Obstructive Sleep Apnea (OSA) and Metabolic Syndrome: Role of Oxidative Stress

Inclusion Criteria: * Nonsmoker for at least 6 months * No history of movement disorder during sleep, or circadian rhythm disorder * No excessive daytime sleepiness * No history of chronic insomnia, mood or affective disorders or other psychiatric disorders * Participants maintain a regular sleep-wake pattern with an estimated sleep time between 6.5 and 10 hours per night * Ability and willingness to avoid meat with its juice (gravy), cured or smoked foods and green leafy vegetables, fruit and fruit juices, food products or vitamin supplements containing vitamin C and E supplements for at least 1 day prior to and during the study periods * Consumption of less than 1 alcoholic beverage per day * Ability to understand the study and sign the informed consent * Not currently pregnant * Live within 45 miles of the study site * No uncontrolled hypertension (blood pressure greater than 150/100) * Willingness to avoid caffeinated beverages and food during the study protocol period Participants With Sleep Apnea: * Diagnosis of severe Obstructive Sleep Apnea and Hypopnea (OSAH) (RDI greater than 25) and initiation of positive airway pressure therapy more than 1 month before enrollment * Must have had an adequate clinical titration of positive airway pressure therapy * On positive airway pressure for at least 1 month with adherence of more than 5 hours of use per day with no history of snoring, no excessive daytime sleepiness and no reported observed apnea episodes on positive airway pressure * Willing to sleep with and without positive airway pressure therapy as required by the study protocol Exclusion Criteria: * History or physical examination evidence of active coronary artery disease, heart failure, cardiomyopathy, syncope, potentially life-threatening arrhythmia, stroke, transient ischemic attack, neurologic impairment, renal, hepatic or thyroid disease (unless on stable thyroid replacement medication); history of diabetes mellitus; history of cancer within the past 10 years (other than basal cell carcinoma), venous thrombosis, or collagen-vascular disease or other condition that the investigators believe may be exacerbated by participation in the stud * History of awakening with angina pectoris * Currently taking medication for mood or affective disorders or that affect heme metabolism, autonomic nervous system or sleep architecture, or prescribed nitrates or corticosteroids * Physician-diagnosed Alzheimer's or non-Alzheimer's dementia * Previous surgery for sleep apnea * Hematocrit less than 32 * Use of a hearing aid in one or both ears * History of a bleeding disorder, abnormal bleeding, or known adverse reaction to heparin * Inability to obtain venous blood or a low likelihood of obtaining venous access as required in this protocol * History of migraine of a nature, frequency, and severity that, in the investigators' judgement, may be precipitated by participation in the protocol * Presence of a potentially life-threatening dysrhythmia on the clinical diagnostic PSG * History of motor vehicle accident due to falling asleep; not currently employed as a driver in the transportation industry or an airplane pilot * Lipid-lowering agents for participants without a history of sleep apnea * Individuals on positive airway pressure therapy for sleep apnea must not have lost more than 10 pounds of weight since starting this treatment