Two Short Naps Beat One Long Nap, Says Study

Have you ever experienced that everything hurts after a sleepless night? A recent study has uncovered a neurotransmitter, N-arachidonoyl dopamine (NADA), linked to the pain caused by sleep deprivation, offering potential avenues for treatment. In sleep-deprived mouse models, researchers found reduced NADA levels in a brain region associated with sensory processing and arousal. Administering NADA to this area effectively alleviated the heightened pain response.

In a groundbreaking study, researchers concluded that two naps are more effective than a single long nap, with a 90-minute rest followed by a quick 30-minute nap.

Researchers at Hiroshima University conducted a study aimed at finding effective ways to stay awake and alert during these demanding shifts. Their findings suggest that taking later proving to be the winning strategy. This approach can be particularly beneficial for night shift workers and even new parents.


The study’s findings were published in the journal Scientific Reports, and according to its author, Professor Sanae Oriyama, a 90-minute nap contributes to long-term performance improvement, while a 30-minute nap helps maintain alertness and reduces tiredness for quicker reactions. Combining both nap lengths can enhance efficiency and safety during early morning work hours.


Working night shifts is a common practice in critical fields like healthcare, but it can have adverse effects on health and job performance. Our natural circadian rhythms make us naturally alert during the day and sleepy at night, which can lead to mistakes and accidents, especially in high-stress professions such as healthcare.

To combat this, workers often resort to napping. In Japan, nurses are permitted to nap for up to two hours during 16-hour night shifts. The study aimed to determine the most effective nap schedule to combat sleepiness and cognitive decline during these extended shifts and assess its impact on sleep quality.

Oriyama revisited earlier studies she had been involved in to analyze how naps affect alertness and performance during simulated overnight shifts from 4 p.m. to 9 a.m. Her research spanned three studies: one in 2012 with a single nap, one in 2014 with two naps, and one in 2018 with no nap.


The goal is to use these findings to tailor the appropriate nap strategies for different types of work and times of day to reduce drowsiness, fatigue, and maintain optimal performance.

The research showed that individuals who took a single 120-minute nap until midnight tended to feel more tired starting at 4 a.m. and remained fatigued until the end of their shift. In contrast, those who had two naps, one lasting 90 minutes until midnight and another for 30 minutes until 3 a.m., remained alert until 6 a.m.

Additionally, Oriyama suggested adding a 30-minute nap between 5-6 a.m. since tiredness tends to increase from 7-8 a.m. While all nap groups experienced increased tiredness from 4-9 a.m., the two-nap group reported experiencing it less intensely than the others.

Oriyama concluded, “During a night shift that, for example, lasts from 4 p.m. to 9 a.m. the next morning, a split nap of 90 minutes and 30 minutes, ending at 12 a.m. and 3 a.m., respectively, is thought to be more effective than a 120-minute monophasic nap ending at midnight when tasks requiring quick responses to maintain a high level of safety are scheduled between 2 a.m. and 9 a.m.”


Interestingly, both long and short naps didn’t significantly improve cognitive performance. However, if individuals took a longer time to fall asleep during the 90-minute nap, their performance on a math test suffered. It takes 90 minutes to complete a sleep cycle, and waking up before that can lead to grogginess. In contrast, previous studies have shown that naps of 30 minutes or less can boost alertness and energy.

The timing of the nap also appears to matter, with napping later being more effective for staying awake. However, waiting too long can impact focus as the body’s sleep drive accumulates. Further research is needed to determine the best timing and schedule for naps during long night shifts.

Oriyama believes that her findings can benefit night shift workers and new parents dealing with sleep deprivation caused by caring for infants.

The study involved 41 women in their 20s who participated in a 16-hour night shift simulation in a controlled environment. They underwent math tests, and various physiological factors, including temperature, drowsiness, fatigue, heart rate, and blood pressure, were closely monitored. Scheduled nap times were provided in a darkened room, and the quality of their sleep during these naps was assessed.


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