Their new study included more than 7,200 Americans older than 65 who were given tests every three years to evaluate their short- and long-term memory, attention, awareness and other mental functions.
Those with lower test scores were 61 percent more likely to suffer a stroke than those with higher scores. Compared to whites, blacks with mental decline had a five-fold higher risk of stroke.
After a stroke, mental function declined nearly twice as fast as before a stroke. Stroke coupled with mental decline increased the risk of death, according to the study published Aug. 7 in the journal Stroke.
"Stroke in old age can be caused by poor cognitive function; whereas, faster decline in cognitive function can be caused by stroke," lead author Kumar Rajan, assistant professor of internal medicine at Rush University Medical Center in Chicago, said in a journal news release.
"Low cognitive function is generally associated with poor neurological health and brain function. Worsening of neurological health can lead to several health problems with stroke being one of them," he explained.
Previous research has shown that poor cardiovascular health can increase the risk of mental decline, but the researchers say this is the first study to show that mental decline can increase the risk of stroke.
The findings suggest that assessing seniors' memory and thinking skills could help identify those at risk for stroke, though the study only found an association between memory and stroke risk, without proving cause-and-effect.
"From a care standpoint, [thinking and memory] decline is not only a strong marker for neurological deterioration and physical health in older adults, but also serves as a marker for stroke in old age," Rajan said.
Stroke is the leading cause of disability in the United States and the fourth leading cause of death.
The U.S. National Heart, Lung, and Blood Institute has more about stroke.