An additional issue to consider in any attempt to more precisely determine the treatment interval that results in normalized alertness is patient compliance with CPAP therapy. As this study shows, there is an immediate increase in alertness after only one night of CPAP treatment. This may serve as powerful motivation for compliance. Paradoxically, patients may also perceive their increase in alertness as sufficient reason not to strictly adhere to a program of CPAP treatment. This possible lack of compliance with therapy may help to explain why there was no significant difference in daytime alertness between 14 and 42 nights of treatment. In this study there was no objective measure of compliance, only a patient selfreport, and no validation of the accuracy of that selfreport.
If the question of patient compliance could be addressed, an interesting approach to increasing alertness would be to increase the time spent in bed by patients using CPAP. Once the sleep debt brought about by sleep fragmentation is resolved, extending time in bed would probably increase the level of alertness, as sleep extension studies have shown. Another interesting study would be to determine the time course of a return of symptoms of daytime sleepiness after successful treatment with CPAP but discontinuation of its use. How quickly would dysfunctional somnolence return once the blocking effect on sleep fragmentation provided by CPAP therapy is removed? The CPAP treatment provides a very clear operational model to examine the nature of the effects of sleep fragmentation. How does EDS progress as a function of the number of sleep fragmented nights? An experimental study of sleep fragmentation in normal subjects reduced alertness after only two nights of arousals. At what point does the chronic presence of sleep fragmentation produce the level of pathologic EDS seen in OSAS patients?