Weekly work hours and cervical spine dysfunction among video display terminal workers: mediating roles of...

Cervical spine dysfunction is common among video display terminal (VDT) workers. Although long work hours have been linked to musculoskeletal problems, how extended work hours relate to cervical spine dysfunction via psychosocial and behavioral factors remains insufficiently characterized. We examined the association between weekly work hours and cervical spine dysfunction and explored the potential mediating roles of occupational stress and sleep quality.

A cross-sectional study was conducted among 929 VDT workers from 10 companies in Shenzhen, China. Cervical spine dysfunction was assessed using the Neck Disability Index and dichotomized as dysfunction (NDI > 4) versus no dysfunction (NDI ≤ 4). Weekly work hours were categorized as ≤40, 41-48, 49-56, and ≥57 h/week. Occupational stress was measured using the Job Content Questionnaire (JCQ-22) and defined as a demand-control ratio >1. Sleep quality was assessed using the Pittsburgh Sleep Quality Index and categorized as poor (PSQI >5) versus good (PSQI ≤5). Multivariable logistic regression models adjusted for prespecified confounders were used. Mediation analyses were conducted using single- and parallel-mediator models; 5,000 bootstrap resamples were used for single-mediator models.

Longer weekly working hours were associated with higher odds of cervical spine dysfunction (adjusted ORs 2.10-2.70 vs. ≤ 40 h/week; all p ≤ 0.005). Occupational stress was associated with higher odds of cervical spine dysfunction (OR 1.62, 95% CI 1.29-2.03, p < 0.001), whereas good sleep quality was associated with lower odds (OR 0.25, 95% CI 0.19-0.32, p < 0.001). Weekly working hours were also associated with increased occupational stress (all p ≤ 0.002) and poorer sleep quality in some categories. In single-mediator models, the indirect effect via occupational stress was significant (p = 0.003), whereas the indirect effect via sleep quality was marginal (p = 0.068). In the parallel mediation model, indirect effects via occupational stress (IE 0.04, 95% CI 0.01-0.06, p = 0.009) and sleep quality (IE 0.06, 95% CI 0.01-0.11, p = 0.019) were significant, and the direct effect was not statistically significant (DE 0.05, 95% CI -0.05 to 0.15, p = 0.356).

Longer weekly work hours were associated with higher odds of cervical spine dysfunction among VDT workers. This association may be partly explained through indirect pathways involving occupational stress and sleep quality, supporting prevention strategies integrating working-time management with ergonomic/posture interventions, stress reduction, and sleep health promotion.