normal sinus rhythm and left ventricular
hypertrophy (LVH) by voltage criteria. The brain CT scan showed old lacunar strokes but no evidence of acute ischemic changes or bleeds. The brain magnetic resonance imaging (MRI) revealed the presence of a small, acute left-sided capsular stroke, chronic ischemic changes, and evidence of prior brain hemorrhage. Whereas echocardiography showed LVH, magnetic resonance angiography (MRA) showed high-grade occlusive disease of the horizontal portion of the middle cerebral artery.
Case vignette discussion
The patient described illustrates key features that may occur in African-Americans with stroke. These include a high prevalence of hypertension and other cardiovascular risk factors, which may include dyslipidemia, obesity, diabetes mellitus, and cigarette smoking; nonoptimally controlled risk factors;
history of cerebral hemorrhage; and lacunar stroke subtype and intracranial occlusive disease. These and other topics germane to stroke in blacks are discussed.
Introduction
Blacks and other racial and ethnic minorities may be disproportionately affected by stroke. Disparities in their level of general health and access to health care in the United States continue to exist [1–6]. African- Americans have approximately two times the stroke risk as compared with their white counterparts, as well as lower life expectancy, poorer health care, and discrimination in the medical care system [3]. Of the three leading causes of mortality, the black-to-white ratio of death is greatest for stroke [1]. The US Insti- tute of Medicine concluded that racial and ethnic minorities receive lower quality of health care than others even after access to healthcare-related factors are taken into account [5]. Furthermore, medical care for minorities may be poorly matched to their needs based on language barriers, geography, cul- tural issues, stereotyping, biases inherent to the healthcare system, and uncertainty on the part of healthcare providers [5]. These gaps may be overcome by comprehensive, multilevel healthcare system strategies.
In this chapter, we discuss the prevention, diagnosis, and treatment of stroke in blacks.
Although blacks traditionally have been underrep- resented in clinical trials, more recent focused trials have helped us to better understand stroke prevention and treatment in this important group.
A theme of barriers to participation in clinical trials and the healthcare system has emerged for blacks, and we recommend means to overcome these challenges.
Descriptive epidemiology
White male Black male White female Black female
1940 1950 1960 1970 1980
Year
Mortality rate (per 100,000)
1990 2000 2010 250
200
150
100
50
0
Fig. 10.1 Death rates for cerebrovascular diseases by sex and race in the United States from 1950 to 2004 (data obtained from the National Center for Health Statistics [8]).
>85 75–84 Years
65–74 55–64
45–54 0 0.5 1 1.5 2 2.5 3 3.5 4
Ratio (black/white)
Men Women
Fig. 10.2 Stroke mortality ratios by sex and age for the year 2004 (data obtained from the National Center for Health Statistics [8]).
United States (North Carolina, South Carolina, Georgia, Tennessee, Mississippi, Alabama, Louisiana, and Arkansas) [12]. Within the stroke belt, mortality rates reach the absolute highest level in the stroke buckle, a region that includes the coastal plains of North Carolina, South Carolina, and Georgia (Figure 10.3) [12]. The excess in stroke mortality for blacks is substantially greater in south- ern than in nonsouthern states, and this difference
is more pronounced in younger patients. The black- to-white stroke mortality ratios for men (southern vs. nonsouthern states) are 3.24 versus 2.76 at age 55–64, 2.19 versus 1.81 at age 65–74, and 1.45 versus 1.22 at age 75–84. Similar results have been observed in women [14].
A National Institutes of Health (NIH)-funded study, Reasons for Geographic and Racial Differ- ences in Stroke Study (REGARDS), is being con- ducted in an attempt to understand the causes for excess stroke mortality in the southeast United States and among blacks [12]. It is hypothesized that geographic and racial differences in the awareness, treatment, and control of hypertension, which is considered the major risk factor for stroke, may be the main underlying factors contributing to the reported disparities in stroke mortality. Data from REGARDS suggest that blacks have higher aware- ness and treatment but poorer control of hyperten- sion than whites [15]. Therefore, the improvement of blood pressure control may provide a window of opportunity to reduce the racial disparity in stroke mortality. REGARDS, however, found no geo- graphic differences in awareness and treatment of hypertension [15]. In fact, a trend toward better control of this risk factor within the stroke belt was noted. This implies that a regional difference in
hypertension management may not be a major con- tributor to excess in stroke mortality in the south- east United States.
An interesting observation from the Health and Retirement Study is that residence in the stroke belt during childhood increases the risk of stroke in adulthood, even for those who leave the region [16].
If the stroke belt is primarily caused by a higher prevalence of artherosclerotic risk factors, it might not explain the high risk of stroke for those who migrate from the area. Similar to adults, children who live in the southeastern United States have a higher stroke mortality rate compared with non- southeastern US children (relative risk [RR] 1.21;
95% confi dence interval [CI] 1.12–1.29) [17]. This suggests that factors other than cardiovascular risks could be active in the stroke belt.
There has been a trend toward a slowdown in the decline of national death rates for cerebrovascular diseases in whites and blacks since the 1980s (Figure 10.1). Important fi ndings from the Greater Cincin- nati/Northern Kentucky Stroke Study (GCNKSS)
are illustrative. In the GCNKSS, the 30-day case-fatality rates after the fi rst ischemic stroke, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH) for whites and blacks did not change signifi cantly during the 1990s despite the increased use of medications to modify stroke risk factors (e.g., aspirin, antihypertensive medications, oral hypoglycemics, and lipid-lowering agents) [18].
The nature of the failure to translate risk-factor management into substantial decreases of stroke- related mortality is a source of debate. This fi nding may be explained, at least in part, by taking into account stroke incidence rates. Data from the GCNKSS suggest that the higher stroke-related mortality in blacks for all categories (ischemic, ICH, and SAH) is attributable to higher stroke incidence rates rather than to increased case fatality [10].
