Sleep Disordered Breathing (SDB) is very complex breathing condition that destroys your slumber and endangers your health by two very prominent physiological processes:
Sleep Fragmentation: SDB is so disruptive because it constantly interferes with your brain waves as you attempt to sleep. Instead of remaining in deeper, restorative stages of sleep for much of the night, SDB forces you into lighter sleep stages and in the most cases, it triggers hundreds of little awakenings during the night that literally rob you of sleep. In fact, if you sleep 8 hours and suffer from moderate to severe SDB, chances are high you are only getting 4 to 6 hours of solid sleep.
Oxygen Fluctuations: SDB dramatically alters stabily of the oxygen your body receiveds into the body and transfers into your bloodstream. In a normal sleeper, oxygen levels are maintained in a surprisingly stable pattern. For, if the level were 94% (90 to 100% being the standard normal range), then this value could be maintained for minutes on end with minor or no fluctuations whatsoever. In most SDB cases, oxygen fluctuates all night long, often within a time span as short as a few seconds. In a 30 second interval (the standard interval we use in sleep studies), oxygen could start at 94%, drop to 91 in 10 seconds, go back up to 93$ in another 5 seconds, and then drop again to 89% in another 15 seconds. In more severe cases, these fluctuations deteriorate into what are known as desaturations, where the oxygen level drops frequently below 90% for 10, 20, 30 seconds or longer, before returning to the normal level above 90%. Sometimes oxygen drops even lower, particularly in REM sleep or when you sleep on your back.
These two components--sleep fragmentation and oxygen fluctuations/desaturations are the key to understanding the nature of SDB. Most importantly, it will help you understand why the term "obstuctive sleep apnea" (OSA) is a misleading term. Sleep apnea literally refers to the process in which you stop breathing for anywhere from 10 seconds or longer, amazingly up to 60 seconds in unusually severe cases. As you would expect, sleep disruption and oxygen desaturations are quite severe following an apnea.