The objective of this study is to examine the relative importance of acquiring health status information on a sleep apnea patient's functioning and quality of life by partners as proxy raters. Sleep apnea is a common sleep disorder and it is estimated to affect 2-4% of middle-aged adults. This disorder is characterized by frequent episodes of upper airway collapse, which is associated with nocturnal oxyhemoglobin desaturation, and daytime sleepiness. Without treatment, patients with sleep apnea often report a general impairment in their daily functioning and demonstrate several neurocognitive deficits including decrements in attention, vigilance, and memory. Several studies have shown an impaired quality of life in patients with sleep apnea by use of generic and disease-specific quality of life measures. Clinical experience suggests that patients with sleep apnea often underreport their symptoms. The cognitive dysfunction that accompanies sleep apnea may, in part, be responsible for this under-reporting. Moreover, patients gradually become accustomed to the impaired state and, therefore, cannot discern the overall impact of underlying disease on their functional status. In this situation, the decision to seek medical attention is often initiated by a proxy, usually the spouse. Proxy interviews reveal not only the lack of agreement between subjective and observed quality of life, but also the impact that the disease has on the proxy's quality of life. As ongoing and future studies examine the impact of sleep apnea on quality of life, we need to determine whether self-report is an accurate means for assessing quality of life in sleep apnea. Studies in other medical disorders that have associated cognitive dysfunction have shown that proxy-reported quality of life might provide a better substitute of the overall impact of the disease. Such analyses have not been previously done for patients with sleep apnea. Therefore, the primary objective of this proposal is to examine the level of agreement between self- and proxy- reported quality of life in patients-with sleep apnea. We hypothesize that there will be a lack of agreement between self- and proxy-reported quality of life in patients sleep apnea and that proxies will report a measurable decrement in their own quality of life that will improve after the patient has been initiated on treatment. A consecutive sampling scheme will be employed and a total of 150 pairs will be enrolled in the study. Patients and their proxies will complete a battery of quality of life instruments at baseline and 1-month after initiation of treatment with continuous positive airway pressure (CPAP). In addition, at baseline and 1-month follow up, information on disease severity, sleepiness, psychomotor vigilance functioning and CPAP adherence will be obtained for each patient. Proxies will assess their own quality of life with a generic measure at baseline and at 1-month follow up. Statistical analyses will include bivariate and multivariate analyses including Pearson Correlation, Kappa, and Intraclasss Correlation Coefficient calculations, linear and logistic regression. This study will provide the first systematic evaluation of proxy quality of life reporting in sleep apnea, and the completion of this study will increase our knowledge concerning the potential impact of proxy- generated data on study outcomes in sleep apnea research.