[Association between neck ergonomic load, job fatigue and work-related musculoskeletal disorders]

Objective: To explore the relationship between neck ergonomic load, job fatigue and work-related musculoskeletal disorders (WMSDs), and to provide a scientific basis for formulating preventive measures for WMSDs in the neck. Methods: From January 2018 to December 2023, a stratified cluster sampling method was adopted to select front-line workers from over 400 enterprises of different scales in 22 provinces and cities across 7 geographical regions in China as the research subjects. The "Chinese version of Musculoskeletal Disorders Questionnaire" was used to conduct an epidemiological investigation on neck WMSDs nationwide, collecting information such as general characteristics, neck ergonomic load, neck fatigue, and the occurrence of WMSDs. A total of 83006 participants were included in the study. Multivariate logistic regression analysis was used to analyze the influencing factors of neck WMSDs occurrence, and the Bootstrap mediation analysis method was used to explore the mediating effect of fatigue between ergonomic load and neck WMSDs. Results: The incidence of neck fatigue among workers was 35.70% (29630 people), and the annual incidence of WMSDs was 22.32% (18530 people). The annual incidence of neck WMSDs among workers with neck fatigue was 45.79% (13568/29630), significantly higher than that of non-fatigued workers (9.30%, 4962/53376) (P<0.001). The results of multivariate logistic regression analysis showed that poor neck posture (slightly forward tilt, significant forward tilt, and backward tilt), maintaining the same posture for a long time, maintaining a head-down posture for a long time, maintaining a head-turning posture for a long time, and performing repetitive operations multiple times per minute significantly increased the risk of neck WMSDs (P<0.001) ; workers with job fatigue evaluated as "a little tiring" or above had a significantly increased risk of neck WMSDs (P<0.001). The results of mediating effect analysis showed that neck posture, maintaining the same posture for a long time, maintaining a head-down posture for a long time, maintaining a head-turning posture for a long time, and performing repetitive operations multiple times per minute all had direct effects on neck WMSDs, with effect values of 0.432, 0.574, 0.505, 0.231, and 0.424, respectively; neck fatigue played a partial mediating role between the above ergonomic load and neck WMSDs, and the indirect effect composition ratios were 22.02%, 29.40%, 26.92%, 23.26%, and 24.15%, respectively. Conclusion: The occurrence of neck WMSDs among workers is related to poor neck posture and repetitive operations; fatigue plays a mediating role in the relationship between poor neck ergonomic load (poor posture, repetitive operations) and neck WMSDs. Improving neck working posture and arranging proper breaks during work may be effective methods for preventing WMSDs by alleviating neck fatigue.