"We already know that stroke patients have an increased risk of recurrent stroke and dementia," explained study senior author Dr. M. Arfan Ikram.
"What we didn't know was whether this increased risk persists for a long time after stroke, and whether heart disease risk factors present before the first stroke influenced the risk of recurrent strokes or dementia," he added.
"Our study found these risk factors influence future stroke and dementia, and the risks persist for an extended period in some patients," Ikram said in an American Heart Association news release. He's associate professor in the department of epidemiology, neurology and radiology at Erasmus University Medical Center in Rotterdam.
In the study, Ikram's group compared data from a long-term study on more than 1,200 stroke survivors against data from about 5,000 people who hadn't had a stroke.
The investigators found that one year after having a stroke, survivors remained at high risk for another stroke over at least the next five years.
A year after their first stroke, survivors had triple the odds for another stroke compared to people without a prior stroke history, the researchers said. Stroke survivors were also nearly twice as likely to develop dementia as those who didn't have a stroke.
Poor heart health seems key. For example, among the stroke survivors, 39 percent of future strokes and 10 percent of dementia cases were linked to heart-related risk factors the patients had already been diagnosed with before their first stroke.
Those health issues included high blood pressure (hypertension), diabetes, low levels of HDL ("good") cholesterol, smoking or a history of "mini-strokes" -- what doctors call transient ischemic attacks, or TIAs, the researchers explained.
The findings weren't a big surprise to the study authors. "We found in a previous study that 27 percent of all deaths after stroke can be attributed to risk factors already present before stroke," Ikram said.
U.S. experts in brain health weren't surprised by the findings, either, but said there's much patients can do to lower their risk.
"What does this really mean? Put simply, it emphasizes once again the importance of controlling or treating one's vascular risk factors," such as giving up smoking and controlling blood pressure, said Dr. Richard Libman, a neurologist at Long Island Jewish Medical Center in New Hyde Park, N.Y.
"No one wants to have a stroke, but this study suggests that we all have some control in the form of preventing a second stroke and maintaining our mental faculties," he said.
Dr. Ajay Misra practices neurology at Winthrop-University Hospital in Mineola, N.Y. He said that the "most important take-home message is that efforts should be directed towards primary prevention of cardiovascular risk factors -- to prevent the stroke in the first place."
The findings were published online July 14 in the journal Stroke.
The American Stroke Association explains more about the risk factors for stroke.
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