Woman Sleeping

The 5 Sleep Stages: What Happens When You Sleep?


Comfort is knowing the science behind better sleep.

“There will be sleeping enough in the grave.” – Benjamin Franklin

In other words, “you’ll sleep when you’re dead”. You’ve heard that before, right?

This quote has been adapted and paraphrased in various forms since the 18th century. And while its lasting impact can’t be denied, it’s also pretty bad advice.

We’re all familiar with those who pride themselves on their ability to work 70 hours a week with minimal shut-eye. This isn’t an anomaly in today’s work force; many see it as a sign of success. As we try to keep pace with demanding office schedules, sleep is often the first thing to be sacrificed.

But the truth is that for those who burn the candle at both ends, they’re doing a disservice to their employers, colleagues, and to themselves.

“Sleep is not a luxury,” says Dr. James O’Brien, medical director of the Boston Sleep Care Center. “It’s a necessity for optimal functioning” (source).

Prior to the 1950s, professionals believed that our brains enter a passive shutdown mode when we sleep. We now know this isn’t true.

Sleep is a much more complicated activity. Every night our brains go through various predictable cycles. These cycles allow the brain to clear out accumulated toxins and repair itself from the previous day.

Knowing how these cycles work is crucial to understanding the importance of sleep and how it affects us on a day-to-day basis (source).

The 5 Stages of Sleep

During optimal sleep, our brain passes through a cycle consisting of five stages. As we transition through each stage, our brain catalogues memories and releases hormones. These hormones help regulate our mood, energy levels and cognitive ability. This process requires between 7 to 8 hours of uninterrupted rest, throughout which we typically experience four to five of these cycles, each lasting roughly 90 minutes (source).

Stage One

Your muscles begin to relax and your eye movements slow down. Your brain begins to produce alpha and theta waves. This is a light stage of sleep from which you can be easily awoken. You may also experience sudden muscle contractions, known as hypnic jerks, that jolt you awake.

Stage Two

Your eye movements stop. Brain waves slow down, punctuated by occasional sudden increases in frequency known as sleep spindles. Your body temperature begins to drop and your heart rate slows, preparing you for deep sleep.

Stage Three

Your brain begins to produce gentler delta waves as it enters “slow wave sleep.” Brain and muscle activity decrease as your body becomes less responsive to outside stimuli.

It’s during this stage that people may experience night terrors or sleepwalking. These behaviours, known as parasomnias, generally occur during the transition between non-REM and REM sleep (source).

Stage Four

The brain almost solely produces delta waves as you move into deeper more restorative sleep. During this stage, muscles and tissues are repaired, your immune system is boosted, and energy is restored for the next day.

Rapid Eye Movement (REM) Sleep

REM sleep begins around 90 minutes after you fall asleep, with the first stage typically lasting 10 minutes. As your sleep progresses the stages get longer, eventually lasting up to an hour.

This is also the stage of sleep when dreams occur. While the brain itself is very active during this time, the muscles become paralyzed. Your eyes move rapidly in different directions. Your breathing becomes irregular and your heart rate increases (source).

This stage also plays a vital role in learning and memory function. It’s during REM sleep that your brain processes and consolidates any experiences you’ve had during the day, allowing them to be stored in your long-term memory.

What This Means

When you interrupt your sleep cycle, you’re impeding your brain’s ability to move into deep sleep, and subsequently REM sleep. These are by far the two most important stages. Not only are they essential for physical renewal and hormone regulation, but without them you’re more likely to feel depressed, gain weight and get sick.

A 2008 poll conducted by the National Sleep Foundation found that those who sleep 6 hours or less per night are 41% more likely to be obese than those who sleep for 8 hours or more. The same poll also found that those who suffer from inadequate sleep are twice as likely to report difficulty concentrating (source).

Depriving your brain and body of REM sleep makes concentrating on a single activity much more challenging and greatly impedes your ability to make sound decisions. It also slows your cognitive ability and weakens your memory (source).

Not all sleep is created equal. The brain is a complicated piece of machinery, and sleeping for the proper amount of uninterrupted time is what allows us to perform at our best the following day.