Sleep apnea and stroke: the risk, the research and the warning signs

Sleep apnea is linked with a higher risk of stroke, and it's found in most people who have already had one. Large studies show the link holds even after accounting for high blood pressure. What's less clear is whether treating sleep apnea prevents strokes: the biggest trial, SAVE, didn't show that, though people in it used CPAP for only about three hours a night. If you ever notice stroke symptoms in yourself or someone else, call 911 straight away.

Is sleep apnea a risk factor for stroke?

Sleep apnea is a risk factor for stroke according to several large studies. The NHLBI says sleep apnea can cause low oxygen levels during sleep, and that the effort of restarting breathing many times a night can damage organs and blood vessels. It lists stroke among the conditions sleep apnea may raise the risk of, along with atrial fibrillation, heart attack and hard-to-control high blood pressure.

A 2005 study in the New England Journal of Medicine followed 1,022 patients who had sleep studies, 697 of whom had obstructive sleep apnea. Sleep apnea was linked with a higher risk of stroke or death from any cause. After adjusting for age, sex, race, smoking, alcohol, body mass index, diabetes, high cholesterol, atrial fibrillation and high blood pressure, the risk was still nearly double. The more severe the sleep apnea at the start, the higher the risk.

The Sleep Heart Health Study, published in 2010, looked at a general community sample. It followed 5,422 adults with no history of stroke and no sleep apnea treatment for a median of 8.7 years, during which 193 had an ischemic stroke, the kind caused by a blocked blood vessel.

• In men, stroke risk rose steadily with sleep apnea severity. Men in the highest quarter, with an obstructive apnea-hypopnea index above 19, had 2.86 times the risk of those in the lowest.
• In the mild to moderate range, each one-point increase in the index raised men's stroke risk by about 6%.
• In women, the link wasn't significant across quarters, but risk rose at an index above 25.

These are observational studies, so they show a strong link rather than proof of cause. For context, MedlinePlus says about 80% of strokes are ischemic, caused by a blood clot that blocks a blood vessel in the brain, and that high blood pressure is the primary risk factor for stroke. High blood pressure is part of the story, and our guide to sleep apnea and high blood pressure covers it. Atrial fibrillation is another: MedlinePlus notes that atrial fibrillation and other heart diseases can cause blood clots that lead to stroke, and our article on sleep apnea and atrial fibrillation explains how the two are linked.

How common is sleep apnea after a stroke?

Sleep apnea is very common after a stroke. A 2019 meta-analysis in Neurology pooled 89 studies with 7,096 people who'd had a stroke or a transient ischemic attack (TIA), a short-lived blockage sometimes called a mini-stroke. All had formal sleep testing.

Sleep-disordered breathing, with an apnea-hypopnea index above 5, showed up in 71% of them. Severe sleep apnea, with an index above 30, showed up in 30%. The rates were similar whether people were tested in the first month after their stroke, at one to three months, or later, which suggests it doesn't simply fade as people recover.

The American Heart Association's 2021 scientific statement on sleep apnea and heart disease gives a similar picture, saying sleep apnea affects as many as 40% to 80% of people with stroke and several heart conditions. It also says sleep apnea is often underrecognized and undertreated in heart care.

Does treating sleep apnea lower stroke risk?

Treating sleep apnea hasn't been proven to lower stroke risk in a large trial, though regular CPAP use may matter. The key study is the SAVE trial, published in the New England Journal of Medicine in 2016. It's worth being precise about what it tested and found.

SAVE enrolled 2,717 adults aged 45 to 75 who had moderate to severe obstructive sleep apnea and existing coronary or cerebrovascular disease, meaning heart disease or a previous stroke or TIA. Most were men with little daytime sleepiness. After a one-week trial run on a sham machine, they were randomly assigned to CPAP plus usual care or usual care alone. Because stroke was one of the outcomes and people could join because of existing cerebrovascular disease, SAVE is an important test of whether CPAP can prevent strokes in people with sleep apnea.

So SAVE found that CPAP, as people actually used it, didn't prevent strokes or other cardiovascular events over an average of 3.7 years. It did make people feel better. The main limitation is how little CPAP was used.

That's why a 2023 analysis in JAMA is worth knowing about. It combined individual data from 4,186 people in three trials, SAVE, ISAACC and RICCADSA, all in people with heart or blood vessel disease and sleep apnea. Overall, CPAP and usual care had similar rates of repeat major heart and stroke events. But in an analysis of people who used CPAP at least 4 hours a day, good use was linked with a lower risk, with a hazard ratio of 0.69. That type of analysis can't fully rule out that people who stick with treatment differ in other ways. Still, it's a strong reason to make CPAP comfortable enough to use all night.

Does CPAP help after a stroke?

CPAP may help recovery after a stroke, based on pooled smaller trials. A 2026 meta-analysis in Sleep Medicine Reviews combined 21 randomized trials with 1,457 people who'd had a stroke. Positive airway pressure treatment was linked with fewer repeat vascular events, better recovery from neurological deficits, less daytime sleepiness, lower depression scores and better thinking skills. It didn't improve independence in everyday activities.

Those results are encouraging, but they come from many small trials rather than one large one. The AHA's 2021 statement says there is clinical equipoise, meaning genuine uncertainty among experts, about screening for and treating sleep apnea after a stroke. In practice, that means the decision is made person by person with your care team.

If CPAP is hard to manage, the NHLBI suggests telling your provider if your mask doesn't fit or stay on, so they can try a different mask, machine or settings. Our guides to getting used to CPAP and sleep apnea treatment options may help.

What are the warning signs of a stroke?

The warning signs of a stroke are easiest to remember with FAST. MedlinePlus describes it like this:

• Face: drooping on one side when smiling
• Arm: weakness, so one arm drifts downward when both are raised
• Speech: slurred or strange
• Time: time to call 911

MedlinePlus lists other sudden symptoms too: numbness or weakness of the face, arm or leg, especially on one side; confusion or trouble speaking or understanding; trouble seeing in one or both eyes; trouble walking, dizziness or loss of balance; and a sudden severe headache with no known cause. It says to call 911 right away, because every minute counts.

Don't wait to see if symptoms pass. The NHS says stroke symptoms can sometimes stop after a short time, and you should still get medical help straight away, including if you've had signs of a stroke in the last 24 hours that have now gone. MedlinePlus notes that a TIA puts you at much higher risk of a stroke. The NHS also says not to drive yourself to the emergency department.

Who should get checked for sleep apnea?

Anyone with signs of sleep apnea should get checked, and that matters even more if you've had a stroke, TIA or heart disease. Our guide to sleep apnea warning signs explains what to look for, and what happens at a sleep study walks through testing.

If you've already had a stroke and are wondering about sleep apnea, ask your stroke team or doctor whether a sleep test makes sense for you. If you're pregnant and have new loud snoring or breathing pauses, tell your clinician.

If you're diagnosed and start treatment, the NHLBI advises using your PAP machine for all sleep, including naps, and having regular checkups to make sure treatment is working. Our article on whether sleep apnea is deadly looks at the long-term outlook, and sleep apnea and the heart covers the wider cardiovascular picture.

This article is general information, not medical advice. If you think someone is having a stroke, call 911 now.

Read next

• What sleep apnea does to your heart
• Sleep apnea and atrial fibrillation
• Is sleep apnea deadly?

* This content is for informational and educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease or health condition. Talk to a qualified healthcare provider about your health.