Background Work-related musculoskeletal disorders (WMSDs) are one of the major occupational health problems faced by bus drivers and should receive special attention.

Objective To explore the associations of weekly working hours and sleep quality with neck and lower back WMSDs among bus drivers, as well as assess the potential mediating role of sleep quality.

Methods From June to December 2022, we recruited bus drivers from 5 subsidiaries of the Shenzhen Bus Group by convenient sampling method. Demographic characteristics, lifestyles, and work-related features of the bus drivers were collected through a questionnaire survey. The Pittsburgh Sleep Quality Index (PSQI) scale and the Musculoskeletal Disorders Survey Questionnaire were used to assess sleep quality and WMSDs respectively. Logistic regression models were applied to analyze the associations of weekly working hours and sleep quality with WMSDs in neck and lower back. Furthermore, mediation analysis was performed to investigate the role of sleep quality in the associations between weekly work hours and neck and lower back WMSDs.

Results A total of 1792 valid questionnaires were collected, with a response rate of 95.07%. Among these, 89.3% of the bus drivers worked more than 40 h per week, and the positive rate of poor sleep quality was 28.2%. The overall positive rate of WMSDs within one year before the survey was 69.12%. Among different body regions, the leading positive rates were identified in neck and lower back regions, at 55.92% and 53.68%, respectively. The logistic regression model showed that compared to the bus drivers with weekly work hours ≤40 h, those weekly worked (40~48 h (OR=1.43, 95%CI: 1.02, 2.01; OR=1.65, 95%CI: 1.17, 2.34), (48~56 h (OR=2.69, 95%CI: 1.89, 3.83; OR=2.30, 95%CI: 1.62, 3.29) and ＞56 h (OR=2.63, 95%CI: 1.86, 3.74; OR=3.23, 95%CI: 2.27, 4.62) had significantly increased risk of WMSDs in neck and lower back. Additionally, when compared to those with good sleep quality, bus drivers with poor sleep quality had higher risks of both neck and lower back WMSDs (OR=4.08, 95%CI: 3.20, 5.23; OR=4.15, 95%CI: 3.26, 5.30, respectively). Further mediation analysis indicated that sleep quality partially mediated the associations between weekly working hours and both neck and lower back WMSDs, with 36.15% and 33.68% as the respective proportion of mediation.

Conclusion The positive rate of WMSDs is high among bus drivers, and the most common WMSDs occur in neck and lower back. Long working hours and poor sleep quality are significantly associated with increased risks of neck and lower back WMSDs. Sleep quality may mediate the associations of weekly working hours with neck and lower back WMSDs.