Sleep apnea: Can it cause heart disease?

Sleep apnea, along with its most common symptom, snoring, is more than just annoying. Some evidence suggests sleep apnea increases your risk of heart disease.

Sleep apnea and its most common symptom — loud snoring — have long been viewed as a nuisance. Just ask someone who has to share a room with a loud snorer if sleep apnea is a problem. But there's growing evidence that sleep apnea isn't just annoying; it can be bad for your heart, too.

You've probably heard about the usual problems associated with sleep apnea, such as feeling tired during the day. But sleep apnea can have more serious health effects, such as increasing your risk of high blood pressure and possibly heart failure, stroke, an abnormal heart rhythm (atrial fibrillation) and heart attacks.

What is sleep apnea?

Sleep apnea is a sleep disorder in which your breathing stops or gets shallow temporarily. These pauses in your breathing can occur dozens of times each hour while you sleep.

Sleep apnea occurs in two main types:

Obstructive sleep apnea. This is the more common form. It occurs when the muscles in the back of your throat relax. When the muscles relax, your airway narrows or closes as you breathe in, and breathing momentarily cuts off. This lowers the level of oxygen in your blood. Your brain senses this and briefly rouses you from sleep so that you reopen your airway. This awakening is usually so brief that you don't remember it.
Central sleep apnea. The far less common form of sleep apnea, central sleep apnea occurs when your brain fails to transmit signals to your breathing muscles. You may awaken with shortness of breath or headaches.

Sleep apnea and the heart

Virend Somers, M.D., is a researcher at Mayo Clinic, Rochester, Minn., who studies the potential link between sleep apnea and heart problems. "This area of research into the possible link between sleep apnea and heart disease is very much an emerging field of study," Dr. Somers says.

Dr. Somers and other researchers think sleep apnea may affect some forms of heart disease because of the drop in oxygen that occurs during sleep apnea. When your oxygen level drops, your carbon dioxide level increases. Your brain senses trouble and tells your body to release adrenaline-like substances into the bloodstream — the so-called fight-or-flight reflex — which increases blood pressure, thus the link to sleep apnea and high blood pressure.

Because of low oxygen, your body also releases other substances that can eventually damage the lining of your body's blood vessels, and it's this damage that might eventually cause or worsen high blood pressure and other forms of cardiovascular disease or heart problems. These include:

High blood pressure. Sudden drops in blood-oxygen levels that occur during sleep apnea increase blood pressure and strain the cardiovascular system. About half the people with sleep apnea develop high blood pressure (hypertension). "The only thing we can say for certain right now is sleep apnea increases your risk of high blood pressure," Dr. Somers says. While high blood pressure itself increases the risk of various forms of heart disease, there's speculation that sleep apnea also plays a more direct role in heart disease.
Heart failure. Sleep apnea may increase the risk of heart failure because of the swings in blood pressure that occur during sleep apnea. This, combined with reductions in oxygen to heart tissue, might damage heart muscle. If you already have heart failure, this repeated stress to the heart might make things worse.
Heart rhythm problems (arrhythmias). Arrhythmias occur when the electrical impulses in your heart that coordinate your heartbeats don't function properly, causing your heart to beat too fast, too slow or irregularly. One of the more common types of arrhythmias thought to be associated with sleep apnea is atrial fibrillation. This occurs when the heart's two upper chambers (the atria) beat chaotically and irregularly — out of coordination with the two lower chambers (the ventricles) of the heart. It's unclear how sleep apnea might increase the risk of arrhythmias, but the increase in blood pressure may play a big role.
Coronary artery disease. Coronary artery disease is caused by the gradual buildup of fatty deposits in your coronary arteries (atherosclerosis). As the deposits (plaques) slowly narrow your coronary arteries, your heart muscle receives less blood. Eventually, diminished blood flow may cause chest pain (angina), shortness of breath or other symptoms. A complete blockage can cause a heart attack. Sleep apnea may increase your risk of coronary artery disease because of the swings in blood pressure that occur during sleep apnea. This, combined with dips in oxygen levels in your blood, might make your blood vessels more susceptible to damage.
Stroke. A stroke occurs when the blood supply to a part of your brain is interrupted or severely reduced, depriving brain tissue of oxygen and nutrients. Within a few minutes, brain cells begin to die. It's thought that damage and stress to your blood vessels, possibly caused by blood pressure and oxygen changes from sleep apnea, might make you more prone to a stroke.

Obesity, sleep apnea and heart disease: Is there a connection?

One reason Dr. Somers and other researchers are focused on sleep apnea and heart disease has to do with the increase in the number of obese and overweight individuals.

Being obese or overweight greatly increases the chances you'll develop sleep apnea. And while being overweight or obese has long been recognized as increasing your risk of heart disease, Dr. Somers wonders if the sleep apnea often caused by obesity might also play a role.

"We wonder how much of the obesity-related heart disease might be attributed to sleep apnea," he says.

What can you do?

Dr. Somers says right now he can't say for certain that treating sleep apnea will prevent heart disease. But because it's already known that sleep apnea can increase your risk of high blood pressure, his research is just one more reason for those with sleep apnea to seek treatment. He stresses that sleep apnea treatments have improved significantly in the last 10 years. So, if you've tried treating sleep apnea before and had no luck, try again.

Here are some of Dr. Somers' other suggestions:

Get evaluated for sleep apnea. Seek an evaluation from an accredited sleep center if your snoring is loud enough to disturb your sleep or that of others, you experience shortness of breath that wakes you up, you experience excessive daytime sleepiness, or your partner says that you stop breathing during sleep. If you have heart disease and any of the above apply to you, getting evaluated for sleep apnea may be especially important.
Try standard treatments. Sleeping on your side, weight loss and avoiding alcohol before bed are all proven steps you can take to reduce sleep apnea.
Consider continuous positive airway pressure (CPAP). If you have moderate to severe sleep apnea, you may benefit from a machine that delivers air pressure through a mask placed over your nose while you sleep. With CPAP (SEE-pap), the air pressure is increased just enough to keep your upper airway passages open, preventing apnea and snoring. Older types of CPAP devices were cumbersome, but the technology and user-friendliness have improved significantly. Sometimes dental devices that keep the jaw stable during sleep can help milder cases of sleep apnea.
Be vigilant if you have sleep apnea. You should carefully monitor your health, such as regularly checking your blood pressure if you have sleep apnea. Also, if you ever experience chest pain after waking up at night, get checked out.