Phenotyping Mechanistic Pathways for Adverse Health Outcomes in Sleep Apnea

Inclusion criteria: * Adults aged 21-80 years. * Participants with a previous diagnosis of moderate to severe obstructive sleep will be eligible to enroll and attend the baseline study. Patients with a total apnea-hypopnea index greater than 15 events/hr on the baseline study will be eligible for further participation. Exclusion criteria: * Current treatment for obstructive sleep apnea (including CPAP, oral appliances, supplemental oxygen). Patients must be untreated prior to the baseline visit. * Use of medications that might depress respiration (including opioids, barbiturates, benzodiazepines, and Z drugs, including zolpidem, zopiclone, eszopiclone, and zaleplon). * Active use of non-prescription opioids (e.g., cocaine, methamphetamine) * Uncontrolled medical problem or major organ system disease, which, in the opinion of the investigators (PI and Co-Is), would interfere with the evaluation of the subject (e.g., uncontrolled hypertension, unstable coronary heart disease, etc.). * History of congestive heart failure, renal insufficiency, systemic neurological condition that could affect respiration. * Sleep disordered breathing or respiratory disorders other than obstructive sleep apnea: * central sleep apnea (\>50% of respiratory events scored as central), * chronic hypoventilation/hypoxemia (awake SaO2 \< 92% by oximetry) due to chronic obstructive pulmonary disease or other respiratory conditions. * Other sleep disorders: periodic limb movements (periodic limb mo…