WEDNESDAY, Feb. 18, 2009 (HealthDay News) -- "Silent strokes" rarely produce symptoms, but a new study suggests they may be at least five times more common than full-blown strokes in people under 65 years of age, and not uncommon in people under the age of 50.
The new study was conducted by a team at Boston University School of Medicine as a part of the ongoing Framingham Heart Study. The researchers performed brain MRI's on 1,059 people and then followed 925 individuals who showed no evidence of silent stroke, known as silent cerebral infarcts (SCI). The mean age of study participants was 64 years, with women making up slightly more than half of those studied.
After five years, the researchers observed evidence of silent strokes in 10.2 percent of participants and full-blown, clinical stroke in 1.5 percent of participants. The incidence of SCI was more than five times higher in people younger than 65, although both SCI and clinical stroke increased with age. And, while no clinical strokes were seen in those younger than 50 years old, 2.4 percent showed evidence of having suffered an SCI.
These so-called silent strokes are "really not silent," said lead study author Dr. Jose Rafael Romero, an assistant professor of neurology at Boston University School of Medicine. "What we saw is that the [brain] damage caused by the silent stroke can be seen by the MRI."
"We don't really have a way of ordinarily recognizing this sort of thing, but if it's part of the brain that's not directly involved with motion or our speech, it could impact memory or the mood of the person," added one expert, Dr. Norman Kaplan, clinical professor at the University of Texas Southwestern Medical Center in Dallas. "There are all sorts of parts of the brain that are not so obvious in what they reflect but nevertheless make up who a person really is."
Indeed, stroke researchers point out that those who suffer from silent strokes appear more likely to experience other health problems. "By nature, the [strokes are] very small. But if they happen to occur in a specific part of the brain, then they can produce symptoms that may make somebody suspect," Kaplan said.
The research was to be presented Wednesday at the American Stroke Association's International Stroke Conference in San Diego.
While researchers point out that most people who have an SCI will not show obvious symptoms, identifying at-risk individuals could help them make changes that might curb their odds for stroke.
"The main risk factor is hypertension and, in some studies, smoking," said Romero. "The problem is that transferring the theory into practice is very difficult, because people don't realize they have high blood pressure and we have problems with compliance."
The researchers stressed that further research is needed and they do not advise healthy people to rush out to get a MRI.
"Based on this data, we cannot say that everyone should have a MRI," said Romero. "We need more studies."
In addition, he noted, "Most of the participants come from European descent, so the results cannot be generalized to other types of populations, to Hispanics to African-Americans for example."
"We're going to looking at clinical markers of disease, but we're not there yet," he said. "The next step is to move on to trials where you can do an intervention and measure how effective it is at preventing."
To read more about strokes, visit the American Stroke Association.