Circadian System Disruptions in Sleep Apnea Increase the Risk of Nighttime Cardiac Events

Dr. Joseph Mercola - Take Control of Your Health

Briana Mercola

Health & Fitness, Alternative Health

4.6 • 1.5K Ratings

🗓️ 16 December 2025

⏱️ 3 minutes

🔗️ Recording | iTunes | RSS

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Summary

New research shows that people with untreated sleep apnea experience a sharp nighttime drop in blood vessel function driven by the circadian system, increasing vulnerability to heart attacks and other cardiac events
In a tightly controlled sleep-lab study, participants' arteries showed their worst ability to dilate around 3:00 a.m., revealing an 82% decline in vascular function during the biological night
This impairment persisted even after adjusting for blood flow, sleep quality, and apnea severity, confirming the circadian system — not behavior or breathing events — directly weakens vascular health at night
The findings help explain why people with sleep apnea experience more nighttime cardiac events, contrasting with the general population's morning peak in heart attacks and sudden cardiac death
Researchers emphasize that understanding circadian timing may help refine cardiovascular treatments for sleep apnea patients, including optimizing medication schedules to enhance nighttime vascular protection

Transcript

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0:00.0	What if the most dangerous moment for your heart isn't when you wake up, but around 3 a.m.
0:05.0	when your blood vessels are at their weakest, and you don't even know it's happening.
0:09.0	Welcome to Dr. Mercola's cellular wisdom.
0:12.0	Stay informed with quick, easy-to-listen summaries of our latest articles, perfect for when you're on the go.
0:18.0	No reading required. Subscribe for free at Mercola.com for the latest
0:21.7	health insights. Hello and welcome to Dr. Mercola's cellular wisdom. I'm Ethan Foster, and today
0:28.3	we're exploring new research showing that circadian system disruptions in untreated sleep apnea
0:33.7	sharply reduce your arteries' ability to dilate during the biological night, raising
0:39.0	the risk of nighttime cardiac events.
0:41.7	I'm Alara Sky.
0:43.9	The study will unpack found that in adults with moderate to severe obstructive sleep apnea,
0:49.2	vascular function followed a 24-hour rhythm with a deep trough around 3 a.m.
0:55.3	Arterial dilation fell by about 82% from peak to low point.
0:59.8	That magnitude is meaningful and helps explain why heart attacks and arrhythmias in sleep apnea
1:05.2	often strike during sleep.
1:08.4	The design matters.
1:10.4	Participants lived for five days in a time-isolated sleep
1:13.7	laboratory without natural light or clock cues. They followed repeating five-hour 20-minute cycles
1:19.8	that rotated sleep, meals, and activity across every circadian phase. Meanwhile, the internal
1:26.5	clock free ran and was tracked by dim light
1:29.1	melatonin onset.
1:30.7	That separation lets you see biology apart from behavior.
	...

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