Heart and Brain Blood Flow in Obstructive Sleep Apnea

Obstructive sleep apnea causes repeated pauses in breathing during sleep. Breathing efforts against an occluded airway may change how blood flows through the heart and how blood drains from the brain. This study will examine these changes in 25 adults with severe obstructive sleep apnea and 25 adults without sleep apnea, aged 18 to 65 years. Participants will attend a screening visit and one magnetic resonance imaging (MRI) visit. MRI will measure blood flow in major vessels in the chest, neck and brain at rest and during brief, standardized breathing maneuvers. Participants with sleep apnea will also be studied during obstructive apneas while sleeping in the scanner, and during continuous positive airway pressure (CPAP), which keeps the airway open. The main objective is to quantify changes in blood flow rate and peak blood velocity before, during and at the end of obstructive apneas. The study will also compare responses to breathing maneuvers and resting blood flow between groups, and assess changes associated with CPAP in participants with sleep apnea. Secondary brain MRI outcomes are total perivascular space burden, burden in the basal ganglia and centrum semiovale, and the DTI ALPS index. BrainAGE, the difference between estimated brain age and chronological age in years, is an exploratory outcome. These MRI markers are compared between groups at baseline and after CPAP treatment.

Inclusion Criteria: Both groups * Age 18 to 65 years. * Able to provide informed consent OSA group • Severe OSA confirmed by a diagnostic sleep examination, with AHI at least 30 events per hour. Control group • Referred for assessment of suspected OSA, with a diagnostic AHI below 5 events per hour. Exclusion Criteria: * Contraindication to MRI, including a pacemaker that is not MRI compatible, ferromagnetic implants, first trimester pregnancy, or severe claustrophobia. * Significant cardiac disease, including left ventricular ejection fraction below 40%, myocardial infarction within the previous 3 months, or untreated arrhythmia; atrial fibrillation; or pulmonary hypertension that may affect flow measurements. * Previous stroke, intracerebral haemorrhage or intracranial surgery, severe depression, or psychosis. * An unstable or seriously progressive medical condition, as assessed by a physician.