Sleeping seems pretty straightforward; all that happens is that the body and brain shut down for a while and give themselves a chance to recover from a busy day, right? Not exactly! There’s a lot more activity going on than you’d think during your nightly slumber. Everyone goes through multiple sleep cycles each night – usually 4 or 5, assuming you’re getting enough rest. Here’s the truth of what happens to your body while you’re snoozing.
Stage One: “Light” Sleep
There are two main parts of the sleep cycle: NREM (non-REM sleep) and REM (rapid-eye movement). The first three stages fall under the NREM category.
During the first stage, eye movements begins to slow down, and the brain starts producing alpha and theta waves. This is light stage sleep where you can still be awakened fairly easily; if you’ve ever dozed off only to awaken a few minutes later, it means you didn’t get further than this stage.
Stage 2: Defined NREM Sleep
This is actually considered the first quantifiable stage of NREM sleep. While stage 1 is usually brief and typically lasts for about 7 minutes, stage 2 is much longer and can take up 40 to 60% of your total sleep time. At this point, brain waves are continuing to slow down, but bursts of activity known as sleep spindles still occur; these spindles are thought to help protect the brain from being awakened prematurely.
Stage 3: Deep Sleep
Once you move on to stage 3, the brain will start producing delta waves. Your body becomes less responsive to external stimuli, making it much more difficult for someone else to wake you up. Deep sleep is considered the “restorative” period of sleep; this is the body’s chance to repair damaged muscles and tissues, enhance the immune system, restore energy levels and – for younger sleepers – stimulate growth and development. Throughout the night, you’ll spend less time in stage 3 during each successive sleep cycle and more time in the fourth and final stage.
Stage 4: REM Sleep
Most adults reach REM sleep roughly 5 to 6 times a night, and at this point the brain is a lot more active; your eyes start to jerk in different directions, your heart rate and blood pressure increase, and breathing becomes much faster and more irregular. Most notably, it’s at this stage that most dreaming occurs.
REM sleep is when the brain processes the information from the previous day and stores it in long-term memory. You spend more and more time in REM sleep as the night goes on, which is why you’re likely to be having a dream when you wake up.
It’s important that you spend enough time in deep sleep and REM sleep each night in order to maintain good health; if something’s continuously disrupting your night’s rest, you won’t complete the sleep cycle enough times and thus won’t get the full benefits of these later stages. If you don’t think you’re getting enough z’s, speak with your sleep dentist to try and determine whether you have a disorder such as sleep apnea.
About the Author
Dr. Keana Fedosky helps patients suffering from poor quality sleep due to sleep apnea at his practice in Plano, Sleep Rehab. He has 20 years of experience in using oral appliance therapy to help people breathe easier at night, letting them enjoy a deep sleep – and letting those nearby enjoy a reprieve from loud snoring! To schedule an appointment, visit his website or call (972) 753-3737.