FIG. 16:  On the basis of the evidence outlined in the previous Figures, the question arises as to whether treating asymptomatic patients with OSA is of any benefit.  Does it reduce cardiovascular risk even if it does not change symptoms? 

This Figure shows the results from a randomized trial by the Spanish Sleep and Breathing Network that attempted to answer this question.^[8]  The trial enrolled 723 patients with moderate-to-severe OSA, an AHI ³20, and an ESS <10, but who did not report sleepiness.  They were randomized to either CPAP or to a control group that did not receive CPAP.  Patients were followed for new-onset cardiovascular events over a period of up to 6 years. 

Although there was a trend toward fewer cardiovascular events in the CPAP treated group, the difference between CPAP and no treatment was not significant.  Moreover, 70% of these events were simply new onset hypertension, whereas for the 30% of events that where hard cardiovascular events there was no difference between the two groups.  Thus at the present time there is no evidence from randomized clinical trials that treating even moderate-to-severe OSA in asymptomatic patients reduces cardiovascular events.  One caveat might be that this trial was underpowered, with only 723 patients, whereas the average pharmaceutical trial in this field usually enrolls 2000–4000 patients.