The Four Stages of Sleep and What They Actually Do
Sleep better knowing how long each stage should last, what happens, and why you need to cycle through them several times
Hey folks: I will be offering several articles about good sleep, and how to get some, in the coming weeks (along with articles about physical fitness and mental health, of course). This article was first published on Medium, behind a subscriber paywall, and is drawn from Chapter 9 of my book, Make Sleep Your Superpower. It has been revised and updated to better stand alone here.
If you’d like to learn a whole lot more about how to make your days better, check out the book (available in paperback or Kindle version). The premise:
Right after air, water and food, sleep belongs in any hierarchy of needs for a person who hopes to thrive… Improving your sleep will make you better at everything you do, whether you’re a college student, an entrepreneur, an athlete, an artist, a parent, a teacher, a 9–5 worker or a 5–9 workaholic, a Millennial or a Boomer.
So before you nod off, let’s explore the basics of what happens when you sleep…
You don’t need to become an expert on rapid-eye-movement (REM) sleep to figure out how to get some, but a cursory understanding of the primary stages of sleep will illuminate why it’s so important to cherish efficient slumber, and why good daytime habits are crucial to successful nighttime sleep.
Yet because sleep remains somewhat mysterious, experts describe the stages, and what exactly occurs during each phase, differently. I’ve researched the many different explanations and whittled things down to the essentials.
For practical purposes, a general summary goes like this:
After your head hits the pillow, it might take anywhere from five to 20 minutes to nod off. There’s no correct amount of time, but it’s considered unusual if you fall asleep instantly or take hours. Then, at some point, the transition is nearly instantaneous: You’re awake, you’re awake, you’re awake, blink, you’re out.
On a good night, you’ll go through the following four stages in this order, anywhere from about four to seven times, with each making up the very rough estimate of total sleep time noted.
Light sleep: 45%
Deep sleep (slow-wave sleep): 25%
REM sleep (25%)
Each stage serves a different function in restoring the mind and body to prepare you for a new day. Quality, rejuvenating sleep depends not just on duration, but on cycling successfully through the stages multiple times. Disruptions during the night—or fitful sleep owing to too much booze, an underlying health condition or many other forms of sleep kryptonite—can rob you of crucial time in either or both the two most important stages: deep sleep and REM sleep. You’ll know you’re not sleeping well if you struggle to wake up or feel tired or irritable during the day. So let’s examine what happens in each stage, and how successful sleep can be your superpower.