Post-shift recovery sleep duration and its association with daytime sleepiness among night-shift nurses: a repeated-measures observational study.

Objective: To examine the association between post-shift recovery sleep duration and daytime sleepiness among night-shift nurses. Methods: A repeated-measures observational study among night-shift nurses in a tertiary hospital. Data were collected between September and November 2025. Post-shift recovery sleep duration, defined as sleep obtained within 24 h after completing a night shift, was categorized as 0 h, <2 h, 2-4 h, or ≥4 h. Daytime sleepiness was assessed using the Epworth Sleepiness Scale (ESS). Linear mixed-effects models with random intercepts were applied to evaluate associations while controlling for sex, working unit, night-shift workload, caffeine intake during night shifts, and insomnia severity. Results: Recovery sleep duration was associated with daytime sleepiness across sleep-duration categories. Nurses reporting 2-4 h of recovery sleep had the highest ESS scores compared with those reporting no recovery sleep (ES, ±95% Conclusions: Post-shift recovery sleep duration was associated with daytime sleepiness among night-shift nurses, with intermediate recovery sleep duration (2-4 h) showing the highest ESS scores. Because recovery sleep duration was self-reported and the study design limits causal inference, these findings should be interpreted as associations rather than evidence of causality. Fatigue risk management strategies should consider not only sleep duration but also the quality and context of post-shift recovery.