On a google search I found some reference in how hypopneas are defined. They are the "H" part of the Apnea Hypopnea Index. It appears there may be A1 hypopneas with 3% oxygen desaturation, as well as B1 hypopneas which have 4% desaturation. I would expect the A1 definition to give a higher number than the B1.
In the UK the National Health Service will not treat mild (5-15 AHI) while they do treat moderate (15-30). In North America mild apnea is more likely to be treated/insured.
