Not yet taking people in DenmarkNo phase

Heart and Brain Blood Flow in Obstructive Sleep Apnea

Key facts

Who runs it: Copenhagen University Hospital, Rigshospitalet
Where: Copenhagen and Glostrup Municipality, DenmarkSee the 2 sites
Trial code: NCT07913269
Status: Not yet recruiting
People taking part: 50 people, planned
Starts: 15 Nov 2026
Expected to end: 15 Nov 2028
Type of study: Observational, 2 groups
Record updated: 3 November 2026

Who can take part

Age: 18 years to 65 years
Sex: Women and men
Healthy volunteers: Can take part

The registry criteria, word for word

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Who can take part

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

Who cannot take part

Contraindication to MRI, including a pacemaker that is not MRI compatible, ferromagnetic implants, first trimester pregnancy, or severe claustrophobia
Previous stroke, intracerebral haemorrhage or intracranial surgery, severe depression, or psychosis
An unstable or seriously progressive medical condition, as assessed by a physician
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

Check if you might fit

Answer for yourself. This is not a decision: only the study team can say whether you can take part.

Are you between 18 and 65 years old?

Where in Denmark

Department of Diagnostic RadiologyCopenhagen, DenmarkContact: Adam E Hansen, MD, PhDNo longer taking part
Danish Center for Sleep MedicineGlostrup Municipality, DenmarkContact: Poul J Jennum, MD, PhDNo longer taking part

About the trial

What the trial wants to find out

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.

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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.

The 2 groups in the trial

Severe obstructive sleep apnea
Adults aged 18 to 65 years with AHI at least 30 events per hour. Participants undergo MRI at rest and during the Mueller and Valsalva maneuvers, real time flow measurements during spontaneous obstructive apneas, and 4D flow MRI during CPAP.
Controls
Adults aged 18 to 65 years referred for assessment of suspected OSA, with AHI below 5 events per hour. Participants undergo MRI at rest and during the Mueller and Valsalva maneuvers.