The long-term objective of this research program is to develop effective, precision-care models to improve the functional outcomes of Veterans whose hearing difficulties are not explained by traditional hearing loss. Determining the cause of these types of auditory processing deficits and selecting effective rehabilitation options poses a substantial challenge for clinicians. The present proposal aims to address whether auditory processing is affected by the presence and severity of another condition common among Veterans and wider the American populace: obstructive sleep apnea (OSA). The objectives of this proposal are to a). explore associations between peripheral and central auditory system function and indices of OSA severity in Veterans with normal hearing sensitivity, and b). to provide data necessary for the design of a full-scale Merit Award proposal addressing the utility of continuous positive airway pressure (CPAP) therapy to improve auditory function. The central hypothesis of the current proposal is that OSA is associated with measurable auditory processing deficits even when standard audiometric test results are within normal limits. During the course of the study, the central hypothesis will be tested in addition to gathering pilot data needed to inform a largescale study of CPAP therapy and auditory function by pursuing the three specific aims, including 1) Measure the strength of the relationship between AHI score and objective markers of central and peripheral auditory system function in Veterans with untreated sleep apnea, 2) Develop a predictive model of auditory functional capacity based upon AHI scores, and 3) Measure change in auditory function among patients prescribed CPAP therapies as a function of compliance with clinically recommended CPAP usage. We will identify and recruit Veterans who have recently been diagnosed with OSA via polysomnography (PSG) conducted at the Portland VA Medical Center (n = 45), as well as a group of healthy control Veterans of similar age (n = 10). Recruited patients will have a range of OSA severity based upon Apnea-Hypoxia Index (AHI) including mild, moderate and severe. Exclusionary factors include cardiovascular & cerebrovascular disease, diabetes, age greater than 55 years, and clinical hearing loss. All participants will complete a rigorous audiometric test battery including behavioral measures of auditory processing, physiological measures of cochlear, brainstem, and cortical responses to sound, and self-report measures of hearing handicap and function. The strength of relationships between these auditory functions and measures obtained via PSG will then be examines, including the AHI, oxygen desaturation index, hypercapnia load, and snoring amplitude. This data will be used to develop a model predicting auditory function based upon AHI score. Finally, OSA patient participants will repeat all auditory testing following two months of CPAP therapy. Changes in auditory capacity will then b...