Endogenous Circadian System Attenuates Nighttime Vascular Endothelial Function in People With Untreated Obstructive...

Area of Science:

• Cardiology
• Sleep Medicine
• Circadian Biology

Background:

• Obstructive sleep apnea (OSA) is associated with increased cardiovascular events, particularly during the night.
• Vascular endothelial function, a marker of cardiovascular risk, is impaired in OSA patients.
• The endogenous circadian system may contribute to elevated cardiovascular risk in OSA.

Purpose of the Study:

• To investigate whether the circadian system drives nighttime impairment of vascular endothelial function in individuals with OSA.
• To determine if impaired vascular endothelial function during the biological night contributes to increased cardiovascular risk in OSA.

Main Methods:

• Twelve adults with moderate to severe OSA underwent a 5-day controlled circadian protocol.
• Researchers measured brachial artery flow-mediated dilation during scheduled wake periods to isolate circadian effects.
• The protocol separated circadian influences from behavioral factors like sleep, meals, and exercise.

Main Results:

• A significant circadian rhythm was observed in flow-mediated dilation and normalized flow-mediated dilation.
• Vascular endothelial function exhibited a trough around 3:00 AM, indicating impaired function during the biological night.
• No significant circadian rhythm was found in baseline arterial diameter.

Conclusions:

• The circadian system demonstrably impairs vascular endothelial function during the biological night in individuals with untreated OSA.
• This nighttime impairment may heighten vascular vulnerability and contribute to adverse cardiovascular events in OSA patients.
• Findings suggest a crucial role for the circadian system in the pathophysiology of cardiovascular complications in OSA.