Our understanding of the relationship between obstructive sleep apnea and stroke is growing more complicated. Sleep apnea is a well-established risk factor for stroke. Research offers compelling evidence that sleep disordered breathing, including obstructive sleep apnea, elevates the risk for stroke as well as for heart disease and high blood pressure, which themselves make people more vulnerable to stroke.
Sleep apnea occurs when the muscles of the airway collapse, blocking normal breathing during sleep. Sleep apnea diminishes and alters the flow of blood and oxygen to the brain. It also increases blood pressure and fluid pressure in the brain.
New research indicates that people who experience a particular form of injury to the brain as a result of stroke are more likely to have obstructive sleep apnea. Scientists recently presented findings of a study exploring the link between location of stroke-related brain injury and occurrence of sleep apnea at the American Stroke Association’s International Stroke Conference.
Researchers investigated how often sleep apnea is present among people whose stroke resulted in injury to the lower part of the brain called the brain stem compared with strokes that didn’t involve the brain stem. The brain stem is a small but critical area located at the back and base of the brain, close to the spinal cord. The brain stem helps control many essential body functions, including breathing and swallowing and heart rate. This area of the brain is also involved in regulating the sleep cycle.
The study included 355 people who’d recently suffered an ischemic stroke, a form of stroke caused by blockage of blood vessels supplying blood to the brain. The study participants were recruited from the BASIC Project, an ongoing study of stroke that focuses primarily on Mexican-Americans. Hispanic adults made up 59% of the study group.
Researchers used brain scans to identify whether individuals had experienced injury to the brain stem as a result of their stroke. Participants were evaluated for sleep apnea using respiratory monitors within approximately two weeks of their strokes. Scientists found that although brain stem injuries were present in a relatively small number of participants, this minority group had significantly higher likelihood of having obstructive sleep apnea. While only 11% of stroke patients had a brain stem injury, 84% of those who did had obstructive sleep apnea. Only 59% of those whose brain stem wasn’t involved had obstructive sleep apnea.
The precise nature of the relationship between sleep apnea and brain stem injury from stroke is not clear. More research is needed to understand whether the presence of sleep apnea is a result of the brain stem injury and whether the presence of sleep apnea prior to stroke may increase the likelihood for this type of injury. It’s also worth noting that the prevalence of sleep apnea among people without brain stem injury, while lower, is still nearly 60% of the overall study group. These numbers further confirm the strong link between the presence of obstructive sleep apnea and stroke.
There is a compelling and growing body of evidence detailing the relationship between sleep-disordered breathing and stroke. Sleep apnea and other forms of sleep-disordered breathing are both a risk factor for stroke and a complication to contend with after stroke. Fortunately that also means that treating obstructive sleep apnea could lower the risk for future stroke.
It’s not only sleep-disordered breathing that poses greater risk for stroke. According to a recent research, insufficient sleep could also increase stroke risk. A study of more than 5,000 adults found that sleeping fewer than six hours nightly was associated with four times the risk for stroke compared with sleeping seven to eight hours a night.
Stroke is one of the leading causes of death in the U.S. Nearly 800,000 people suffer stroke and approximately 130,000 events are fatal. Obstructive sleep apnea is underdiagnosed and undertreated, leaving people at elevated risk for stroke and unaware of the hazards their sleep-disordered breathing poses. Raising awareness about the links between sleep apnea and stroke is important. So is the implementation of more rigorous screening for obstructive sleep apnea among stroke patients, and those with other risk factors for both stroke and sleep apnea. With awareness and diagnosis comes the opportunity to treat sleep apnea and lower its very serious health consequences.