A new study suggests ideal napping strategies when staying up late, looking at whether no naps, one long nap, or two short naps are better at eliminating sleepiness and fatigue so you can stay as productive as possible. If you are a medical worker working shifts, a student about to take an exam, or a new parent with a baby who does not understand the circadian cycle, then "staying up all night" is not an unfamiliar concept.

Sanae Oriyama, a researcher at Hiroshima University in Japan, used data from previous studies to examine the impact of the length and timing of naps on sleepiness, fatigue and work performance among nursing staff during the night shift. They say their findings apply to first-time parents as well.

Oriyama said: "A 90-minute nap can maintain long-term work performance, and a 30-minute nap can maintain low fatigue and quick reactions. As a strategic combination of naps, it is valuable for early morning work efficiency and safety."

During the day, our light-sensitive internal (circadian) clock activates wake-up functions, and at night, it is ready to shut down. Night shifts can disrupt these circadian rhythms, causing sleepiness, poor concentration, and reduced productivity. Some studies show that napping can lessen the negative effects of a night shift.

Nursing staff in Japan's public hospitals can typically sleep or rest for up to two hours during a 16-hour night shift. During a simulated 4:00 pm to 9:00 am shift, Oriyama compared taking a 120-minute nap (one-nap group), a 90-minute nap followed by a 30-minute nap (two-nap group), or no nap during a simulated night shift to see the effects of each on alertness and cognitive performance.

Oriyama found that taking no naps or taking only one nap was associated with increased sleepiness and subjective fatigue between 4:00 and 9:00 a.m. compared with the two-nap group. She found that segmented naps that ended at 3 a.m. helped reduce the effects of sleepiness and fatigue.

When it comes to cognitive performance, one or two naps won't improve your productivity. However, during the 90-minute nap, the nurses who took longer to fall asleep performed worse on the Uchida-Kleepelin Test (UKT), a timed basic mathematics test designed to measure speed and accuracy in performing tasks.

"For example, during a night shift that lasts from 4 p.m. to 9 a.m., when tasks requiring rapid reactions to maintain a high level of safety are scheduled between 2 a.m. and 9 a.m., 90-minute and 30-minute segmented naps ending at 12 a.m. and 3 a.m., respectively, are considered more effective than a 120-minute monophasic nap ending at 12 a.m."

Studies have also found that the timing of naps is also important. Research results show that starting a nap later should be avoided, but it is a delicate balance: the later the nap is, the more effective it is in resisting sleepiness; however, if the nap is extended too long, it will affect concentration at work as the desire for sleep increases.

The researchers say 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 minimizing sleep-deprived fatigue in mothers raising infants," Oriyama said.

There are limitations to this study. First, the research was conducted under laboratory conditions, which are different from actual working conditions. Second, the women recruited into the study had no experience of shift work, which may have affected the findings. Therefore, the ideal nap time and ideal nap schedule during long-term night shifts need further elucidation.

The research was published in the journal Scientific Reports.