Naps are brief sleep periods that take place outside a primary nocturnal period that are differentiated from unintentional and uncontrollable sleep bouts. Unintentional sleep could underlie a neurological condition, a sleep disorder, jetlag, or significantly inadequate nocturnal sleep.
Voluntary naps, on the other hand, function as a planned midday recharge that can enhance productivity and learning. The benefits of napping are well known, but the pressure to optimize workday time presents limitations for some of us on the practicality of regular napping.
Is there a recommended mid-afternoon nap duration that achieves a balance between significant benefits and practicability? A study answers that question.
After their normal amount of nocturnal sleep, 32 young adult individuals underwent 4 conditions of sleep tests on separate days: awake, a nap of 10 minutes, a nap of 30 minutes, and a nap of 60 minutes.
Sleep time measured objectively was compared with polysomnography instead of just the amount of nap time provisioned. This allowed for unambiguous decision-making regarding how long an individual should set aside for a nap, considering the average time taken falling asleep.
Cognitive performance, subjective sleepiness, and mood were measured at 5-minute intervals, 30-minute intervals, 60-minute intervals, and 240-minute intervals after waking up from the mid-afternoon naps to compare how long the respective nap benefits lasted. The effect on memory encoding of these nap durations was also looked at.
It took 10 to 15 minutes for the individuals to fall asleep on average. In comparison to being awake, all nap times ranging from 10 to 60 minutes had evident benefits for alertness, subjective sleepiness, and positive mood that lasted as much as 240 minutes after napping, indicating that even a short nap of 10 minutes can serve as a midday recharge.
Still, of the nap durations, only the 30-minute nap was beneficial for memory encoding, suggesting that 30 minutes might be the necessary minimum for memory benefits.
Vigilance improvements were moderate, and speed of processing benefits wasn’t observed. Sleep inertia, the grogginess right after waking that can manifest as temporary performance decrements, was seen only for the 30 to 60 minute naps. Nevertheless, decrements were insignificant and were resolved within 30 minutes of awakening.
Although no clear ‘winning’ nap duration was identified, a nap of 30 minutes seems to have the best trade-off between benefit and practicability. 30 minutes could be the recommended duration for a mid-afternoon nap while providing an additional ~10 minutes for falling asleep.
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