Associations of rotating shift work with depressive symptoms among Chinese nurses: exploratory indirect associations through sleep problems

Rotating shift work has been associated with depressive symptoms, but its association with depressive symptom severity and the statistical intermediary pattern involving sleep quality remain incompletely understood. We conducted a cross-sectional analysis of baseline data (2021–2024) from the Chinese Nurses’ Health Cohort Study (TARGET), including 43,697 registered nurses from 105 hospitals across 15 provinces in China. Primary analyses compared rotating shifts with fixed day shifts, while fixed night shifts were included in sensitivity analyses. Depressive symptoms and sleep quality were assessed using the 9-item Patient Health Questionnaire (PHQ-9) and Pittsburgh Sleep Quality Index (PSQI). Multivariable ordinal and binary logistic regression models were used to estimate associations. Exploratory model-based indirect associations were estimated using probit models with bootstrap resampling. Among the participants, 93.8% were women and 64.4% worked rotating shifts. Compared with fixed day shifts, rotating shifts were consistently associated with higher odds of depressive symptoms across four cumulative PHQ-9 contrasts (OR range, 1.471–1.500; all P < 0.001) and with poor sleep quality (OR, 1.592; 95% CI, 1.514–1.674; P < 0.001). Poor sleep quality statistically accounted for 38.6% (95% CI, 34.2%–43.2%) of the observed association between rotating shifts and depressive symptoms under the fitted model. All seven PSQI components showed statistically supported indirect associations. Sleep latency had the numerically largest estimated percentage statistically accounted for (39.3%; 95% CI, 24.2%–45.0%). In the reverse-pathway specification, depressive symptoms statistically accounted for 14.8% (95% CI, 13.7%–16.0%) of the observed association between rotating shifts and poor sleep quality. Rotating shifts were consistently associated with greater depressive symptom severity and poor sleep quality. The observed statistical intermediary patterns highlight sleep quality, particularly sleep latency, as an important priority for assessment and for prospective evaluation of sleep-focused strategies among nurses working rotating shifts. Although causal direction cannot be established from these cross-sectional data, the findings provide a focused basis for future longitudinal and interventional research. TARGET, ChiCTR2100043202 and ChiCTR2300072756. Initial registration completed on 8 February, 2021.