To Dr. Greenburg's salient comments, I wish to add that it is critically important to know that some sleep apnea may appear to be mild, but when tested with more advanced breathing sensors, the condition may actually show up in a form called "Upper Airway Resistance."  The importance of UAR cannot be overstated,because it worsens the severity of sleep apnea.  Also, because many sleep labs in the USA still do not account for this more subtle breathing disturbance, there is a greater chance of actually missing the diagnosis of sleep-disordered breathing.

My new book, Sound Sleep, Sound Mind, describes a great deal of information about UAR, and you can learn more about this important component of sleep breathing at my website www.sleeptreatment.com.