Feb. 1, 2012 -- A common sleep disorder is associated with an increased risk of symptomless but serious strokes called “silent strokes,” German researchers report.
Sleep apnea, a condition marked by periodic interruptions in breathing during sleep, has been linked to an increased risk of strokes. But there hasn't been much research exploring the relationship between sleep apnea and silent strokes, says researcher Jessica Kepplinger, MD, of Dresden University Stroke Center at the University of Technology in Dresden, Germany.
So, Kepplinger and colleagues studied 56 men and women, aged 44 to 75 years, who’d had a stroke or mini-stroke known as a transient ischemic attack. All were given a screening tool that picks up changes in breathing during sleep.
Ninety-one percent periodically stopped breathing while they slept.
Then the men and women underwent brain imaging scans. Just over half had little areas of tissue death in the brain that had occurred in the past without a history of corresponding stroke symptoms -- evidence, Kepplinger tells WebMD, of silent stroke.
The more times a person stopped breathing during the night, the greater the likelihood of silent stroke, she says.
There was no comparison group, so researchers don't know how many people of the same ages and health status who don't have sleep apnea have had silent strokes.
MRI brain imaging studies suggest about 20% to 25% of people over age 60 have had a silent stroke, according to Harvard Medical School neurologist Steven Greenberg, MD, PhD. They have been linked to memory loss in some people, he says.
The study offers "good evidence linking" sleep apnea to silent stroke, Greenberg tells WebMD. But this is just an observation of an association between the two that needs further study, he says.
Greenberg moderated a news briefing to discuss the findings at the American Stroke Association's International Stroke Conference.
The study is small and preliminary. But it poses a number of questions that deserve further research, says Harvard neurologist Lee Schwamm, MD.
"I think what we can say is that breathing problems are more common in stroke patients than suspected," he tells WebMD.
"But is abnormal breathing during sleep a long-term problem in these patients? Or will it go away? And is abnormal breathing a risk factor that leads to stroke? Or is it a consequence of stroke?" Schwamm asks.
Kepplinger plans further study. In the meantime, she says, all stroke patients should be screened for sleep apnea.
These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.