For the estimated 25 million people in the U.S. who suffer from sleep apnea, poor sleep is a nightly occurrence. While the fogginess, headache, and daytime fatigue that follows a restless night is to be expected, there are other serious health risks that can accompany sleep apnea, especially if left untreated. Sleep apnea and high blood pressure are one of the most common links, affecting all systems of the body (including the heart). Here’s what you should know.

What does sleep apnea do to your heart?

Sleep apnea puts incredible stress on the body, depriving it of oxygen for ten to 20 seconds at a time, as many as 20 times an hour, all night long.

When the brain is deprived of oxygen, the blood vessels respond dramatically.

  • Blood vessels constrict: This increases the flow of oxygen to the brain and heart
  • Blood pressure increases: The body needs more oxygen, and the increased blood pressure helps to supply it

If these two things occurred only during apneic episodes when breathing stopped, then the body might have few lasting effects. But the body does not stop reacting in this way when the sleeper wakes. The extra adrenaline released during the night to stimulate breathing continues to be released during the day. This adrenaline continues to affect how the heart works.

The cardiovascular system remembers oxidative stress during the day and overcompensates. As a result, inflammation in the body increases (measured by the presence of a C-reactive protein), heart rate increases, and atrial walls thicken. Because of this, people with sleep apnea have increased rates of atrial fibrillation and heart failure.

Whether sleepers have obstructive sleep apnea, central sleep apnea, or complex sleep apnea, these symptoms are taxing to the body. Sleep apnea and blood pressure are closely linked, and this can affect the function of your heart.

Can sleep apnea cause high blood pressure?

The link between sleep apnea and high blood pressure plays out in the heart but also stands on its own as a dangerous complication.

When we sleep, our blood pressure usually drops between ten and 20% of its daytime rate. Not so for those who suffer from sleep apnea. The stress that occurs when the body is repeatedly deprived of oxygen at night causes blood pressure to rise by as much as 20% every night. Just like the heart remembers the oxidative stress, so too, does the blood pressure. Even just one apneic episode makes it harder for the body to regulate blood pressure.

An estimated 30 to 50% of people with high blood pressure also have sleep apnea. Sleep apnea is most common in patients with resistant hypertension that has not responded to treatments.

Glen Foster, an assistant professor of health and exercise science and researcher on a study that further proved sleep apnea’s effects on all of the body’s systems, noted that:

“…[Our] study shows this condition has an impact on the cardiovascular system that can begin within a single day. After just six hours of fluctuating oxygen levels, similar to what happens with sleep apnea, the body’s ability to regulate blood pressure is impaired. These changes occurred almost immediately in healthy young adults who were not experiencing the cumulative effects years of sleep apnea could bring about.”

In other words, sleep apnea and hypertension are linked from the very first night of poor sleep.

Even if the sleeper escapes the damaging effects of one night of sleep apnea, sleep apnea and high blood pressure are still likely. This may be related to the increased production of endothelin, a substance that causes the blood vessels to constrict. Over time, this increased production can damage blood vessels, resulting in hypertension and even stroke.

Hypertension does, in many cases, lead to stroke, and patients with sleep apnea have