There are three levels of severity of sleep apnea – mild, moderate and severe.
The difference between these levels is determined by the number of times a person stops breathing while sleeping.
There is a scale called the AHI scale (AHI stands for Apnea Hypopnea Index). It is simply the number of times a person stops breathing for 10 seconds or more, during an hour of sleep.
If a person stops breathing between five and 15 times in an hour, they have a case of mild sleep apnea.
If they stop breathing between 15 and 30 times, their case is moderate.
When a person stops breathing more than 30 times in an hour of sleep, they have a severe case.