Abstract
Background: shift work is associated with both sleepiness and reduced performance. The aim of this study was to examine cognitive performance, sleepiness, and sleep quality among petrochemical control room shift workers. Method: Sixty shift workers participated in this study. Cognitive performance was evaluated using the objective test such as continuous performance test, n-back test, and simple reaction time test; sleepiness scale was measured using the subjective Karolinska Sleepiness Scale (KSS); and sleep quality was assessed using Pittsburgh Sleep Quality Index (PSQI) questionnaire. ANCOVA, t-test, and repeated-measures ANOVA was used for statistical analyses, and the significance level was set at p < .05. Results: All variables related to cognitive performance, except for omission error, significantly decreased at the end of both day and night shifts (p < .0001). There were also significant differences between the day and night shifts in terms of the variables of omission error (p < .027) and commission error (p < .036). A significant difference was also observed between daily and nightly trends of sleepiness (p < .0001) so that sleepiness was higher for the night shift. Participants had low sleep quality on both day and night shifts, and there were significant differences between the day and night shifts in terms of subjective sleep quality and quantity (p < .01). Conclusion: Long working hours per shift result in fatigue, irregularities in the circadian rhythm and the cycle of sleep, induced cognitive performance decline at the end of both day and night shifts and increased sleepiness in night shift. It, thus, seems necessary to take ergonomic measures such as planning for more appropriate shift work and reducing working hours.