In the randomized phase , the mean AHI score did not differ significantly from the 12-month score in the nonrandomized phase among the 23 participants in the therapy-maintenance group ( 8.9 and 7.2 events per hour , respectively ) ; the AHI score was significantly higher ( indicating more severe apnea ) among the 23 participants in the therapy-withdrawal group ( 25.8 vs. 7.6 events per hour , P < 0.001 ) .