A new study has proposed the ideal snoozing strategy when you’re staying up all night, examining whether taking no naps, one long nap or two shorter ones is better at combatting drowsiness and fatigue and maintaining work performance.
If you’re a healthcare worker who does shift work, a student with upcoming exams, or a new parent with a baby who doesn’t understand day-night cycles, then “pulling an all-nighter” is not a foreign concept. Using data from previous studies, Sanae Oriyama, a researcher from Hiroshima University, Japan, investigated how the length and timing of naps taken by nursing staff during a night shift affected drowsiness, fatigue, and work performance. They say their findings could apply to new parents, too.
“A 90-minute nap to maintain long-term performance and a 30-minute nap to maintain lower fatigue levels and fast reactions, as a strategic combination of naps, can be valuable for early morning work efficiency and safety,” said Oriyama.
During daylight hours, our light-sensitive internal (circadian) body clock activates wakefulness, while at night, it readies itself to switch off. Night shift messes with these circadian rhythms, leading to drowsiness, decreased concentration, and reduced efficiency. Some studies have shown that napping may reduce the negative effects of night shift.
Nursing staff at Japanese public hospitals are usually allowed to sleep or rest for up to two hours during a 16-hour night shift. During a simulated 4:00 p.m. to 9:00 a.m. shift, Oriyama compared having a single 120-minute nap (one-nap group) during a simulated night shift, having a 90-minute nap followed by a 30-minute one (two-nap group) or having no nap to see how each affected alertness and cognitive performance.
Oriyama found that taking no naps or one nap was associated with worse drowsiness from 4:00 a.m. to 9:00 a.m. and increased subjective fatigue compared to the two-nap group. On the other hand, having two naps reduced drowsiness until 6:00 a.m. and fatigue until 9:00 a.m. She found that a split nap ending at 3:00 a.m. helped mitigate the effects of drowsiness and fatigue.
In terms of cognition, neither one nor two naps resulted in improved performance. However, nurses who took longer to fall asleep during the 90-minute nap session showed poorer scores in the Uchida-Kraepelin test (UKT), a timed basic math exam meant to measure speed and accuracy in performing a task.
“During a night shift that, for example, lasts from 4:00 p.m. to 9:00 a.m. the next morning, a split nap of 90 minutes and 30 minutes, ending at 12:00 a.m. and 3:00 a.m., respectively, is thought to be more effective than a 120-minute monophasic nap ending at 12 am when tasks requiring quick responses to maintain a high level of safety are scheduled between 2:00 am and 9:00 am,” Oriyama said.
The study also found that the timing of naps is important. Oriyama says the findings suggest that starting naps later should be avoided, but it’s a delicate balance: the later you nap, the more effective it is in fending off sleepiness; however, delaying it for too long can interfere with work focus as the desire to sleep increases.
The researcher says the study’s findings could be useful to new parents.
“The results of this study can be applied not only to night shift workers but also to minimize sleep deprivation fatigue in mothers raising infants,” Oriyama said.
Oriyama notes the limitations of the study. Firstly, it was conducted under laboratory conditions, which vary from actual work conditions. Secondly, the women recruited for the study had no shift work experience, which may have affected the results.
“Hence, the ideal time for taking a nap and the ideal nap schedule during long night shifts need further elucidation,” she said.
The study was published in the journal Scientific Reports.
Source: Hiroshima University
