Coronary Artery Disease and Heart Attack. Sleep apnea has been associated with heart disease regardless of the presence of high blood pressure or other heart risk factors. In a 2001 study, researchers observed that the more episodes of apnea and hypopnea a patient had, the higher the risk for a heart attack. Many of the factors associated with stroke and sleep apnea (a risk for blood clots and narrowing of the arteries) may also increase the risk for heart attacks. Obstructive sleep apnea, however, may have other effects that increase the risk for heart problems:
- Some evidence suggests that obstructive apneas cause an increase in stiffness and inflammation in the arteries, which is now proving to be an important aspect of heart disease, particularly in older adults.
- A 2002 study reported that the white blood cells of patients with apnea have an increased number of proteins called adhesion molecules on their surface that may bind to the lining of blood vessels and cause inflammation. Increasingly, scientists believe that inflammation plays an important role in the development of coronary artery disease, heart attacks, and many other major ailments.
Stroke. Sleep apnea doubles the risk for stroke. The worse the sleep apnea, the greater the risk; moderate-to-severe obstructive sleep apnea can triple the risk of stroke. Sleep apnea is also associated with high blood pressure, a known risk factor for stroke. However, people who have sleep apnea, but not high blood pressure, are also still at increased risk for stroke. Sleep apnea in stroke patients is also associated with a higher risk for worse symptoms after a stroke, including delirium, depression, poor response to speech, and difficulty conducting daily chores.
- A 2000 study observed that blood becomes more viscous (stickier) in the morning in people with obstructive sleep apnea compared to people without the sleep disorder. Such "sticky" blood is more apt to form clots that can lead to strokes. To support this, another 2000 study reported that stroke victims with sleep apnea tended to have higher levels of the blood protein fibrinogen than stroke victims without sleep apnea. Fibrinogen is a factor in blood that causes it to clot. Higher levels of fibrinogen have been linked to both strokes and heart attacks.
- A 1998 study reported that the carotid artery, the major artery to the brain, is in far greater danger of becoming sclerotic (hardened and narrower) in people with obstructive sleep apnea than in the average person. People with both diabetes and sleep apnea are at particularly high risk for this effect.
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