Once you start to get into the world of Sleep Apnea, suddenly it seems that everyone has some form of sleep apnea.
While it is a fair statement that all sleep apnea patients snore, it is not true that all people who snore have sleep apnea. Normal healthy sleep does exist and below are some examples of each. I tried to include some sampled of all stages and transitions. Clicking on the image will give a poor resolutons, but the link beneath is much higher resolution, though it will take longer to load.
Little is known about the purpose of each sleep stage.
Below left is a picture of a person awake with their eyes closed. When you close your eyes you have Alpha waves throughout your brain that are 8-12 Hertz. Awake with eyes open isn’t quite as exciting as it is mixed cycle, but much smaller in amplitude.
Below center an image of Stage N1 sleep. Eyes are slow and rolling with low amplitude mixed frequency EEG (brain-waves). Typically about 5% of the entire night or less.
N1 sleep is really just thought of as being a transition to stage 2 (or N2) sleep. Slow rolling eye movements and vertex sharp waves are notable during this stage of sleep.
The image below right shows Stage 2 sleep, or N2 sleep. This is the most common stage in adults usually making up about 50% of the night. Key to this stage are sleep spindles and K-complexes shown in the example. Click the lettering for a higher resolution image. In this example the patient is using CPAP.
Below is a side by side comparison of Delta sleep (N3) in a Child and Delta sleep in an Adult. The child is on the left, the adult is on the right. Children spend about 50% or more of the night in Delta while Adults spend about 25% in delta. The older you are, the less delta you have. Human Growth Hormone is released during Delta. Delta is typically thought of as being physically restorative sleep where your body grows and makes repairs. With waves this slow, you can see why it is incredibly difficult to wake someone in Delta sleep. If you do, you see why they wake groggy.
There is some debate over people “dreaming” during Delta sleep. It appears that visions are seen during Delta sleep, but that these are more like fleeting images rather than dreams. Example: A REM dream is like watching video, where a Delta dream is like viewing a picture.
Below are several examples of REM sleep. “Sawtooth” waves (4-7 Hertz) are seen in REM sleep. There is mixed frequency low amplitude EEG (brain-waves). The Chin EMG is very low during REM and the most interesting and most noticeable are the REMs, Rapid Eye Movements. Some believe that these eye-movements are following the action of dreams.
It seems that REM is needed for memory and concentration. People deprived of REM sleep have been show to have difficulties with both memory and concentration. REM sleep makes up 25% of sleep in “normal” sleep in an adult. It’s about the same in children. Typically a person will go into REM after every 90 minutes of sleep. The first REM period is usually very short. (5-10 minutes) The last REM period can be an hour to 90 minutes.
During sleep studies it is not abnormal to miss your first REM period. Another interesting sleep study phenomenon is called “REM Rebound.” This is when a person with sleep breathing problems, such as obstructive apnea, is put on CPAP for the first time. They will often have incredible amounts of REM after that therotically making up for extreme REM deprivation. Two straight hours of REM is not uncommon in these situations.
An adult sleeper is expected to have a REM latency (time it takes to enter REM once they initially fall asleep) of 90 minutes. 60 to 120 minutes would be considered the limits of the normal range. It is normal for people suffering from depression to have a REM latency of 30 to 60 minutes.
Patients with Narcolepsy can have “Sleep Onset REM.” This is when someone who initially falls asleep will go directly into REM.