All of us require sleep in order for our body and mind to regenerate. Researchers have also proven that people can perform memory tasks better after getting quality sleep. It’s true that our body relaxes when we sleep but have you ever wondered what really happens to our brain while we are unconscious and unaware of the outside world? Have you thought about why you’re having dreams at night? All of these have something to do with our sleep cycle.
A Sleep Cycle is the period of time it takes for an individual to progress through the stages of sleep. A complete sleep cycle takes an average of 90 – 110 minutes. Each stage lasts between 5 – 15 minutes.
What are the stages in the sleep cycle? During a whole sleep cycle, we experience two types of sleep. First is the “Non-Rapid Eye Movement” (NREM) or also known as the quiet sleep. It is composed of four stages.
- Stage 1: This is the part when we drift in and out of sleep and can still be awakened easily. Since we are only sleeping lightly on this stage, it is also where we experience sudden muscle contractions. This is the reason why we feel like falling sometimes.
- Stage 2: This is the stage when our body is preparing for deep sleep. It is when the eye movement stops and the brain waves becomes slower with only an occasional burst of rapid brain waves. Our body temperature also begins to drop at this stage.
- Stage 3: This is the part when we fall into deep sleep. The brain waves at this point are slow (also called slow delta waves) and are interspersed with smaller and faster waves. This is the stage where we can experience sleepwalking, night terrors, talking, and bedwetting. These are called “Parasomnias”.
- Stage 4: This is when we are in a deep sleep. The muscle activity at this stage is very limited and the brain produces extremely slow delta waves. There is also rhythmic breathing during this stage.
The other type of sleep is the “Rapid Eye Movement” (REM), also known as the active sleep. It is also the last stage of the sleep cycle. The REM stage is when the brain waves mimic activity during the waking state. The eyes remain closed at this stage, but it moves rapidly from side to side, which can be related to the intense dream and brain activity that is occurring.
NREM sleep and REM sleep alternates continuously through the night in a cyclical way. The first complete cycle of NREM to REM sleep lasts between 70 to 100 minutes and the three following cycles lasts about 90 to 110 minutes. An individual normally goes through 4 to 5 sleep cycles a night. The first 2 to 3 sleep cycles are spent longer in stages 3 to 4 of NREM and the final 2 to 3 sleep cycles are spent longer in REM stage.
Each stage of sleep in our sleep cycle fulfills a specific neurological and physiological function which are necessary to our body and mind’s health. This is the reason why when our sleep is disturbed, we tend to feel tired or groggy. Because the function of the stage where we were suddenly awakened was not fulfilled completely. This phenomenon is called “sleep inertia”. To avoid this, special alarm clocks have been invented and are set to wake up an individual during the period of light sleep, because the effect of sleep inertia on this stage is least acute. There are also some sleep time calculators available online that can help you calculate the exact time you should wake up when you sleep on a certain time.
Different ages have different sleep cycles. Adults usually sleep 8 hours a night and teenagers usually more than 9 hours. According to studies, 5 to 6 complete sleep cycles are needed to able to have a goodnight’s sleep. However, the number of hours we sleep still depends on our daily activities. If you weren’t able to complete 5 to 6 cycles of sleep, it is advisable to take a nap. If you’re up late and wasn’t able to get enough sleep, a fifteen to twenty-minute nap can help you recover from fatigue. In fact, even a 5-minute nap is beneficial based on research.
Being aware of our sleep cycles can help us create healthy sleeping patterns. The best sleeping habits should be consistent because it will allow us to stay on top of our life’s daily challenges.