What Are The Different Stages of Sleep?

What Are The Different Stages of Sleep?

You may have heard the terms REM phase of sleep, sleep cycle and sleep stage discussed before, but perhaps not fully understood what they mean or why they’re important.

Understanding the five stages of sleep is essential as each stage benefits your body differently, from memory consolidation to cell repair to hormone regulation. And, a healthy sleep routine is not just about getting enough hours of shut-eye; it’s also about fully experiencing the five sleep stages every night.

So, what are the different stages of sleep, how are they characterised and why are they important? In this blog post, we’re going to tackle those questions and share our tips on how you can improve your sleep cycle.  

What are the Five Stages of Sleep?

Stage 1:

The first stage of sleep is the lightest and is often considered the transitional phase. It also tends to be one of the shortest sleep stages, as most people will remain in stage one for no more than ten minutes. During phase one, you’re easiest to wake.

In stage one, your body begins to relax, getting ready to unwind and fall asleep. You begin drifting off and slowly losing consciousness.

Your muscles may start twitching. And, it’s common to experience the sensation of falling in this stage followed by sudden muscle contractions.

Stage 2:

Stage two is also considered a phase of light sleep, but it tends to last longer than stage one and tends to last for about twenty minutes. It’s also the sleep stage that most adults spend the most time in. Approximately 50% of time asleep is spent in stage two. 

In this stage, your core body temperature will begin to drop, your heart rate gradually slows down, and your muscles become more relaxed.

Your brain is also less active; your brain waves slow down, except for intermittent spikes of rapid brain wave activity known as sleep spindles.

It is believed that sleep spindles are important for memory formation and long-term memory consolidation. As a result, stage two becomes increasingly important as we grow older.

Stage 3 & 4:

The third and fourth stages of the sleep cycle are where deep sleep occurs. Collectively, they are considered the slow-wave sleep stages because your brain waves slow down. These slower waves are known as delta waves.

Stages three and four have similar characteristics, however when you transition from three to four, the number of delta waves your brain produces increases, and the number of faster brain waves decreases.

During these phases of deep sleep, your muscles become fully relaxed, and you become difficult to wake. If you do wake up from deep sleep, you’re likely to feel very groggy for some time afterwards.

Getting enough deep sleep is vital for your energy levels and mood. It is during this phase that our body re-energises itself, which is why you’ll feel groggy if you’re woken up.

Your body goes through many changes during deep sleep. Your blood pressure, heartbeat, core body temperate and breathing rate all fall during this stage. Your body also becomes immobile, and your eye movement stops.

However, your muscles are still functional, which helps to explain why sleepwalking and bedwetting are most common during the fourth stage of sleep.

Most importantly, deep sleep is critical for your overall health and wellbeing. Important hormones are released, including the human growth hormone, which aids development and the leptin hormone which regulates your appetite. Your blood sugar levels and metabolism are also regulated, and your immune system is strengthened.  

Phases three and four see your body repairing and healing itself. Cell repair and regeneration occurs in the muscles and tissues, and more blood flows to your muscles to aid in repair. This makes deep sleep especially important for anybody who is very active, has overexerted themselves or has injured themselves. 

Stage 5:

The final stage of sleep is also known as the REM phase of sleep. REM stands for ‘rapid eye movement’. Usually, you’ll enter the REM phase of sleep about 90 minutes after you drift off.

As the name suggests, your eyes move around rapidly behind your eyelids while you are in the REM phase of sleep. Your brain is also extremely active during this phase, which explains why this is when you’re most likely to dream.

Your blood pressure, breathing and heart rate will creep back up to near-waking levels. However, your voluntary muscles are extremely relaxed.

Getting enough REM sleep is believed to be vital for pain perception, processing new memories and learning new information.

The Sleep Cycle Explained

It may seem unusual, but when you sleep, you don’t typically transition through the five stages in sequence.

You’ll always start in stage one, before transitioning to stages two, three and four. However, you then tend to regress to stages two or three, before moving into the REM phase of sleep.

A healthy sleep routine will see you transition through the stages about four to six times throughout the night. If you don’t get enough quality sleep, you’re unlikely to fully experience every stage during a night. And, as each stage has different benefits for your body, mood and brain, if you don’t transition through the five stages properly, you’ll deprive your body of its needs.

Adults need about eight hours of sleep per night, and even if you feel like you’ve achieved that, you may still wake up feeling tired and groggy. This might suggest you have not properly cycled through the deep sleep stages or REM phase of sleep.

To improve your quality of sleep, we recommend investing in a comfortable, high-quality mattress that suits your needs, and replacing your mattress if need be. Your mattress should be of the right size and firmness to give you the best chance of sleeping properly.

We also recommend establishing a solid night-time routine, avoiding alcohol and caffeine before bed, switching off screens, and making your sleep environment as dark as possible.

For more advice on finding the right mattress for your needs and tips on how to improve your sleep habits, take a look at our blog.