Background Work-related musculoskeletal disorders (WMSDs) seriously affect the health of workers. Many domestic studies focus on individual characteristics of employees, but as a workrelated disease, WMSDs are possibly clustered in some specific institutions.
Objective This study aims to analyze the morbidity of WMSDs at individual and institutional levels, and provide reference to prevent and control WMSDs.
Methods By stratified cluster sampling method, 16 institutions including administrative management, education, machinery manufacture, electricity, chemical industry, business, and medical service were selected from the institutions that ordered occupational physical examination services in Hangzhou in 2014, and the employees were asked to complete Nordic musculoskeletal questionnaire. Those reporting ache, pain, or discomfort symptoms in neck, shoulders, upper back, elbows, low back, wrists/hands, hips/thighs, knees, ankles/feet that lasted for more than 24 h were defined as WMSDs cases. The morbidity rates of WMSDs among the employees with different sex, marital status, and work types were compared by chi-square test. The variational tendencies of WMSDs with age, working years, education, and income level were tested by Cochran-Armitage tendency test. A two-level logistic model of WMSDs with institutions as level 2 units and employees as level 1 units was established by software MLwiN 2.0.
Results The morbidity rate of WMSDs in 1 686 workers was 50.1% (95% CI:47.7%-52.5%), and the rates were significantly different among the institutions (χ2=68.85, P < 0.01). The risk of WMSDs was 2.35 times higher for males versus females (χ2=51.63, P < 0.01), 1.32 times higher for those with ≥ 20 working years versus those with < 20 working years (χ2=5.00, P=0.03), 1.38 times higher for the ≥ 1500 yuan per capita monthly income group versus the < 1 500 yuan monthly income group (χ2=7.69, P < 0.01), 0.68 times for the single employees versus married ones (χ2=7.21, P < 0.01), and 1.35 times higher for mental labors versus mixed mental and manual labors (χ2=4.49, P=0.03). The random effect of level 2 unit was significant in zero model (χ2=4.21, P=0.04), but the two-level logistic model including individual characteristics was not significant (χ2=2.29, P=0.13).
Conclusion The morbidity rate of WMSDs is high among the selected employees. According to the two-level logistic model, those who are male, married, with ≥ 20 working years, earning high income, mental labors are target population for WMSDs prevention and control. The findings indicate that the congregation of WMSDs at institutional level is resulted from the clustering of individual characteristics among institutions.
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