This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. AIM 1: Examine the effect of CPAP treatment on SDB and sleep in patients with SDB and PDD. Hypothesis 1: SDB and sleep will improve with CPAP treatment (i.e., the number of respiratory events and the number of desaturations will decrease and sleep will become less fragmented with fewer arousals as measured by polysomnography [PSG]) as compared to shamCPAP treatment. AIM 2: Examine the effect of CPAP treatment on daytime sleepiness, cognition, overall quality of life and mood in patients with SDB and PDD. Hypothesis 2: Improved sleep (defined by fewer arousals in nighttime PSG) and reduction of SDB (fewer respiratory events and decreased numbers of desaturations) following CPAP treatment will result in less daytime sleepiness (as measured by sleep latency on the multiple sleep latency test and subjective reports on the Epworth Sleepiness Scale), improvement in cognitive functioning (particularly in the areas of attention/vigilance, executive functioning and psychomotor speed), fewer depressive symptoms and improved quality of life as measured by standardized questionnaires.