The Four Stages of Sleep

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There’s more to sleep than simply conking out for eight hours.

If you never realized this, well, we forgive you. After all, it seems rather uncomplicated: You sleep, you wake up, you repeat.

Photo used with permission from Jack Donaghy.

But let’s take a closer look at the sleep cycle. It consists of four main sleep stages, progressing from stage 1 through to REM. A night of sleep typically contains between three and five of these cycles, which each range in time from 90-110 minutes.

Stage 1: Light Sleep

The first stage is one of transition. You may drift in and out of light sleep without realizing it — perhaps during a Netflix marathon, for example. While your eyes and muscles gradually slow down, you may experience sudden muscle contractions. This is called a hypnic jerk, and is often accompanied by a falling sensation.

Stage 2: Onset of Sleep

About 50 percent of your nightly sleep time takes place in stage 2. Your eye movement stops and your brain waves lessen as you lose awareness of your surroundings. Your body temperature also begins to drop. This is still a relatively light sleep, during which it’s easy to awaken.

During a typical night, your body cycles through four stages of sleep. REM periods usually lengthen over the course of the night, while Stage 3 periods shorten in duration.

Stage 3: Deep Sleep

This is the deepest, most therapeutic sleep you’ll get all night. Breathing slows, blood pressure lessens and muscles relax. This is also when the body begins to repair itself, as hormones, including growth hormone, are released. Your body directs its blood supply to muscles, which aids in restoration.

If you awaken from deep sleep, it’s likely you’ll feel groggy or disoriented for up to an hour before you get your bearings. Ever heard of waking up on the wrong side of the bed?

Stage 4: REM Sleep

REM stands for rapid eye movement, an apt descriptor for this stage of sleep. Your eyes dart back and forth, your blood pressure increases and your heart rate and respiration become rapid and irregular. Brainwaves in this stage are similar to those exhibited while awake.

The body also loses some of its ability to regulate its temperature during this period, so abnormally hot or cold temperatures may negatively impact the quality of your sleep. Because of this, a mattress with built-in temperature regulation is a great choice, as it can help prevent disruptions in your sleep.

This is also the period during which you’re most likely to experience vivid dreams. Whereas your muscles relax during non-REM sleep stages, here they’re paralyzed in order to stop you from acting out dreams and injuring yourself. REM periods typically represent about 25 percent of your total sleep time, and gradually lengthen over the course of the night.

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