Effects of shift work on cortisol levels among nurses: a systematic review

Shift work is essential in nursing to ensure continuous patient care; however, it is associated with adverse health outcomes. Cortisol, a key stress hormone regulated by the circadian rhythm, is often disrupted by shift work. This systematic review aimed to examine the association between types of shift work and cortisol levels in nurses. The systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, and the study protocol was registered in PROSPERO (CRD42025641432). A comprehensive literature search was performed using seven databases (PubMed, EMBASE, CINAHL, Cochrane library, Web of Science, PsycINFO, and Scopus) to identify studies published after 2000 that investigated the relation between shift work and cortisol levels among nurses on 4 November 2024. The risk of bias was assessed using ROBINS-I, and results were synthesized narratively because of heterogeneity in study designs and cortisol measurement methods. Eight studies met our inclusion criteria. Comparisons between nurses working fixed daytime shifts and those on night shifts consistently showed elevated cortisol levels and circadian rhythm disruption in night-shift nurses. However, findings on rotating shift schedules (including two-shift vs. three-shift rotations and rotating vs. fixed shifts) were inconsistent. The overall risk of bias was high, primarily owing to confounding factors and participant selection. In conclusion, shift work, particularly fixed night shifts, was linked to cortisol imbalance and circadian misalignment among nurses. Future research should incorporate confounding variables into analytical models to enhance the accuracy of findings. Additionally, optimized shift schedules should be developed and implemented to promote individual wellbeing and workforce sustainability.