ISC 2009: Silent Cerebral Infarcts Far Outnumber Symptomatic Strokes in Midlife

Caroline Cassels

March 05, 2009

March 5, 2009 (San Diego, California) — New findings from the Framingham Heart Study show that in middle age, silent cerebral infarcts (SCI) are 5 times more common than symptomatic stroke and represent a major, unmeasured portion of the burden of cerebrovascular disease in this population.

Presented here at the American Stroke Association International Stroke Conference 2009, the study showed that, among individuals younger than 65 years, the incidence of SCI was 4.7%, vs 0.9% for symptomatic stroke.

Dr. Jose Romero

"Silent infarcts are much more common than clinical strokes. Even in those younger than age 65, the incidence was about 5 times more common. We looked at this in the overall sample as well as by sex and age and found that even in individuals younger than age 50, SCIs were more common than symptomatic strokes," study investigator Jose Romero, MD, Boston University, Massachusetts, told Medscape Neurology & Neurosurgery.

In older adults, SCIs have been associated with cognitive impairment and an increased risk for symptomatic stroke and dementia, with a reported incidence of 12% to 18%. However, said Dr. Romero, the incidence in younger populations has not previously been reported.

"While there are a number of studies looking at the prevalence of SCI, there are only 2 other population-based studies looking at incidence, and this is the first to look at incidence in a younger cohort," said Dr. Romero.

He added that gaining a better understanding of SCI has potentially important clinical implications.

"Even though [SCIs] have been labeled as 'silent,' they are linked to a higher risk of cognitive impairment, dementia, and major stroke, so from a clinical perspective. they are not really 'silent' at all.

"Our finding that [SCIs] occur in younger people makes a strong case for increasing awareness of the risk factors in this group — particularly regarding the importance of effectively managing high blood pressure. This also means getting the message out to physicians that they need to be more aggressive in their surveillance and management of risk factors among younger patients," said Dr. Romero.

Not "Silent" At All

The study included 1485 participants from the Framingham Original and Offspring study who underwent brain magnetic resonance imaging (MRI) on 2 separate occasions.

All subjects were free of prevalent clinical stroke, transient ischemic attack (TIA), or other neurological conditions known to alter brain MRI. Subjects were followed for a mean period of 5.4 years for incident clinical stroke and SCI. Participants' average age was 63 years at study outset, and 54% were women.

Overall, the incidence of SCI was 8.7%, vs 1.7% for clinical stroke, over a mean follow-up period of 5 years. In addition, the majority of SCI lesions (83%) were single.

However, when analyzed by age, the incidence of SCI was 4.8% vs 0.9% for symptomatic stroke in those younger than 65 years.

Both SCI and clinical stroke increased with age, but the difference was only twice as great in those older than 75 years — 17.4% and 9.1% for SCI and clinical stroke, respectively. No clinical strokes were observed in individuals younger than age 50 years, but 2.4% had SCI, the authors report.

"Again, the main point is that this study should increase awareness of ischemic vascular disease in the brain and reinforce the fact that it is a common phenomenon that is not exclusive to the elderly,"said Dr. Romero.

The study was supported by the National Institutes of Health.

American Stroke Association International Stroke Conference 2009: Abstract P129. Presented February 18, 2009.

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