SleepusInterruptus wrote:I've read that up to 5 apnea events per hour is considered normal. But
a sleep cycle takes about 90 minutes, so how could one have a normal
sleep cycle when it gets disrupted every 12 minutes?
Here ended the first lesson regarding Sleep Apnoea
Sorry for joking, but that is exactly what happens to untreated sleep apnoea sufferers...........they have disrupted sleep architecture (name for the total number of cycles per night).
Each sleep cycle takes approx 90 minutes (up to 110 minutes), and during a typical nights sleep we have anywhere between 4 and 6 cycles............to make up our sleep architecture. In a perfect world our sleep time is spent in different stages (Non REM Sleep and REM (Rapid Eye Movement) Sleep). During Non REM Sleep we have Stage N1, Stage N2 and Stage N3, then REM Sleep. Stage N3 Sleep is our deepest sleep and gives us our most restful/restorative sleep. During REM Sleep we have vivid dreams and a lot of brain activity...........needless to say there is also a lot of eye movement, and our body goes into paralysis (some say to stop us living out our dreams). You can also dream during Non REM Sleep, but these dreams are not as vivid as those in REM Sleep.
Typical (perfect) Sleep Architecture is as follows:
These percentages are averages and there is room for manoevre......age factors etc.
The usual progression is Stage N1 to Stage N2 to Stage N3, back to Stage N2 and then on to REM Sleep. Typically we achieve our first encounter with REM Sleep after about 80/90 minutes......this doesn't last too long, but as we clock up the cycles the time spent in REM Sleep gets longer.............with the longest period of REM Sleep achieved shortly before we wake up.
Untreated sleep apnoea sufferers, because of the micro awakenings usually have an extended period in Stage N2.....with very little or even no Stage N3 and often little REM Sleep. The lack of Stage N3 sleep is the usual cause of Excessive Daytime Sleepiness.
Once we get treated and get our breathing into shape, our sleep architecture usually improves and gets back to normal.
Sorry............should have answered your question first.........up to 5 events per hour is considered normal and shouldn't have a huge effect on sleep quality. Obviously at 5, things are borderline. There is another event called a Hypopnoea.....OSA, has a full title of Obstructive Sleep Apnoea Hypopnoea Syndrome. The Hypopnoea (laymans definition) is like a mini apnoea, but with oxygen desaturations, hence the term AHI (Apnoea Hypopnoea Index).......which if below 5 is considered normal..............I've probably totally confused you now
Hope this helps.