WEDNESDAY, Feb. 1 (HealthDay News) -- Sleep apnea, the disorder
marked by abnormal pauses in breathing during sleep, is already
known to boost the risk of stroke. Now, a new study links sleep
apnea to so-called silent strokes, in which there is tissue death
in the brain without symptoms.
In another new study, researchers found that rapid memory loss
before a stroke boosts the risk of the stroke being fatal.
Both studies are slated for presentation Wednesday at the
American Stroke Association's International Stroke Conference in
Stroke affects 795,000 Americans annually, according to the
In one study, Dr. Jessica Kepplinger, a fellow at the University
of Technology in Dresden, Germany, and her colleagues evaluated 56
patients who had a stroke. They knew that silent strokes had been
linked to an increased risk of strokes. However, "there are barely
any studies that have investigated the relationship between sleep
apnea and the so-called clinically silent strokes," she said.
To look at the relationship, they first gave patients
in-hospital testing for apnea. "We found an overall high frequency
of sleep apnea, 91 percent, in our study population of acute stroke
patients, which underlines the importance of this stroke risk
factor," Kepplinger said.
The team also performed brain-imaging studies. Those with sleep
apnea were more likely to have the silent strokes, as evidenced on
the brain scans, the researchers found. Having more than five
episodes a night was linked with having silent strokes. The higher
the severity of the apnea, the more likely these silent strokes
were found on brain imaging.
The more severe the apnea, the less favorable the outcome when
the patient was discharged.
The patients were on average 67 years old, and just over half of
them were women, the study authors noted.
While the study found an association between sleep apnea and
stroke, it did not prove a cause-and-effect relationship.
In the second study, Qianyi Wang, a graduate student at the
Harvard University School of Public Health, and colleagues
evaluated nearly 12,000 men and women, all above age 50, enrolled
in the U.S. Health and Retirement Study.
All were stroke-free at the start. The men and women were given
memory tests every two years for up to 10 years.
Over time, 1,820 strokes were reported, including 364 people who
died after the stroke.
The others were stroke-free for the entire follow-up period, the
study authors noted.
The research looked at the memory declines over time. Those who
later survived a stroke "had memory decline that is nearly twice as
fast as stroke-free individuals, even before their stroke," Wang
"For people who do not survive stroke, this difference is even more striking," said M. Maria Glymour, an assistant professor of society, human development and health at Harvard and a study co-author. "Prior to stroke, people who later died shortly after stroke were declining three times as fast as the stroke-free."
The study was funded by the U.S. National Institute on Aging and
the American Heart Association.
"Our study is the first national picture of how memory changes over the long-term before and after stroke onset, compared to individuals who do not have a stroke," Glymour said.
Both studies provide some valuable information, said Dr. Ralph
Sacco, chair of neurology at the University of Miami Miller School
of Medicine and past president of the American Heart Association.
He reviewed the findings.
"It's been mainly in smaller studies that sleep apnea has been shown to be a risk factor for stroke," Sacco said. The new research, he noted, goes even further by linking sleep apnea with the milder "silent" strokes.
"There are many reasons to treat sleep apnea, including reducing the risk for clinical and now silent stroke," Sacco said.
The memory-loss study, he said, "is telling us that those who
have the worst memory loss may have a greater death rate when they
have the stroke." Those with more memory loss in the study may also
have had more risk factors for stroke, Sacco added.
Even so, he said, the message seems to be that taking care of
brain health may help us in several ways. "What is good for our
memory may also be good for surviving a stroke," Sacco said.
Because these studies were presented at a medical meeting, the
data and conclusions should be viewed as preliminary until
published in a peer-reviewed journal.
Visit the American Stroke Association to learn more about