More than 10% of a large group of middle-aged study participants who appeared otherwise healthy said they’d never had a stroke, either, but brain scans revealed evidence of silent cerebral infarction (SCI), also called a silent stroke.  Even though they come and go without making us aware of their presence, these silent strokes are not to be taken lightly.  They are brain injuries and indicate an increased risk of future strokes, which can lead to cognitive impairment and dementia.

The study participants who got the surprising news were part of a group of 2,000, whose average age is 62 and who are long-term participants in the Framingham Offspring Study, a continuation of the Framingham Heart Study.  As a part of the offspring study, participants get clinical examinations once every four to eight years.  They are the children of the participants in the original study.

Even in the absence of stroke symptoms, 10.7% of the 2,000 study participants showed lesions in the brain during a routine MRI scan.  Of the participants with lesions, 84% were found to have just one lesion.

Risk factors such as cigarette smoking, diabetes, age, systolic blood pressure, hypertension, and cardiovascular conditions including atrial fibrillation (AF) and left ventricular hypertrophy were found to be consistent with the findings of this study.  These risk factors had been isolated as a means of estimating the likelihood of  stroke over a 10-year period of time in the Framingham Stroke Risk Profile.

Of particular interest is the close association between AF and SCI revealed in this study.  Participants with AF were more than twice as likely to experience SCI than those without it but the research team says it is unknown at this time which occurred first, the SCI or the AF.

Also of note is the close association between systolic blood pressure, hypertension, and high levels of the amino acid, homocysteine, in the bloodstream of the participants who had strokes.

Further details of the study can be found in Stroke: Journal of the American Heart Association.  Funding was provided by the National Institute on Aging, the National Institute of Neurological Disorders and Stroke, and the National Heart, Lung, and Blood Institute.