Sleep Apnea Chapter 6

Complications of the Heart & Mind


Cardiovascular Complications of Sleep Apnea

Sleep apnea that goes untreated can be lethal: people with sleep apnea have three times the risk of dying from any cause compared with people who don’t have sleep apnea. One of the more likely causes of death is cardiovascular disease, including heart attack and stroke, pulmonary vascular disease, congestive heart failure, and heart arrhythmias. READ MORE

  • Heart attacks. People with OSA are three to five times more likely to have ischemic heart disease, in which blood flow to the heart is reduced or stops altogether, producing a heart attack. OSA constricts arteries and contributes to atherosclerosis, or thickening and hardening of the arteries, which increases the risk of having a heart attack.

  • Stroke. OSA creates many conditions that make it more likely you will have a stroke. The walls of the carotid arteries—the main arteries carrying blood to your brain—can thicken, reducing blood flow. OSA damages blood vessels throughout your body, including your brain, and may make clotting more likely

  • Pulmonary vascular disease (disease of the blood vessels of the lungs). OSA and the hypertension it creates injure blood vessels throughout your body. Damage may be especially pronounced in the delicate vessels of your lungs. Pulmonary hypertension occurs in up to 53% of people with OSA

  • Congestive heart failure. Congestive heart failure and OSA often occur together. One study found that 50% of patients with left ventricular failure had OSA.

  • Arrythmias. Heart rhythm abnormalities, or arrhythmias, are commonly found in people with OSA. The arrhythmias most frequently found are tachy-brady syndrome, ventricular ectopy, and atrial fibrillation



What’s the Link between OSA and Cardiovascular Disease?

OSA is strongly associated with cardiovascular disease.

  • Hypoxemia may trigger systemic inflammation, as evidenced by the increased levels of C-reactive protein (a marker of inflammation) found in people with OSA.

  • Repeated hypoxemia and sleep deprivation may increase levels of cytokines (inflammatory components) in the blood and also increase numbers of adhesion molecules, making blood clots more likely to form.

  • Hypertension is a major culprit narrows large blood vessels and makes tiny capillaries more likely to break.



Sleep Apnea and Hypertension

There is a great deal of evidence that sleep apnea causes hypertension (high blood pressure). Some 50-60% of people with OSA have hypertension, and about 30% of people with hypertension are estimated to have OSA, often undiagnosed. Chronic hypertension is very dangerous and is a major risk factor for cardiovascular disease and stroke as well as kidney disease.

It seems likely that OSA creates hypertension by activating the sympathetic nervous system. which activates the “fight or flight” response. When it senses a threat, the sympathetic nervous system causes many physical reactions, including increased heart rate and raised blood pressure. READ MORE

Low Oxygen Levels
In this case, the “threat” that your sympathetic nervous system is reacting to is the hypoxemia, the low blood oxygen level created by sleep apnea episodes. Blood oxygen levels are measured as percentage of oxygen saturation. Normal oxygen saturation values are 97-99%. People with sleep apnea, though, may have oxygen saturation levels of 60% or even lower.

Your sympathetic nervous system reacts to hypoxemia by severely constricting your blood vessels and causing your heart to beat faster. This occurs at night and during the day. At night, when breathing resumes after stopping, blood pressure can surge as high as 250/110 mm Hg when blood is forced into severely constricted blood vessels.

Sympathetic activation continues into your waking hours, as well. Even when your blood oxygen and carbon dioxide levels are normal, sympathetic nervous system activity continues to constrict blood vessels and increase your heart rate. LESS


Sleepiness, Cognitive Problems, and Depression

If your normal sleep cycles are being disrupted every night, you’re obviously going to feel sleepy the next day. Sleep apnea has other serious consequences as well.

  • Drowsiness and fatigue can make it hard to work, to read or watch TV, and to get chores done. People with OSA may fall asleep at any time, for instance while eating a meal or even while driving a car—with sometimes deadly consequences.

  • Memory problems as well as difficulty concentrating and performing cognitive tasks (like math problems) have been linked to OSA. This may be due to the damaging effects of sleep apnea on the brain.

  • Social life and sexuality can suffer because of OSA. If you’re tired all the time, it’s hard to maintain relationships or to enjoy socializing. Because people with OSA often snore, partners may sleep in separate rooms, impairing intimacy. Men with OSA often suffer from erectile dysfunction.

  • Physical health can suffer because you’re too fatigued to exercise or play sports. Motor coordination may also be damaged by OSA.

  • Depression frequently accompanies OSA. In fact, people with depression are five times more likely to have a breathing-related sleep disorder than people who don’t have depression.



How Sleep Apnea Can Damage the Brain

Studies using magnetic resonance imaging (MRI) technology have shown that concentration of the brain’s gray matter—the cerebral cortex of the brain—is actually reduced in people with sleep apnea. Gray matter concentration was found to be decreased in areas involved in memory, concentration, cardiovascular activity, breathing, and executive functioning (which controls high-level brain functioning such as problem solving). READ MORE

The memory problems associated with OSA could be associated with damage to the hippocampus and the mammillary bodies. The hippocampus is required for the formation of long-term memories; it’s very sensitive to drops in oxygen level such as those that occur in sleep apnea. Also important to memory formation are the mammillary bodies, which are much smaller than normal in people with OSA. LESS


What Happens to the Brain in an Apnea Episode?

During an apnea episode, the brain’s blood vessels constrict, starving brain tissue of oxygen and causing brain cells to die. The process also promotes inflammation, further damaging delicate brain neurons.

The low levels of blood oxygen that result when breathing stops are very damaging to sensitive brain cells. But according to sleep expert Dr. Ronald Harper of UCLA, low levels of oxygen aren’t the only problem: the spikes of oxygen that occur when breathing resumes are also toxic to brain cells. Those oxygen spikes happen each time breathing ceases and then resumes.


Children and Sleep Apnea

The brains of children and adolescents are changing and developing very rapidly. Kids’ growth is regulated and promoted by intricate hormonal mechanisms that are coordinated by the brain. Some of these hormonal process take place only during sleep—for instance, growth hormone is released mostly during sleeping hours. READ MORE

Childhood sleep apnea is associated with these neuropsychological problems:

  • Failure to thrive

  • Problems concentrating

  • Behavioral problems

  • Developmental delay

  • Memory problems

  • Learning difficulties

