Stages of the Sleep Cycle

•             N1 – N1 is considered the first stage of cycle. This is also classified as light sleep. This is where the transition from being awake to falling asleep occurs. People who are in this stage are easily awoken. In fact, people who are awoken in this stage will not even consider that they were asleep. This is also the stage where jerky movements of the leg or feet occur while falling asleep. These characteristics are all considered normal.

•             N2 – Just like N1, N2 is also considered as light sleep. It is also easy for people to be awakened in this stage. However, there are significant changes that draw people closer to sleep. The heart rate begins to slow down and the body temperature also begins to decrease. The brainwave patterns will also show activities that are related to sleep such as the sleep spindles and the K-complexes. During the N1 and N2 stages, it is very unlikely to have dreams.

•             N3 – The N3 part of NREM is considered to be the deepest phase of sleep. This is why it is called as the deep sleep stage. Just like the two previous stages, N3 can also be recognized by the brainwave patterns produced. These patterns are quite slower compared to brainwaves produced while awake. Unlike N1 and N2, people in this stage are very hard to wake. It usually takes a loud alarm clock to do the job. Once awake from N3, it is common for people to experience grogginess. This is a sign that the person was awoken during deep sleep. Since the body is not paralyzed in any of these three stages, it is common for some people to experience sleep abnormalities such as parasomnia or night walking, teeth grinding and night terrors.

A normal sleep cycle will last for approximately 90 minutes for an adult. This cycle will repeat for about 4 to 6 times in a night. It is important to know that cycles vary from one person to another. The time for a cycle to complete will be static; however, the range will be from 90 to 100 minutes.  There are several techniques to figure out a person’s sleep cycle. This is because the phases of sleep will be different or unique for everyone including the stages in between the cycles. A regular person will experience all the cycles but in his or her own way and schedule.