Napping during the day has numerous health benefits — if it’s done correctly. The ideal nap time for most adults is 10 to 20 minutes. Naps shorter than 10 minutes provide minimal rejuvenation, while those exceeding the 20-minute mark often lead to sluggishness and sleep problems that night.
Napping and Circadian Rhythm
Our bodies follow a biological 24-hour clock known as ‘circadian rhythm,’ which regulates sleep according to the presence or absence of natural sunlight. We wake up and feel more alert in the morning when sunlight first appears. This energy sustains us until the sun goes down that night, at which point we begin to feel tired.
The circadian sleep cycle consists of two distinct phases: non-rapid eye movement (REM) sleep and REM sleep. Non-REM sleep begins as soon as we first fall asleep. The muscles relax, brain activity declines, and we experience decreases in heart rate and body temperature. The ‘slow-wave’ non-REM stage begins roughly 30 minutes after we fall asleep. Heart rate, blood pressure, and breathing rates fall to their lowest levels.
The REM phase begins as the slow-wave non-REM stage concludes. REM is linked to deep sleep, shallow breathing, and dreaming. Our bodies are essentially motionless except for our eyes, which dart back and forth (hence the name ‘rapid eye movement’). Most adults will cycle through the full non-REM and REM cycle every 90 to 120 minutes, and experience four to six cycles per eight hours of sleep.
The key to napping is to sleep long enough to experience the early stages of non-REM sleep, but to wake up before the slow-wave non-REM stage begins. Waking up in the early stages of non-REM makes us feel refreshed and more alert. Waking up during the slow-wave stage, on the other hand, can cause feelings of grogginess for long periods after the nap has ended. Naps that reach the slow-wave stage can also lead to prolonged sleep latency, or how long it takes to fall asleep, that night.
Why 10 to 20 Minutes?
A 2006 study published in SLEEP — the official journal of the Sleep Research Society (SRS) — noted that 10-minute naps led to ‘immediate improvements’ in cognitive performance. Sleepers felt less fatigued and had more stamina, and this energy sustained for roughly 155 minutes on average.
The same cognitive improvements were reported from those who napped for 20 minutes, although most improvements began roughly 35 minutes after the nap ended. These sleepers experienced improvements for roughly 125 minutes once they began.
The study also evaluated subjects who slept for five and 30 minutes, as well as a control group who did not nap. Those who napped for five minutes reported cognitive improvements that were comparable to those in the control group, suggesting the five-minute napping duration was insufficient for most.
Those who slept for 30 minutes experienced a period of cognitive impairment and grogginess in the period immediately after waking up from their naps. However, once the drowsiness subsided, the average 30-minute napper experienced cognitive improvements for roughly 155 minutes — the same period as the 10-minute nappers, who experienced little to no post-nap impairment.
In addition to napping duration, time of day is an important factor to take into account. Our bodies experience a natural drop in temperature between the hours of 2pm and 4pm each day. This signals the brain to produce melatonin, a hormone that induces feelings of sleepiness. Napping during these afternoon hours coincides with this period of natural drowsiness. We fall asleep more easily, and tend to feel more refreshed when we wake up — as long as the nap doesn’t exceed the 20-minute mark.
It’s also important to avoid napping close to bedtime. The general rule of thumb is to refrain from napping at any point in the three hours before you go to bed. Otherwise you may experience prolonged sleep latency.
Lastly, darkened rooms kept at a comfortable temperature are considered the best environments for napping. Rooms that are bright or exposed to the sun are not ideal because your circadian rhythm is based on natural light. Areas that are too warm or too cold can also interfere with your ability to get comfortable and fall asleep. The optimal temperature for sleep is 60 to 67 degrees Fahrenheit (or 15 to 19 degrees Celsius).
The bottom line: every sleeper is different, and the ideal napping duration will vary from person to person. However, for many adults, 10 to 20 minutes in the mid to late afternoon is all they need.