Post-CPAP sleepiness--a specific syndrome?

Following treatment with continuous positive airway pressure (CPAP), some patients with obstructive sleep apnoea (OSA) remain sleepy despite effective CPAP and attention to other diagnoses that can provoke sleepiness. It is unclear if this residual sleepiness is an irreversible result of their previous OSA and merits consideration for pharmacological treatment or simply because of the many and varied causes of sleepiness normally found in the community. We have measured levels of sleepiness, using the Epworth Sleepiness Score (ESS), in 572 patients on CPAP and compared them with a control group of 525 subjects from a community survey, which would have included the usual lifestyle reasons for sleepiness as well as any undiagnosed sleep disorders. There was no difference in the percentage of patients with an ESS >10 in the CPAP group compared with the controls (16.1 versus 14.3, P = 0.54). Thus, although there clearly are sleepy patients within the CPAP group, the prevalence is no higher than in the community. We question whether so-called 'post-CPAP sleepiness' should be regarded as any more abnormal and worthy of treatment than a 'normal' population. Post-CPAP sleepiness as a specific disorder may not exist.