Other plausible causes to explain the higher mortal- ity in blacks beyond hypertension include subopti- mal risk factor control, stroke severity and/or subtype, increased prevalence and severity of comor- bidities, differences in stroke evaluation and
New York City
District of columbia
Age-adjusted average annual deaths per 100,000
61–113 114–123 124–133 134–146 147–241 Insufficient data
Fig. 10.3 County age-adjusted annual stroke death rates for individuals aged 35 years or older. Increasing intensity represents higher death rates (see insert) (modifi ed from Casper et al. [13]).
treatment, limited access to medical care, and race–
ethnic differences in response to stroke therapies.
Prevalence
The Behavioral Risk Factor Surveillance System (BRFSS) is a state-based, random-digit dialed tele- phone survey of the noninstitutionalized US civilian population aged ≥18 years. BRFSS is administered by state health departments in collaboration with the Centers for Disease Control. According to the 2005 BRFSS, 2.6% of the adults surveyed had a history of stroke [19]. Stroke prevalence was similar between men and women and increased with age:
0.8% between ages 18 and 44, 2.7% between ages 45 and 64, and 8.1% above the age of 65. Substantial differences were observed among race–ethnic groups, with an overall stroke prevalence of 4% in blacks and 2.3% in whites. Middle-aged women have about 2.5 times the prevalence of stroke than men in the United States with stroke prevalence being higher in the United States as compared with the corresponding rates in representative European countries [20,21]. The higher stroke prevalence rates in the United States are driven by higher prevalence rates among African-Americans, though white Americans have higher stroke prevalence rates than Europeans [21]. Furthermore, according to the 2003 BRFSS, the prevalence of stroke was higher in the 10 southeastern states than in the other states surveyed.
The highest age-adjusted prevalence of stroke was found in southeastern blacks (3.4%), followed by nonsoutheastern blacks (2.8%), southeastern whites (2.5%), and nonsoutheastern whites (1.8%) [22].
The Atherosclerosis Risk in Communities (ARIC) Study is an NIH-funded initiative to investigate the cause, natural course, and clinical consequences of atherosclerosis. In this study, the overall prevalence of silent cerebral infarction (SBI) in subjects aged 55–70 years – diagnosed with brain MRI – was 11%
[23]. After adjusting for risk factors (hypertension, elevated triglycerides, low HDL, and diabetes) and lifestyle choices (dietary fat intake, reported leisure- time physical activity, alcohol intake, and body mass index [BMI]), SBI was more prevalent among black participants than in whites (odds ratio [OR] 1.64;
95% CI 1.12–2.41). Recently, the tri-racial Northern Manhattan Stroke Study (NOMASS) reported the overall prevalence of SBI to be almost 18%. In this cohort, age, male sex, and hypertension were inde-
pendently associated with SBI. Signifi cant racial dis- parities were noted as blacks had an age-adjusted SBI prevalence of 24.5%, whereas whites had one of 17.6% [24].
Incidence
About 780,000 Americans experience a stroke each year. Of these, 600,000 are fi rst attacks, and 180,000 are recurrent attacks. Furthermore, it is estimated that a new stroke occurs in the United States every 40 seconds [7].
Data from large population-based stroke studies, such as GCNKSS, ARIC, and NOMASS, indicate that stroke incidence is not uniformly distributed among different race–ethnic groups, with blacks having a disproportionate burden compared with whites [10,25–27]. NOMASS found the overall annual age-adjusted incidence of stroke in blacks aged ≥20 to be 2.4 times higher than in whites. The incidence of ischemic stroke in blacks was two times higher for men and three times higher for women compared with their white counterparts. A similar disparity was noted in ICH. Also, blacks had an excess incidence of SAH, but the small number of events prevents defi nitive conclusions [27]. A similar trend was noted in the GCNKSS, in which the adjusted incidence rates for all stroke categories (either ischemic, ICH, or SAH) were almost two times higher for African-Americans. Similar to stroke mortality, the disparity between stroke inci- dence in blacks and whites is a phenomenon inversely related to age (RR 5.0, 95% CI 3.9–6.1 for ages 35–44; RR 2.2, 95% CI 1.6–2.8 for ages 55–64;
RR 1.3, 95% CI 1.4–1.8 for ages ≥85) [10].
The estimated stroke/transient ischemic attack incidence rates (per 10,000) for ages 45–54, 55–64, and 65–74 years are 24, 61, and 122 for white men, 97, 131, and 162 for black men, 24, 48, and 98 for white women, and 72, 100, and 150 for black women, respectively [28].
Epidemiology of stroke in young adults
Several large population-based studies, such as the GCNKSS, the NOMASS, and the Baltimore- Washington Cooperative Young Stroke Study (BWCYSS) have shown that young black adults have a signifi cantly higher risk of stroke than their white counterparts. In NOMASS, the 30-day stroke mor- tality rate in the 25–44 year age strata was 33% in
blacks, whereas no cases were documented in whites.
In this age group, the annual stroke incidence was 25 (per 100,000) for blacks and 10 for whites, con- ferring a relative risk of stroke in blacks of 2.4 [11].
In the GCNKSS, the stroke incidence in the 35–44 year age group was 96 (per 100,000) in blacks and 19 in whites, and in the BWCYSS, the annual stroke rate for persons aged 15–44 years was 23 (per 100,000) in blacks and 10.3 in whites [10,29]. The excess burden of stroke in young African-Americans may have a substantial public heath impact based on associated direct (e.g., inpatient care, rehabilitation, follow-up care) and indirect (e.g., long-term dis- ability, lost years of productivity) costs of stroke.