Stages of Sleep and Sleep Cycles

The 5 Stages of Sleep:

Though there are typically 4 stages of sleep as the 4^th stage was eliminated by the sleep profession in the US in 2008, and was merged in stage 3. But to give you a full picture, we will separately define stage 4 as well.

Stage 1:

Often referred to as light sleep, this stage is the first step towards sleep. This is where you drift into sleep and also out of it, meaning you are not fully asleep and can be awakened easily. Your eyes movement and muscle activity start to slow down, and this is where people sometimes experience the sensation of falling from a height and then contraction of the muscle.

Stage 2:

This is where the real transition to deep sleep starts. Your heart rate starts to slow down, and your body temperature also starts to drop. You enter in light sleep.

Stage 3:

This is where you dive into the deep sleep. Your brain waves become extremely slow and people in this experience sleepwalking, bedwetting, nightmares, and sleep talking.

Stage 4:

The subject will still be in a deep sleep in this stage. It is harder to rouse people, and if they are awakened, they will feel disoriented for a few minutes. This is the stage where your body starts to repair itself; your tissues start to regrow, bone and muscle building starts as well.

REM Sleep:

You may call it the fifth stage of sleep, but its scientific name is REM (Rapid Eye Movement) sleep. It is the final stage of sleep, and brain waves start to mimic the activities of waking state which means your eyes start to move rapidly from one side to another while staying closed.

What is Sleep Cycle?

Simply put, sleep cycle is the total period of time it takes for a person to move through all 5 stages of sleep mentioned above. One important thing to note here is that the order of these 5 stages of sleep is not straight. This means the sleeper does not go from non-REM (stage 1 to 4) to REM sleep. The sleeper goes from light sleep to deep sleep and then reverts back to light sleep and then moves to the REM sleep. To eliminate any confusion, please refer to the example below:

The sleeper first moves from stage one to stage 2 (both are light sleep stages) then from stage 2 to stage 3/4 (these are deep sleep stages) then from these stages of deep sleep to the stage 2 and then stage 1 of light sleep and then finally to REM sleep.

Note: After the REM sleep stage, the sleeper returns to stage 1 (light sleep), and the cycle starts again.

Stages of Sleep Cycle:

• Waking Stage: This is where the person is in full consciousness and can answer intelligently. You can also call it Stage 0.
• Light Sleep: This is where stage 1 and stage 2 of sleep lie. The person transitions between waking and sleeping in the first stage and then drifts to light sleep which is stage 2.
• Deep Sleep: The deep sleep stage encompasses stage 3 and stage 4 of sleep. The brain waves become extremely slow especially in stage 4 which are recorded with electroencephalogram (EEG), a device to evaluate the electrical activity of the brain.
• REM Sleep: It can also be called Stage R. Brainwaves start to pick up the pace and eventually become similar to the waves when the person is awake. The sleeper witnesses most vivid dreams in Stage R.

What is Deep Sleep?

It is comprised of stage 3 and stage 4 of the sleep cycle. It is also called as delta sleep or slow wave sleep. During this stage, the person is so deep in sleep that it is a bit difficult to wake him up. This is where bedwetting, night terror, sleepwalking, sleep talking or vivid dreaming starts. This is the sleep where our growth hormone is released, and our body starts to recover. If you experience a tiring day, and you are able to get a deep sleep, upon waking up, you will feel fresh and active.

When Does REM sleep Occur?

The slow wave sleep which encompasses light and deep sleep occurs in the first half of the night and then comes the REM sleep in the second half of the night. The average time it takes for an individual to enter into REM sleep is 90 minutes after he falls asleep. As we talked above that the cycle from light sleep to REM sleep continues until you wake up, the first cycle that ends at REM sleep will last for about 10 minutes. And each successive REM cycle will last longer than its preceding REM cycle.

Changes in Sleep Cycle with Age:

There is a change in sleep cycles with the change in age. Less age means more REM sleep, and with the increase in age, timing of REM sleep decreases. For instance, infants typically spend about 50 percent of their sleep time in REM sleep while the adults spend about 20 percent in REM, 50 percent in stage 2 (light sleep) and the rest 30 percent in other three stages. And as the adults get older, their REM sleep timing will start to decrease.

What ever stage of sleep you are in, selecting a good matterss will improve your sleep patterns.