Sleep Apnea and Heart Disease
Treatment can reduce cardiovascular risk
People who snort, snore and gasp their way through the night with untreated sleep apnea may risk more than waking up tired, irritable or with a headache.
They also may be hurting their heart.
“In the last two decades, there has been significant evidence showing a very strong connection between sleep apnea and heart disease,” says board-certified sleep specialist and pulmonologist Akshay Mahadevia, M.D. “If you have untreated sleep apnea, it will continue to make the progression of your cardiovascular disease worse. Treating sleep apnea has a very beneficial effect.”
Dr. Mahadevia spoke recently at the first in a series of sleep seminars this year hosted by the Genesis Sleep Disorders Center.
Obstructive sleep apnea, the most common type, occurs when muscles in the back of the throat relax and momentarily close off the airways. The blood oxygen lowers. The brain senses this decrease and briefly rouses the person from sleep so the airways reopen. This pattern can repeat itself 10 times or more each hour all night.
That combination of disturbed sleep and lack of oxygen leads to serious cardiovascular complications like high blood pressure, coronary artery disease, congestive heart failure, stroke and abnormal heart rhythms.
When a person has sleep apnea, several changes in the body occur that directly affect the cardiovascular system.
• Sympathetic activation -- Sleep apnea revs up the sympathetic nervous system, causing it to release more adrenalin and epinephrine than usual. This stresses the cardiovascular system, increasing heart rate and blood pressure.
• Endothelial dysfunction -- Decreases in oxygen damage the endothelial lining in the blood vessels, causing them to constrict and fail to dilate. “The lining of the blood vessel becomes damaged and broken down, causing the cholesterol and fatty substances to sit there on the endothelium and leading to the plaque formation of coronary artery disease,” Dr. Mahadevia says.
• Inflammation -- Lack of oxygen due to sleep apnea releases inflammatory chemicals in the body. Among the chemicals is C-reactive protein, which causes inflammation in the blood vessels. “If you have high C-reactive protein, you’re more likely to have coronary artery disease,” Dr. Mahadevia says.
• Oxidative Stress --Nocturnal drops in oxygen during sleep increase the release of superoxides from the blood cells, which is damaging to the cardiovascular system. That level is reduced with continuous positive airway pressure.
• Metabolic -- Metabolic syndrome is a cluster of conditions — increased blood pressure, a high blood sugar level, excess body fat around the waist or abnormal cholesterol levels — that occur together, increasing the risk of heart disease, stroke and diabetes. Studies show that people with sleep apnea have abnormal metabolic markers that cause obesity and insulin resistance. Patients with sleep apnea also have high levels of leptin, which has been associated with weight gain.
• Changes in intrathoracic pressure -- Upper airway obstruction due to sleep apnea affects the mechanics of the heart. The chest struggles to expand to open up the airway. This causes negative pressure inside the chest and affects the cardiovascular system.
In addition, obstructive sleep apnea may make nighttime heart attacks more likely than daytime heart attacks, studies show. “It’s very clear that sleep apnea can cause sudden cardiac death during sleep,” Dr. Mahadevia says. “Fortunately, we don’t see this very often.”
Obstructive sleep apnea also has a link to high blood pressure, stroke, atrial fibrillation and heart failure.
Treating obstructive sleep apnea improves high blood pressure, and thus, reduces the risk of stroke. “There’s very clear evidence that obstructive sleep apnea can cause high blood pressure,” Dr. Mahadevia says. “Once we treat patients with sleep apnea, over a period of time their blood pressure continues to improve. They either go off their blood pressure medication or are able to reduce it.”
Many people with atrial fibrillation also have sleep apnea. Treating sleep apnea can reduce the occurrence of atrial fibrillation by as much as 50 percent, studies show.
Heart failure is a chronic, progressive condition in which the muscle is unable to pump enough blood to meet the body’s needs for blood and oxygen. “Every night you don’t get enough oxygen due to sleep apnea causes the cardiac muscle to get weaker and weaker,” Dr. Mahadevia says. “That’s why patients with obstructive sleep apnea often have a low ejection fraction, which is the ability of the heart muscle to squeeze and eject blood. If you treat sleep apnea and correct the oxygen problem, the ejection fraction improves.”
About 40 percent of people with congestive heart failure also have a sleep-related breathing disorder called central sleep apnea. In central sleep apnea, there also are repetitive episodes of interruptions in breathing during sleep. The difference is that the breathing passage remains open but the person stops making efforts to breathe. “Central sleep apnea in heart failure patients is a bad prognostic sign,” Dr. Mahadevia says. “By treating the sleep disorder, we can improve their prognosis and mortality.”
The earlier in life sleep apnea is diagnosed and treated, the better a person’s heart health will be later in life.
“If we can detect sleep apnea in a 30-year-old man, treat him and improve his lifestyle, we can prevent him from having high blood pressure, high cholesterol and can decrease his chances of developing certain cardiovascular diseases,” Dr. Mahadevia concludes.