Published Online
on June 22, 2006

A more recent version of this article appeared on August 1, 2006

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Submitted on April 7, 2006
Revised on May 25, 2006
Accepted on May 30, 2006

Factors Associated With Geographic Variations in Stroke Incidence Among Older Populations in Four US Communities

Aiman El-Saed MD, PhD, MPH^*; Lewis H. Kuller MD, DrPH; Anne B. Newman MD, MPH; Oscar Lopez MD; Joseph Costantino DrPH; Kathleen McTigue MD, MS, MPH; Mary Cushman MD, MSc; and Richard Kronmal PhD

From the Department of Epidemiology (A.E., L.H.K., A.B.N.) University of Pittsburgh, Pa; the Department of Neurology (O.L.), University of Pittsburgh, Pa; the Department of Biostatistics (J.C.), University of Pittsburgh, Pa; Department of General Medicine (K.M.), University of Pittsburgh, Pa; the Department of Medicine (M.C.), University of Vermont, Colchester, Vt; and the Department of Biostatistics (R.K.), University of Washington, Seattle, Wash.

^* To whom correspondence should be addressed. E-mail: amest30{at}pitt.edu.

Background and Purpose--In the Cardiovascular Health Study (CHS), we previously observed lower stroke incidence in Allegheny County, PA compared with the other 3 study sites. The purpose of this study was to study possible reasons for the lower stroke incidence in Allegheny County.

Methods--CHS participants 65 years or older who were stroke-free at baseline (n=5639) were followed between 1989 to 1990 and 2000 for the development of stroke. Risk factors at baseline and their subsequent control were compared among both groups. Site-specific hazard ratios for stroke incidence were calculated using Cox regression models.

Results--The unadjusted hazard ratio for total stroke incidence in Forsyth County, NC; Sacramento County, CA; and Washington County, MD combined compared with Allegheny County, PA was 1.74 (95% CI: 1.42, 2.14). After adjustment for age and other traditional risk factors, there was modest reduction of the excess hazard in non-Allegheny sites compared with Allegheny County (hazard ratio=1.52, 95% CI: 1.17, 1.98). Between baseline and the seventh-year visits, control of hypertension, diabetes, lipids, smoking, atrial fibrillation and transient ischemic attack were similar across sites. White matter grade 3 on the baseline brain MRI was less common in Allegheny County (25.8% versus 36.3%, respectively; P<0.001) and accounted for 25% of the excess hazard in non-Allegheny sites compared with Allegheny County.

Conclusions--Site differences in stroke risk factors at baseline and subsequent control only partially explain site differences in stroke incidence. White matter grade as a possible integrated measure of exposure and control of risk factors may help in explaining geographic variations in stroke incidence.

Key words: epidemiology • geography • incidence • magnetic resonance imaging • risk factors • stroke

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Geographic Variations in Stroke Incidence and Mortality Among Older Populations in Four US Communities

Aiman El-Saed, Lewis H. Kuller, Anne B. Newman, Oscar Lopez, Joseph Costantino, Kathleen McTigue, Mary Cushman, and Richard Kronmal
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