Arousal from slow-wave sleep is often accompanied by feelings of grogginess and confusion. Waking people up during this stage is fairly difficult compared to the first two NREM stages. Your brain activity levels, heart and breathing rates, and body temperature will all reach their lowest points of the sleep cycle. The third stage of the cycle is composed of deep NREM sleep or slow-wave sleep.

Since these are light NREM stages, you can be aroused from sleep somewhat easily. 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. The sleep cycle of a healthy adult is divided into four distinct stages. 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. 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. 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. For most people, the ideal nap lasts 10 to 20 minutes. A primary key to taking a successful nap comes down to timing.

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.

Nap durations