BACKGROUND: Circadian rhythm sleep disorders (CRSDs) are common among healthcare workers (HCWs) and may impair alertness and cognitive performance during night shifts. This study examined CRSDs associations with cognitive function and sleepiness during overnight duty.
METHODS: Seventy-six hospital employees (80.3% female; mean age 31.8 ± 7.5 years) participated in this cross-sectional study. Based on clinical evaluation, participants were classified as normal circadian rhythm, delayed sleep phase syndrome (DSPS), and shift work sleep disorder (SWSD). Sleepiness was measured using Karolinska Sleepiness Scale (KSS) and Epworth Sleepiness Scale (ESS). Cognitive and psychomotor performance were assessed at the start and end of an 8-hour night shift using reaction time, minor lapses, memory span, and digit span tests. Statistical analyses included ANOVA, paired t-tests, Wilcoxon, and Kruskal-Wallis tests.
RESULTS: The prevalence of DSPS and SWSD was 13.2% and 15.7%. Total sleep duration did not differ significantly between CRSDs (P > 0.05). Reaction times and minor lapses increased significantly after the night shift (P < 0.05). Memory span, forward and reverse digit recall, and total correct responses all declined post-shift (P < 0.01). KSS scores increased significantly (P = 0.001). Reaction times and minor lapses differed significantly between CRSD subgroups, with SWSD participants demonstrating the greatest decline in performance.
CONCLUSIONS: HCWs with SWSD, exhibited greater cognitive deterioration and sleepiness during night shifts compared with normal circadian rhythms, whereas individuals with DSPS show relatively preserved performance. These findings highlight the importance of early recognition and occupational strategies to mitigate cognitive fatigue and associated risks in shift-working HCWs.
