The hypnotic selected, zolpidem, has a relatively short duration of action. Since sleep apnea tends to worsen in rapid eye movement sleep, which dominates the last third of the night, the medication may be wearing off at the time when the patients are having the most difficulty. A longer-acting medication might be a more suitable choice if the goal is to increase CPAP compliance. With only 24 subjects, the study may have been underpowered. The hypnotic chosen, zolpidem, compared to placebo increases total sleep time by approximately 20 to 30 min. However, the power calculation described looked for a 1-h difference in total sleep time. Subjects were only administered 14 tablets that they could use any time over 28 days. So at least half of the time all the groups were equal since none of the subjects were taking a pill. We should not be completely surprised that the groups ended up with similar results. Nightly use of the hypnotic agent during the entire study period may have led to different results. This may be supported by the data on Table 2, which showed in the first 14 days the hypnotic group is doing better than the placebo group.