Success in blinding to group assignment with sham-CPAP

This study evaluated the success of sham-continuous positive airway pressure (CPAP) as a placebo in a 4-week clinical trial of adults with sleep apnea. Participants (n = 23) were previously undiagnosed for obstructive sleep apnea, had no one in their household on sleep apnea therapy, and were willing to be randomly assigned to either active or sham-CPAP. Before final debriefing, participants were asked to "guess" their group assignment. When questioned, 10 of the 23 participants (44%) were incorrect in their guess of group assignment; 2 of these participants stated that their guess was "random." The active CPAP group's average usage was significantly longer when compared to participants on the sham device (293 ± 117 min/day vs. 188 ± 110 min/day, p = .046). The results suggest that participants remained blinded to group assignment and that sham-CPAP is an appropriate placebo control device. Participants' lower adherence to the sham device may be a potential problem that requires attention in the use of sham-CPAP as a placebo during clinical trials.