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Understanding Sleep Apnea: What Happens When You Stop Breathing

Sleep apnea is a sleep disorder where a person's breathing stops and starts repeatedly during sleep. These pauses can last from a few seconds to more than a minute, and they may happen dozens or even hundreds of times per night. When breathing stops, the body doesn't get enough oxygen, which jolts the brain awake. Most people don't remember these wake-ups, but they disrupt sleep quality significantly.

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There are three main types of sleep apnea. Obstructive sleep apnea (OSA) occurs when the throat muscles relax too much and block the airway. This is the most common type, affecting roughly 22 million Americans according to the American Academy of Sleep Medicine. Central sleep apnea happens when the brain doesn't send proper signals to the muscles that control breathing. Complex sleep apnea involves features of both obstructive and central types.

The signs of sleep apnea include loud snoring, gasping for air during sleep, waking up with a dry mouth, morning headaches, excessive daytime sleepiness, and difficulty concentrating during the day. Not everyone who snores has sleep apnea, but snoring combined with other symptoms warrants attention. Some people experience hundreds of breathing interruptions each night, though they may not realize it's happening.

According to research published in the American Journal of Respiratory and Critical Care Medicine, untreated sleep apnea affects approximately 34% of men and 17% of women between ages 30 and 70. Risk factors include being overweight, having a larger neck size, being male, and being older. However, sleep apnea can develop in people of any age, size, or gender.

Practical takeaway: Keep a sleep diary for one to two weeks, noting symptoms like snoring, witnessed breathing pauses (if you have a sleep partner), daytime tiredness, and morning headaches. Share this information with your doctor, as it can help with getting proper evaluation.

The Connection Between Sleep Apnea and Heart Disease

Sleep apnea and heart health are closely linked. When breathing stops repeatedly during sleep, oxygen levels in the blood drop. This causes stress on the cardiovascular system, forcing the heart to work harder. Over time, this repeated oxygen deprivation can damage heart tissue and blood vessels.

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Research shows that untreated sleep apnea raises the risk of high blood pressure, heart attack, and stroke. A study in the journal Circulation found that people with severe sleep apnea had a significantly higher risk of dying from heart disease compared to people without sleep apnea. The repetitive drops in oxygen levels trigger the release of stress hormones like adrenaline, which increases heart rate and blood pressure. Each night, a person with moderate to severe sleep apnea may experience hundreds of these episodes, creating a constant strain on the heart.

People with sleep apnea are more likely to develop atrial fibrillation, a condition where the heart's upper chambers beat irregularly. This irregular heartbeat increases the risk of blood clots and stroke. Additionally, sleep apnea disrupts the nervous system's ability to regulate blood pressure during sleep, leading to persistently elevated blood pressure even during waking hours.

The good news is that treating sleep apnea can reduce these cardiovascular risks. Studies show that using a continuous positive airway pressure (CPAP) machine—the most common treatment—can lower blood pressure and reduce the strain on the heart. People who treat their sleep apnea often see improvements in their overall heart health within weeks to months.

Weight plays a role in both conditions. Excess weight increases the risk of both sleep apnea and heart disease. When someone loses even 10% of their body weight, their sleep apnea symptoms often improve, and their cardiovascular function benefits as well.

Practical takeaway: If you have been diagnosed with high blood pressure or heart disease, ask your doctor about sleep apnea screening. The two conditions often occur together, and treating one may improve the other.

How Sleep Apnea Affects Your Heart: The Biological Process

Understanding how sleep apnea damages the heart requires looking at what happens during each breathing pause. When the airway closes and oxygen drops, multiple physical changes happen in quick succession. The brain detects low oxygen and signals an arousal response that partially wakes the person. Blood vessels constrict to redirect blood to vital organs, and the sympathetic nervous system activates, releasing adrenaline and cortisol into the bloodstream.

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These stress hormones cause an immediate spike in heart rate and blood pressure. In a single night, a person with severe sleep apnea might experience 50 or more of these spikes. Each spike forces the heart to pump harder and faster. Over months and years, this repeated strain can weaken the heart muscle, a condition called left ventricular hypertrophy, where the heart's main pumping chamber becomes thickened and stiff.

Sleep apnea also interferes with the endothelium, the lining of blood vessels. This lining normally produces nitric oxide, a substance that helps blood vessels relax and widen. The repeated oxygen drops and inflammation from sleep apnea impair this function, leading to stiffer, narrower blood vessels. This condition, called endothelial dysfunction, is a precursor to atherosclerosis, where plaque builds up in arteries.

The heart also depends on quality sleep to repair and restore itself. Sleep apnea fragments sleep, preventing the deep, restorative stages when the heart normally recovers. This means the heart is being stressed all night while also being denied the recovery time it needs. Additionally, sleep apnea disrupts normal blood clotting patterns, making the blood "stickier" and more prone to clot formation, which increases stroke risk.

Inflammation also plays a role. Sleep apnea triggers chronic inflammation throughout the body, including in the arteries and heart tissue. Research shows elevated levels of inflammatory markers like C-reactive protein in people with untreated sleep apnea. This inflammation accelerates plaque formation in arteries and damages the heart muscle itself.

Practical takeaway: Track your sleep quality and energy levels. Changes in how you feel upon waking—grogginess, fatigue, or a pounding heart—can signal that your heart and body are under stress. Sharing these observations with your doctor helps paint a complete picture of your health.

Recognizing Symptoms and When to Seek Medical Evaluation

The symptoms of sleep apnea often develop gradually, and many people don't realize they have the condition until a sleep partner notices the signs. The most obvious symptom is loud snoring that stops and starts, often followed by gasping or choking sounds as breathing resumes. However, not all people with sleep apnea snore, so the absence of snoring doesn't rule out the condition.

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Daytime symptoms include excessive sleepiness even after a full night of sleep, difficulty concentrating or remembering information, mood changes like irritability or depression, and morning headaches. Some people report waking up gasping for air or with a pounding heart. Others notice they need to urinate multiple times during the night, a condition called nocturia that occurs because sleep apnea affects the kidneys' ability to regulate fluid.

For people with existing heart conditions, sleep apnea can worsen symptoms. Someone with heart failure might notice increased shortness of breath or swelling in the legs. Someone with coronary artery disease might experience more chest pain or pressure. These worsening symptoms warrant prompt medical attention.

The process of getting evaluated typically starts with a visit to your primary care doctor, who may refer you to a sleep specialist. Your doctor will ask about symptoms, medical history, medications, and lifestyle factors. Some doctors conduct a screening questionnaire like the STOP-BANG scale, which assesses snoring, tiredness, observed apneas, blood pressure, body mass index, age, neck circumference, and gender.

If sleep apnea is suspected, the next step is usually a sleep study. A home sleep apnea test lets you sleep in your own bed while wearing a small portable monitor that measures breathing, oxygen levels, heart rate, and sleep position. For more complex cases, an in-lab sleep study at a sleep center may be recommended. During an in-lab study, you sleep in a comfortable room while sensors monitor your brain activity, eye movement, muscle activity, heart rhythm, breathing patterns, oxygen levels, and snoring.

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