Because they happen in your sleep, sleep strokes can delay lifesaving treatment. This can make them more serious than other types of stroke.

A stroke happens when a blocked artery prevents blood from flowing to the brain, or a blood vessel in the brain leaks or ruptures. When a stroke happens while you’re sleeping, it’s known as a “wake-up stroke.”

Ahead, we’ll discuss what you need to know about sleep strokes, including what causes them, how to recognize them, and more.

A wake-up stroke occurs when you go to sleep healthy, without any signs of a stroke, and wake up with stroke symptoms. When someone has a wake-up stroke, it’s difficult to know exactly when the stroke happened ― just that it happened during sleep.

Statistics suggest that roughly 20% of all acute ischemic strokes are wake-up strokes, but researchers still aren’t entirely sure what causes sleep strokes.

One article from 2017 explored the available research on the cause, development, and clinical features of wake-up strokes. According to the authors, they narrowed down two factors that might contribute to the risk of having a sleep stroke:

  1. Time of day: Studies have shown that there’s a higher risk of having a stroke during the early hours of the day, especially during the period from 6 a.m to noon.
  2. Health conditions: Research suggests that conditions like atrial fibrillation and obstructive sleep apnea may increase the risk of having a sleep stroke.

Other than these risk factors, wake-up strokes don’t actually appear to be clinically different than strokes that happen while someone is awake.

However, because wake-up strokes happen during sleep, people aren’t usually able to get medical help quickly. Without prompt treatment, an untreated stroke can continue to damage the brain and increase the risk of death.

Is it rare to have a stroke in your sleep?

Having a stroke in your sleep might not be as rare as you think. In fact, several studies have found that wake-up strokes may account for upward of a quarter of all stroke cases ― if not more.

A study from 2019 explored the relationship between obstructive sleep apnea and stroke outcomes in people who had both wake-up and non-wake-up strokes. In this study, wake-up strokes accounted for roughly 1/3 of all included stroke cases.

In another larger study from 2022, researchers analyzed the prevalence of wake-up strokes and unknown-onset strokes in over 60,300 patients. Results of the study showed that roughly 19% were wake-up strokes ― with another 18.4% having no known time of onset.

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When someone has a stroke in their sleep, the neurological symptoms of a stroke appear after waking up. Some of these immediate symptoms may include:

Another way to tell if someone might have had a stroke is by using the “FAST” method. FAST refers to the symptoms of face drooping, arm weakness, speech difficulty, and the emphasis on “time” or getting help as quickly as possible.

Some risk factors for stroke, like genetics, age, and gender, are outside of our control. However, there are a handful of ways that you can reduce your risk of having a stroke.

One of the biggest ways to lower your stroke risk is by limiting potentially harmful lifestyle behaviors. For example, if you smoke cigarettes or drink more than a low to moderate amount of alcohol each day, addressing these behaviors can lower your risk.

Another way to reduce the risk of a stroke is by getting proper treatment for other health conditions that can increase your stroke risk. Some of these conditions include high blood pressure, high cholesterol, diabetes, and atrial fibrillation.

Finally, you can make sure to give your heart the support it needs by moving your body regularly, eating plenty of nourishing foods, and getting enough sleep.

A sleep stroke, known as a wake-up stroke, describes a type of stroke that happens while someone is sleeping. According to studies, around 20% of all ischemic strokes are wake-up strokes ― although this figure may be even higher.

If you or someone close to you has shown the symptoms of a stroke, especially right after waking up, it’s important to get help or call 911 as quickly as possible.