welders in the automobile factory is high, and many occupational risk factors are involved. Measures should be taken for intervention and prevention.