What exactly happens to your body when you fall asleep? During sleep, you go through a number of sleep cycles that allow your body to rest and repair itself. When you have a sleep disorder, one or more of these cycles may be disrupted in some way, causing your body to miss out on the restorative rest it needs to stay healthy. If you seek treatment with a sleep medicine specialist, he or she may discuss sleep-wake cycles with you when explaining your condition. Here is what you need to know.  

Stage One 

Stage one is the lightest stage of sleep and occurs as soon as you drift off. Your eye movements slow down and your brain produces slow waves that are associated with sleep. This part of the sleep cycle may last for as little as seven minutes, and because you aren’t resting deeply in this light sleep stage, it is easy to wake up from stage one sleep.

Stage Two 

During stage two, you fall a little deeper into sleep. The brain produces sleep spindles, which are bursts of slow waves that encourage your body to rest before slowing down. Although stage two is deeper than stage one, it is still not considered deep sleep. People who take 30 minute power naps usually wake up when they are in stage two sleep, since reaching this stage lets your body rest without the grogginess that can be associated with deeper rest.

Stages Three and Four 

Stages three and four of sleep are similar to each other. The body slowly moves into increasingly deep sleep, thanks to an increase in delta waves in the brain. There is no eye movement or muscle activity, while the body works to repair tissue, improve immune function, and boost your energy reserves. If you wake during these stages of sleep, you will feel tired and groggy.


The REM, or rapid eye movement stage of sleep involves an increase in brain wave activity. During REM, the brain takes the information it has stored from the previous day and files it into your memory so that you can access it later. Dreams usually happen during REM sleep. 

During an overnight sleep study at Sleep Dynamics in New Jersey, we can determine how much time you’re spending in each cycle during your nightly sleep. We use those results and other information to diagnose your sleep disorder. Call (848) 217-0240 to make an appointment.