How Sleep Apnea Can Cause a Stroke

Posted by Admin on March 9, 2010
Obstructive sleep apnea decreases blood flow to the brain and causes changes in the brain that increase sufferers' risk of suffering from a stroke or dying in their sleep, according to a study published by The American Physiological Society. The decreased blood flow to the brain causes elevated blood pressure within the brain that eventually harms the brain's ability to modulate these changes and prevent damage to itself.

Sleep apnea is the most commonly diagnosed disorder amongst sleep-related breathing conditions and can lead to debilitating and sometimes fatal consequences. This study identifies the mechanism behind stroke in sleep apnea patients. When sleep apnea occurs, the upper airway becomes blocked, which hinders or stops breathing and reduces the flow of oxygen and raises blood pressure. The person eventually awakens and resumes breathing, restoring normal blood oxygen and blood flow to the brain.

Normally, the brain regulates its blood flow to meet its own metabolic requirements, even despite changes in blood pressure – process known as cerebral autoregulation. The study found the sudden changes in blood pressure and blood flow during apnea episodes each night reduces the brain’s ability to regulate these functions.

To understand the process that enables sleep apnea to be a risk factor for death and stroke, researchers monitored patients with severe sleep apnea who experienced more than 30 episodes an hour during sleep. The researchers observed changes in the participants’ blood pressure while standing and squatting. Standing from a squatting position lowers blood pressure as can be experienced during normal daily activity. They also monitored the participants as they slept. The study found that the sleep apnea group:

  • had reduced cerebral blood flow velocity
  • had significantly lower blood oxygen levels during sleep
  • took longer to recover from a drop in blood pressure
  • took longer to normalize blood flow to the brain

The findings indicate that repeated changes in blood pressure and low oxygen levels eventually impair the body’s ability to regulate blood flow to the brain. Sleep apnea may occur over a long period of time before a person becomes aware of it and seeks medical treatment. Here are the main symptoms to watch out for:

  • After eight hours of sleep, you don’t feel rested. During the day, you become increasingly drowsy and by the afternoon, you want to nap.
  • During the night, your loud and habitual snoring disturbs others
  • A person sleeping near you may observe pauses in your breathing during sleep.


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