A brief nap can be refreshing and restorative, especially if you are sleep deprived, but longer naps late in the day can negatively impact your sleep quality and duration. A primary key to taking a successful nap comes down to timing. For most people, the ideal nap lasts 10 to 20 minutes. Studies have also shown the best time to take a nap is in the early to mid-afternoon, when most people experience a natural decline in energy and alertness.
Homeostatic sleep pressure, also known as your sleep drive, is a reason why you feel energized after waking up and gradually become more tired as the day progresses. Aside from considering your natural circadian rhythm and sleep drive, timing your naps correctly also requires an understanding of sleep architecture and different components of your sleep cycle.
The sleep cycle of a healthy adult is divided into four distinct stages. The first two stages consist of light, non-rapid eye movement (NREM) sleep, during which your heart rate, breathing rate, body temperature, and brain activity will all gradually decrease. Since these are light NREM stages, you can be aroused from sleep somewhat easily.
The third stage of the cycle is composed of deep NREM sleep or slow-wave sleep. Your brain activity levels, heart and breathing rates, and body temperature will all reach their lowest points of the sleep cycle. Waking people up during this stage is fairly difficult compared to the first two NREM stages. Arousal from slow-wave sleep is often accompanied by feelings of grogginess and confusion.
The final stage, rapid eye movement (REM) sleep, is characterized by a spike in brain activity and erratic eye movements. Your heartbeat and breathing rate will increase toward their normal waking levels, and dreams are more likely to occur during this stage. During your first sleep cycle of a given night, REM sleep typically begins about 90 minutes after you nod off. Initial sleep cycles contain more slow-wave sleep, whereas cycles in the latter part of the night include more REM sleep.
If you nap in the morning, the sleep consists primarily of light NREM (and possibly REM) sleep. In contrast, napping later in the evening, as your sleep drive increases, will comprise more deep sleep. This, in turn, may disrupt your ability to fall asleep at night. Therefore, napping late in the day is discouraged.
Based on findings from various studies, around 10 minutes is considered the best nap duration. This length of time allows you to catch a quick rest without entering slow-wave sleep and feeling excessively groggy after waking.
One particular study evaluated subjects after they took five-, 10-, 20-, and 30-minute naps. Subjects who slept for 10 minutes reported the most improvements. They did not feel groggy or fatigued upon waking, and their overall cognitive performance after waking was strong. Moreover, they felt benefits from their nap for up to 155 minutes after waking. Those who slept for 20 to 30 minutes noted the same positive benefits from napping as those described above, but only after a 30 to 35 minute period of impaired alertness and performance. The five-minute nap did not produce many benefits for sleepers compared to those in the control group, who did not nap at all.
The time of day is also important for napping. Most sleep experts recommend napping no later than 2 pm. As discussed above, napping prior to the mid-afternoon results in a combination of light and REM sleep, whereas napping after 2 pm results in more slow-wave sleep. This may affect your ability to fall asleep at a reasonable time later that night, potentially disrupting your nocturnal sleep cycle.
Other tips for napping include: