SAN DIEGO — Silent cerebral infarction occurs in midlife more than five times as often as clinical stroke, according to an analysis of data from the Framingham Heart Study.
“Silent cerebral infarcts have been referred to as 'silent' because patients and/or clinicians may not recognize them when they occur, but silent infarcts are associated with a higher risk of cognitive impairment and clinical stroke,” Dr. Jose Rafael Romero said in an interview at the International Stroke Conference. “Given that hypertension is the main risk factor associated with higher risk of silent cerebral infarcts [SCIs], and is a modifiable risk factor, early surveillance and treatment should be emphasized. Our study supports the recommendation by several guidelines for early treatment of hypertension and surveillance.”
Dr. Romero, of the department of neurology at Boston University, and his colleagues studied 1,485 participants in the original Framingham cohort and their offspring. They were free of stroke or transient ischemic attacks and had undergone two brain MRI scans at least 1 year apart, in 1999–2003 and 2004–2006. SCI was defined as a lesion greater than 3 mm with hyperintense signal on T2-weighted images and cerebrospinal fluid signal intensity on subtraction images, separate from the circle of Willis vessels and perivascular spaces. Clinical stroke was determined by prospective ongoing surveillance using standard protocols. The mean age of the patients at baseline was 63 years, 46% were women, and 40% had hypertension.
Over a mean follow-up of 5 years, SCI was observed in 8.7% of study participants while clinical stroke occurred in 1.7% of study participants. The majority of SCIs (83%) were single incident in nature.
An age-stratified analysis revealed that the incidence of SCI was more than five times that of clinical stroke among those younger than 65 years of age (4.8% vs. 0.9%, respectively). The incidence of both SCI and stroke increased among those aged 65–74 years (13% vs. 2.8%, respectively) and those aged 75 years and older (16.9% vs. 3.2%).
“Our study adds to what is known about incident SCI by including younger persons,” Dr. Romero said, because the Framingham Heart Study participants are nearly a decade younger than those of prior studies of silent infarcts. “Hypertension appears to be the main stroke risk factor associated with a higher risk of incident SCI.” A significant link between hypertension and higher risk of incident SCI was observed in those older than 65 years (odds ratio 1.75).
A key limitation of the study is that the participants were primarily of European descent, Dr. Romero said at the conference, which was sponsored by the American Heart Association.
The study was supported by grants from the National Institutes of Health.
'Silent infarcts are associated with a higher risk of cognitive impairment and clinical stroke.' DR. ROMERO