Sleep apnea, the disorder that causes a person to stop breathing suddenly while sleeping, is already known to increase the risk of high blood pressure, heart failure, stroke and daytime sleepiness. And a new study suggests that the sleep disorder is also linked with small brain lesions and a symptomless form of stroke, known as silent stroke.
"We found a surprisingly high frequency of sleep apnea in patients with stroke that underlines its clinical relevance as a stroke risk factor," study researcher Dr. Jessica Kepplinger said in a statement.
In the small new study, which will be presented at the American Stroke Association's International Stroke Conference, researchers from Dresden University found that 91 percent of the patients in the study who have had a stroke, also had sleep apnea -- and these people were also at an increased risk for silent stroke.
Particularly, researchers found that having more than five episodes of sleep apnea in a night is linked with having silent stroke. More than a third of people who had the small brain lesions also had severe sleep apnea, and more than half of people who had a silent stroke also had sleep apnea.
"I think what we can say is that breathing problems are more common in stroke patients than suspected," Dr. Steven Greenberg, a neurologist at Harvard Medical School, told WebMD.
Researchers found the associations by conducting overnight testing on 56 people with an average age of 67. Brain imaging was conducted to determine the silent strokes and the brain lesions.
WebMD reported that between 20 and 25 percent of people age 60 and older have had a silent stroke before.
Silent strokes don't have any symptoms, meaning a person typically doesn't know he or she has suffered one, ABC News reported. Having multiple silent strokes is linked with memory loss, difficulties with walking and mood problems.
"Silent strokes are epidemic in this country," Dr. Megan C. Leary told ABC News. Even though they may be symptomless, "the word 'silent' should be put in quotes, because their effects accumulate over the years."