When you have sleep apnea, a condition that causes sleep-disordered breathing, your body and brain receive less oxygen at night while sleeping. This can increase your risk for health complications like stroke. In fact, if you have sleep apnea, you’re two to four times more likely to have a stroke.

Obstructive sleep apnea (OSA), the most common type of sleep apnea, is largely responsible for strokes in people with sleep apnea. It can also increase your risk of experiencing another stroke, especially if your condition isn’t treated. Central sleep apnea (CSA), another form of sleep apnea, can also cause a stroke, though it’s not as common.

Here’s what you need to know about the connection between sleep apnea and stroke, and why having OSA or another type of sleep apnea may increase your risk of stroke.

Why Does Sleep Apnea Increase Stroke Risk?

While more research is needed to fully understand how sleep apnea increases stroke risk, there are a number of different factors that could be increasing your risk.

When you have sleep apnea, your oxygen levels drop and your blood pressure goes up when you’re asleep. The more often this happens, the more likely you are to develop inflammation and damage to the lining of your blood vessels. Drops in oxygen and increased blood pressure can also affect how your blood vessels widen or narrow, increasing your risk of blocked arteries and blood clots — two factors that often lead to stroke.

During sleep apnea, your airway may also be blocked, or your breathing may stop. When this happens, it puts extra strain on your heart, eventually leading to a change in your heart’s structure or shape. Regularly experiencing hypoxia (when your body doesn’t get enough oxygen) puts stress on your heart and impacts the blood pressure inside your chest, particularly between your heart and lungs.

Hypoxia can cause your heart to become thicker and affect how efficiently it pumps blood to the rest of your body. It can also lead to cardiovascular diseases. And because sleep apnea reduces the amount of oxygen your heart is getting, it also increases your risk of an irregular heartbeat or atrial fibrillation, a condition that increases your risk of a stroke.

Types of Stroke People May Experience With Sleep Apnea

There are a few types of strokes most likely to occur in people with sleep apnea. These include:

• Transient ischemic attack (TIA) — Often referred to as a mini stroke, a TIA is a temporary blockage with symptoms that go away. Having this type of stroke is usually a warning that a more serious stroke could occur.
• Ischemic stroke — This type of stroke is more serious and occurs when blood flow to your brain is blocked. An ischemic stroke can cause a disability, brain damage, and even death.
• Wake-up stroke (WUS) — This stroke is an ischemic stroke that occurs when you’re sleeping and is strongly linked to sleep apnea. Wake-up stroke means that people go to bed without any symptoms and wake up in the morning experiencing neurological issues.

Is Stroke Risk Greater With More Severe Sleep Apnea?

The severity of sleep apnea is measured during a sleep study by calculating the apnea-hypopnea index (AHI). This measurement is determined by taking an average of how many breathing pauses (apneas) and how many shallow breaths (hypopneas) you experience during one hour of sleep.

If you have 15 to 30 incidents in one hour, or an AHI score of 15 to 30, you have moderate sleep apnea; and if you have 30 or more, you have severe sleep apnea. The more severe your AHI score, the more likely you are to experience a stroke, especially if you’re older.

Researchers have found that having an AHI greater than five nearly doubles your risk of stroke or death compared with someone without the condition. And if your AHI score is 30 or higher, your risk of stroke becomes two and a half times greater.

Men with sleep apnea are at greater risk for a stroke than women. Men with an AHI greater than 20 had nearly three times greater risk for a stroke than those with an AHI less than five. A woman’s risk for stroke increased when her AHI was greater than 25.

Does Sleep Apnea Develop After a Stroke?

After having a stroke, you may be more likely to develop sleep apnea if you didn’t already have it. Most of the time, you will develop OSA rather than CSA after a stroke, though either can occur.

About 30 percent to 70 percent of people develop OSA after a stroke, while between 6 percent and 24 percent of people develop CSA. For those who develop CSA, this can be directly related to having a stroke and can sometimes improve a few months into recovery. However, OSA influences stroke in both directions. Having OSA is a risk factor for having a stroke and, in other instances, it can develop after a person has had a stroke.

Continuous positive airway pressure, or CPAP, is the preferred way to treat sleep apnea, but it’s not always tolerated by someone who has had a stroke. They may have issues putting the mask on or wearing the mask because of their symptoms. In these cases, healthcare providers sometimes look for other treatment options.

How Sleep Apnea Treatments Influence Stroke Risk

Even though sleep apnea is an extremely common condition, many people have the condition and don’t know it. Experts estimate that 90 percent of cases go undiagnosed. In some instances, people are aware that they have the condition but aren’t being treated.

Untreated sleep apnea can have major impacts on your health. Research shows that treating OSA with CPAP can reduce the risk of stroke and improve your outcome if you’ve already had a stroke. In fact, one study found that using CPAP at night can lower the risk of a stroke, heart attack, and even death by around 17 percent in people with severe OSA.

Using a CPAP machine on a regular basis can also improve neurological symptoms after a stroke. And, CPAP use can improve cognitive abilities and your overall quality of life.

Talk to Your Doctor

If you have sleep apnea and are concerned about your risk for stroke or other health complications, talk to your doctor. They can help you understand how you can best treat your sleep apnea and avoid developing other health problems.

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On MySleepApneaTeam, people share their experiences with sleep apnea, get advice, and find support from others who understand.

If you have been diagnosed with sleep apnea, what is one thing you’ve done to reduce your stroke risk that has been most beneficial? Let others know in the comments below.