Effects of a Snack on Performance and Errors During a Simulated 16-h Night Shift: a Pilot Study

Abstract

\n Background: Night shift workers might not eat due to their busy schedules during the night shift. However, diet may not only satisfy hunger, but also affect performance and errors.The aim of this study was to clarify the effect of a snack on performance and errors during 2-day, 16-h simulated night shifts. Methods: A randomized repeated-measure crossover study was performed to investigate subjective and cognitive performance in 15 healthy female adults (mean age, 21.7 years) after they consumed a snack (352 kcal) during a simulated night shift (16:00 to 09:00). The participants were kept awake from wake up in the morning to the next day at 09:00. Subjects were tested for performance on the Uchida-Kraepelin test, as well as for subjective feeling, body temperature, psychomotor vigilance test, and heart rate variability, before and after they consumed the snack. One day before the experiment, all participants wore an actigraphy monitoring device to determine their sleep state. Results: There was no difference between the snack condition and the skipping condition in sleep states the day before the experiment. On the day of the experiment, between 16:00 and 09:00, subjective sleepiness, fatigue, and body temperature were not different between the two conditions. Subjects showed a significant improvement in performance on the Uchida-Kraepelin test and total errors on the psychomotor vigilance test, the primary outcome measure, when they consumed a snack compared with the skipping condition. In addition, the snack condition was associated with decreased high-frequency power, decreased low-frequency power/high-frequency power ratio, and increased heart rate, in the vagally mediated heart rate variability indices, which may reflect a higher ability to modulate cognitive and behavioral processes. Conclusions: These results suggest that providing a snack to shift workers during night shifts might improve work safety and efficiency.Trial registration: This study was registered with the University Hospital Medical Information Network-Clinical Trials Registry (UMIN-CRT registry ID: UMIN 000034345).