What happens during sleep | ResMed
What happens during sleep?

What happens during sleep?

Wondering what happens during sleep? Think of your body like a factory. As you drift off to sleep, your body begins its night-shift work:

  • Healing damaged cells
  • Boosting your immune system
  • Recovering from the day's activities

We all know the value of sleeping well, and we've all experienced the feeling of being refreshed after a good night's sleep (and the feeling of fatigue after a poor night's sleep). But even though we know this, in our busy society, many of us are not getting the quality six to eight hours of sleep our bodies need.

Understanding the sleep cycle

Understanding what happens during sleep also means understanding the sleep cycle. During the night, our bodies cycle through two recurring phases of sleep: REM (rapid eye movement) and NREM (non-REM or non-rapid eye movement). Both phases are important for different functions in our bodies.

If the REM and NREM cycles are interrupted multiple times throughout the night - either due to snoring, difficulties breathing or waking up frequently throughout the night - then we miss out on vital body processes, which may affect our health and well-being not only the next day, but on a long-term basis as well.1

What happens if you don't get enough sleep?

If your body doesn't get a chance to properly recharge (by cycling through the two phases of sleep, REM and NREM), you're already starting the next day at a disadvantage. You might find yourself:

  • Feeling drowsy or moody1
  • Struggling to take in new information at work, remembering things or making decisions2
  • Craving more unhealthy foods, which could cause weight gain1,2

If this happens day after day, night after night, you can imagine the strain it would place on your, body and overall health.3 Find out how to talk to your doctor about your sleep habits.


  1. Palnitkar G, Zimmerman S, Cistulli P. Sleep apnea in adults: identifying risk factors and tailoring therapy. Medicine Today 2012, 13(8):14-23
  2. Greer SI, Goldstein AN, Walker MP. The impact of sleep deprivation on food desire in the human brain. Nat Commun. 2013;4:2259.
  3. Mansfield DR, Antic NA, McEvoy RD, How to assess, diagnose, refer and treat adult obstructive sleep apnea: a commentary on the choices. Sleep Disorders. MJA 2013; 199: S21–S26