A recent study has revealed that a unique nap regimen, consisting of a 90-minute nap followed by a 30-minute nap, is more effective in combating drowsiness and fatigue among night-shift workers compared to a single uninterrupted 120-minute nap. This research, featured in the journal Scientific Reports, analyzed pilot studies conducted on night-shift napping between 2012 and 2018.
According to the study’s sole author, Sanae Oriyama, a nursing science professor at Hiroshima University’s Graduate School of Biomedical and Health Sciences, “A 90-minute nap for sustained long-term performance and a 30-minute nap to reduce fatigue and maintain quick reactions, when strategically combined, can significantly enhance work efficiency and safety during the early morning hours.”
120-minute nap concluding at midnight led to increased drowsiness
Oriyama revisited earlier pilot studies to assess alertness and performance after napping throughout a simulated overnight shift from 4 p.m. to 9 a.m. The research indicated that a single 120-minute nap concluding at midnight led to increased drowsiness, whereas two naps—a 90-minute nap ending at midnight followed by a 30-minute nap concluding at 3 a.m.—successfully prevented drowsiness.
Oriyama further explained, “Depending on the nature of the work and the time of day, I aim to explore the possibility of combining multiple naps and selecting those that prove most effective in reducing drowsiness, fatigue, and maintaining performance.”
She added, “For example, during an extended night shift from 4 p.m. to 9 a.m. the following morning, dividing the nap into 90 minutes and 30 minutes, concluding at 12 a.m. and 3 a.m. respectively, appears to be more advantageous than a continuous 120-minute nap ending at 12 a.m.”
Interestingly, individuals who took longer to fall asleep during the 90-minute nap phase exhibited lower scores on the Uchida-Kraepelin test (UKT), a timed math assessment designed to measure task speed and accuracys.
Oriyama suggested that these findings could have practical applications for new parents, stating, “The outcomes of this study can be applied not only to night-shift workers but also to help reduce sleep-deprivation fatigue among mothers caring for infants.”