Sleep apnea, the condition in which one suddenly stops breathing while sleeping, is already known to have deleterious effects on health, including memory loss and an increased risk of stroke. But a new study has found that the condition may have any even stronger link to strokes than previously thought.

The study, led by Dr. Jessica Kepplinger, a fellow at the University of Technology in Dresden, Germany, found a link between sleep apnea and 'silent' strokes, or those that cause tissue death in the brain without any noticeable symptoms. Dr. Kepplinger evaluated 56 patients who had suffered from acute strokes and found that 91 percent also suffered from sleep apnea. Using brain imagery, her team was able to determine that patients with sleep apnea -particularly those who had at least five episodes a night - were also much more likely to suffer silent strokes as evidenced on the brain scans.

Another new study - this one conducted by Qianyi Wang, a graduate student at the Harvard University School of Public Health - found that rapid memory loss before a stroke boosts the risk of the stroke being fatal.

For this study, Wang and his colleagues evaluated 12,00 men and women over the age of 50 that were currently enrolled in the U.S. Health and Retirement Study. Before the study, none of the participants had suffered from a stroke. The men and women were given memory tests every two years for up to 10 years. Over the course of the study, 1,820 strokes were reported, including 364 people who died after the stroke. Researchers found that participants who suffered from stroke also experienced rapid memory-loss at a rate almost double that of stroke-free patients. The numbers were even more striking in cases were the patients did not survive the stroke.

"Prior to stroke, people who later died shortly after stroke were declining three times as fast as the stroke-free," said M. Maria Glymour, an assistant professor of society, human development and health at Harvard and a study co-author.

Both studies were presented this week at the American Stroke Association's International Stroke Conference in New Orleans.

Study: Sleep apnea causes 'silent' strokes
Additional stroke research finds connection between rapid memory-loss and the likelihood that a stroke is fatal.