Can Sleep Apnea Increase the Risk of a Stroke?

Stroke is one of the leading causes of long-term disability and death globally. Many conditions have long been known to increase the risk of stroke, like a high level of blood cholesterol, diabetes, high-blood pressure, smoking, and atrial fibrillation. However, now snoring, or rather sleep apnea, has been added to this list. Sleep apnea is also now considered as an independent risk factor as it increases the risk of stroke even in those with no other visible causes. 

It is vital to know the various health complications that sleep apnea can cause if not treated, especially since many of the complications can be prevented. Apart from a stroke, if not treated, sleep apnea can cause high blood pressure, cardiac arrest, atrial fibrillation, car and work accidents, and type 2 diabetes.

So how intense is this relationship between stroke and sleep apnea?

Measuring the severity of sleep apnea is not an easy task, as it is not a condition that occurs during the day while visiting a doctor. Many of the symptoms are present at night and at home, while you are sleeping. So, in many cases, someone with sleep apnea may not even be aware of it. The most common symptom of sleep apnea is snoring, which can often be identified by a partner, if they have one. Other than that, a patient can experience chronic fatigue, sleepiness throughout the day, and headache, but more often than not, these symptoms are brushed aside.

The most trusted and accurate way to diagnose sleep apnea is the use of a polysomnography, which gives the best results if done in a clinic rather than at home (however, these tests are made available if the patient chooses to do it at home). It is not a very comfortable procedure, as a person needs to sleep in a lab while wearing various sensors to measure their respiration, heart rate, and other critical parameters.

Studying the relationship between a stroke and snoring is not an easy task, considering that a stroke is an acute condition. A stroke is not something that produces particular symptoms days or months before it occurs. Though snoring is a far more common and chronic condition, it may exist for years without causing much harm. Although as many as one-third adults snore now or then, a sleep disorder is only in about 4-7% of that population.

Thus, to clearly understand the relationship between the two conditions, researchers checked the prevalence of sleep apnea in patients who had a stroke just some time back. During the study, they found that 77% patients who had a stroke also had symptoms of sleep apnea. This was much higher than an average of less than 5% in the general population. Further, they noticed that those with sleep apnea were more likely to die after a stroke. 

Why does snoring increase the risk of stroke?

The reasons could be many, like hypoxia, the slowdown of the regenerative process due to disturbances in sleep, increase in inflammatory conditions, hormonal imbalances to name a few. We know quite well that while we're sleeping there is a slow down of most our body's activities due to the dominance of the parasympathetic nervous system. There is also a slowdown in respiration and heart rate. If a person has woken up too often due to snoring and sleep apnea, this nighttime rhythm is disturbed, changing the balance in favor of the sympathetic nervous system. This means that there is more stress on the hear, which also increases the risk of vascular conditions.

Hypoxia, caused by sleep apnea, would cause vasoconstriction and increased the load on the heart while sleeping, which also adds to the risk. Further, it is proposed that snoring over an extended period may cause vibration trauma to the carotid artery, which is vital with supplying blood to the brain. It seems that these disturbances of hemodynamics can be a result of a combination of factors that can keep repeating themselves night after night, finally leading to the elevated risk of embolism and stroke.

Hence, we need to understand that snoring can be the earliest sign of sleep apnea and stroke, even though it still remains as one of the least appreciated and recognized risk factors for stroke. However, to decrease the risk of stroke, controlling hypertension, metabolic disturbances, high cholesterol may not be enough. You may need to know treat both snoring and sleep apnea aggressively after a proper diagnosis. If a person knows that they are snoring or if their partner has pointed it out to them, then it would make sense to consult a sleep specialist. If required, it may not be a bad idea to undergo polysomnography in order to confirm the diagnosis. Though there are various treatment modalities for snoring, the most effective treatment is the CPAP machine.

Concluding thoughts

In the words of Mark Twain, “Jim begun to snore--soft and blubbery at first, then a long rasp, then a stronger one, then a half a dozen horrible ones like the last water sucking down the plug-hole of a bath-tub, then the same with more power to it, and some big coughs and snorts flung in, the way a cow does that is choking to death.” When writing this, Mark Twain knew very little about snoring, as it not only creates the most unpleasant of sounds, it also can be a dangerous symptom of something larger.

Snoring has long remain a subject of jokes and laughter, but researchers are uncovering the amount of diseases and conditions that snoring is connected to. It's definitely not a laughing matter and definitely should not be ignored. 

References

1. Yaggi HK, Concato J, Kernan WN, Lichtman JH, Brass LM, Mohsenin V. Obstructive Sleep Apnea as a Risk Factor for Stroke and Death. N Engl J Med. 2005;353(19):2034-2041. doi:10.1056/NEJMoa043104.

2. Dyken ME, Somers VK, Yamada T, Ren Z-Y, Zimmerman MB. Investigating the Relationship Between Stroke and Obstructive Sleep Apnea.Stroke. 1996;27(3):401-407. doi:10.1161/01.STR.27.3.401.

3. Sharma S, Culebras A. Sleep apnoea and stroke. Stroke Vasc Neurol. November 2016:e000038. doi:10.1136/svn-2016-000038.

4. Davis AP, Billings ME, Longstreth WT, Khot SP. Early diagnosis and treatment of obstructive sleep apnea after stroke. Neurol Clin Pract. 2013;3(3):192-201. doi:10.1212/CPJ.0b013e318296f274.