Silent Stroke and Sleep Apnea

The news that sleep apnea is a risk factor for stroke isn't new. We've known for some time that sleep apnea is associated with elevated risk of stroke. But this new research shows just how common sleep apnea is among stroke sufferers.
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Here is yet another health risk associated with sleep apnea: stroke. The news that sleep apnea is a risk factor for stroke isn't new. We've known for some time that sleep apnea is associated with elevated risk of stroke. But this new research shows just how common sleep apnea is among stroke sufferers. In particular, these results reveal how frequently sleep apnea is present in patients who suffer silent strokes.

What is a silent stroke?

  • Silent strokes have no visible or outwardly identifiable symptoms.
  • In most cases, people who suffer a silent stroke don't even know they've had a stroke.
  • Silent strokes are referred to as "silent" because they do not present the outward physical symptoms that are typically associated with stroke, including slurred speech, paralysis and severe pain.
  • Silent strokes are a serious health concern, however -- they cause permanent damage to the brain, most often in the regions of the brain that govern mood, thought, cognition and memory.
  • Silent strokes are themselves a risk factor for other types of stroke, including major stroke.

Researchers from the University of Alabama, Birmingham and from Germany's University of Technology Dresden teamed up to investigate the frequency and severity of obstructive sleep apnea as risk factors for silent stroke. The results of their research revealed high rates of sleep apnea among patients with silent stroke. Over a period of 18 months, researchers evaluated 56 people who had been identified as having suffered acute cerebral ischemia, a type of stoke that interrupts the flow of blood to the brain. Within five days of stroke symptoms, patients were evaluated using MRI and CT scan to identify specific details of stroke effects in the brain, and were also assessed for the presence and severity of sleep apnea. Researchers found:

  • Sleep apnea was present in 51 of 56 stroke patients evaluated -- that's 91 percent.
  • Of these 51 patients, 29 percent had severe sleep apnea and 30 percent had moderate sleep apnea.
  • Severe sleep apnea was present in 58 percent of patients who had suffered a "clinically silent infarct," commonly known as a silent stroke
  • Severe sleep apnea was present in 38 percent of patients with chronic microvascular changes -- these are tiny lesions to white matter in the brain that are associated with silent stroke.
  • Sleep apnea -- and the degree of its severity -- was found to be a strong predictor for silent stroke.
  • Patients with severe sleep apnea progressed more slowly and less successfully in the early stages of recovery than those patients without sleep apnea.

What we don't know from these results is whether sleep apnea is a factor in causing stroke, or whether people who suffer strokes are then more likely to develop sleep apnea. When a person suffers from sleep apnea, their airway collapses during sleep. This airway collapse temporarily cuts off breathing and diminishes the levels of oxygen in the bloodstream. People who suffer from moderate to severe sleep apnea have episodes of disrupted breathing dozens, even hundreds, of times per night. (In this most recent study, researchers defined severe sleep apnea as 30 or more episodes of disrupted breathing per hour of sleep.) Learning more about how disordered breathing affects the brain and may contribute to stroke risk is a critical avenue for additional research.

We do know this: sleep apnea is associated with elevated risk for a range of serious and chronic illnesses. Obstructive sleep apnea has been linked to:

1.Cardiovascular problems. In addition to being a risk factor for stroke, sleep apnea is also associated with hypertension, heart disease and heart failure. This study found that obstructive sleep apnea increased a person's risk of heart attack by 30 percent over a four- to five-year period.

2.Diabetes. There's increasing evidence of a link between diabetes and sleep apnea. This study found high rates of obstructive sleep apnea among men with Type 2 diabetes. Even worse news: Most of these sleep apnea cases were undiagnosed before the study.

3.Sexual dysfunction. Sleep apnea has been shown to cause sexual problems in both men and women. This study showed women with sleep apnea had significantly higher rates of sexual problems, both with sexual performance and satisfaction. This research revealed that men with erectile dysfunction were more than twice as likely to also suffer from obstructive sleep apnea.

We've got a great deal more to learn about how sleep apnea may contribute to these conditions, as well as to its role as a risk factor for stroke. What's already clear is that sleep apnea is a red flag for stroke and other serious health problems. Screening for sleep apnea -- and assessing sleep health in general -- needs to be part of the diagnostic and risk assessment process for patients. If sleep apnea and other sleep disorders are ignored, we ignore an opportunity to identify at-risk patients before the worst occurs.

Sweet Dreams,

Michael J. Breus, PhD
The Sleep Doctor™

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