The relationship between shift work, circadian rhythms, and cognitive function in ICU nursing

Nurses work 24-hour shifts due to the critical importance of patient care. The human body has a circadian rhythm that regulates many physiological activities. Shift work is associated with decreased melatonin levels and disruption of the circadian rhythm. Given the vital role of cognitive functions such as working memory and attention, this study investigated the impact of circadian rhythm disturbances on the cognitive performance of intensive care unit (ICU) nurses in Qazvin City, Iran.

The study population consisted of 36 nurses. The assessment tools included a demographic questionnaire, a circadian rhythm questionnaire, and cognitive function tests (attention and working memory) using the Stroop Test and Wechsler Adult Intelligence Scale, administered at the beginning and end of each of the three shifts. The data was analyzed using descriptive statistics, including mean, standard deviation, and frequency percentages. The Kolmogorov-Smirnov test was used to determine the normality of the data. The data analysis involved analytical statistics using mixed-effects models performed using R software version 4. The significance level was at p < 0.05 for the present study.

The nurses exhibited a high degree of circadian rhythm inflexibility, with 83.3% classified as " inflexibile" and 91.7% as " vigorous ".|The nurses' cognitive performance was highest during the morning shift, with better attention and working memory abilities. A one-unit increase in the stability and amplitude of the circadian rhythm was associated with reductions in memory span, congruent response time, and incongruent response time during the evening and night shifts.

Given the observed decline in specific cognitive functions during evening and night shifts, the likelihood of increased errors during these shifts is heightened. The cumulative effect of circadian rhythm disruptions can manifest as diminished cognitive performance. The rhythm stability and amplitude could serve as predictive indicators for staffing shift work systems to prevent errors and enhance the system's efficiency.