"Massive"? The intervention group went from a mean AHI of 49 to a mean AHI of 37. While the control group went from 49 to 43. It's something, but it's still very much in the "severe" category, and I wouldn't call it "massive".
Proper CPAP usage would reduce this group's AHI to <2 events/hour.
Proper CPAP usage would reduce this group's AHI to <2 events/hour.