American Journal erf Epidemiology
Copynght C 1999 by The Johns Hopkins University School of Hygiene and Public Health
All rights reserved
Vol. 150, No.12
Printed In U.S.A.
REVIEW
Risk Factors for Stroke in Blacks: A Critical Review
Richard F. Gillum
Stroke is the third leading cause of death in US Blacks and is an important cause of mortality and morbidity
worldwide. Mortality rates are higher in Blacks than in Whites in the United States at ages below 70 years. In
Blacks, advanced age, elevated blood pressure, diabetes mellitus, and smoking are the only risk factors for
stroke whose status has been firmly established by published data. More data are needed to assess other likely
risk factors of importance for risk stratification and intervention and to determine the fraction of racial differences
in stroke that may be explained by risk factor differences. Higher prevalences of hypertension, diabetes, obesity
(in women), elevated lipoprotein(a) level, smoking (in men), and low soctoeconomic status may contribute to the
higher stroke incidence and mortality in US Blacks as compared with Whites. However, further environmental
influences must be studied and candidate genes identified before assuming that racial differences can be
attributed to inborn susceptibility linked to inheritance of specific genes. Am J Epidemiol 1999; 150:1266-74.
blacks; cerebrovascular disorders; risk factors
Stroke is the third leading cause of death in US
Blacks (1). It is an important cause of mortality and
morbidity in Blacks worldwide (2). Since 1914, US
vital statistics have shown higher mortality from stroke
in Blacks than in Whites; differentials have persisted
as diagnostic technology has developed over the century
(3-6). The excess stroke mortality in Blacks is greatest
at ages 45-64 years, with little difference in mortality
rates above age 70 (4-19). In the 1960s, stroke death
rates for US Blacks were among the highest in the
world (3); in 1990, they fell between the high rates of
Eastern Europe and the low rates of North American
Whites (4, 7-9). Stroke is an important contributor to
the higher all-cause mortality seen in US Blacks as
compared with Whites (1, 10). Despite these facts,
many questions remain regarding the etiology of
stroke in Blacks and the basis for racial differences in
stroke occurrence (4, 11). In this report, data on risk
factors from the US National Center for Health
Statistics are examined and epidemiologic studies of
stroke in Black populations are reviewed in an attempt
to critically examine the current state of knowledge
and to suggest directions for future research and prevention.
Blood pressure
Among Blacks in developed countries, elevated
blood pressure is the best established risk factor for
stroke in terms of strength and consistency of findings,
meeting epidemiologic criteria for a causal relation (4,
6). It is also the most important factor in terms of
population attributable risk and potential for modification (4—7, 15, 20-57). Several prospective cohort studies have estimated the relative risk for stroke associated with elevated blood pressure in Blacks. In a
national sample, the First National Health and Nutrition
Examination Survey (NHANES I) Epidemiologic
Follow-up Study, systolic blood pressure was similarly
significantly related to stroke risk in Blacks and Whites
(25, 26, 53). In Black men screened for the Multiple
Risk Factor Intervention Trial, a 10-mmHg increase in
diastolic blood pressure increased stroke risk by 86
percent, significantly more than the 45 percent
increase seen in White men (22, 37). In a large health
maintenance organization cohort, the adjusted relative
risk of hospitalization for cerebral thrombosis with a
10-mmHg increase was 1.14 (95 percent confidence
interval (CI): 0.97, 1.33) in Blacks and 1.14 (95 percent Cl: 1.00, 1.29) in Whites (27). Thus, elevated
blood pressure is a powerful risk factor for stroke in
Received for publication July 30, 1998, and accepted for publication April 14, 1999.
Abbreviations: Cl, confidence interval; DASH, Dietary Approaches to Stop Hypertension; NHANES I, First National Health
and Nutrition Examination Survey; TIA, transient ischemic attack.
From the Centers for Disease Control and Prevention, National
Center for Health Statistics, 6525 Belcrest Road, Room 730,
Hyattsville, MD 20782. (Reprint requests to Dr. Richard F. Gillum at
this address).
1266
Stroke in Blacks
Blacks, probably similarly to Whites in relative terms
but with greater effect in terms of the number of cases
explained.
The epidemiology of hypertension in Black populations
has been well documented elsewhere (1, 7, 8, 12, 20-57).
Prevalence, incidence, and blood pressure levels are
higher in Blacks than in Whites. In 1988-1994, the ageadjusted prevalence among US adults aged 20-74 years
was 33.8 percent for Black women, 19.3 percent for White
women, 34.9 percent for Black men, and 24.3 percent for
White men (1). In the 1985 National Health Interview
Survey, 79 percent of Blacks and 77 percent of Whites
correctly identified hypertension as the most significant
cause of stroke (45). Data from the 1990 National Health
Interview Survey showed no further improvement in the
public's knowledge about the causes of stroke, and possibly a slight decline, with 72 percent of Blacks and 73
percent of Whites correctly identifying hypertension as
the most significant cause of stroke (D. Rose, National
Center for Health Statistics, personal communication,
1998). In the Third National Health and Nutrition
Examination Survey, hypertension awareness, treatment,
and control rates in 1992-1994 failed to improve beyond
rates observed in 1988-1991 (21). Despite the marked
improvements in detection and control of hypertension
over the past two decades, the still unsatisfactory rates for
hypertension among Black men, the lack of further
improvement in the 1990s, and suboptimal knowledge
levels suggest that considerable work is still needed to
control hypertension in Black communities.
Clinical trials in over 47,000 subjects have provided
conclusive evidence that antihypertensive treatment is
effective in preventing stroke in Blacks and Whites (7,
48, 49). Meta-analysis of data from five randomized
clinical trials that reported results separately by race
revealed no indication of a differential effect in Blacks
(32 percent reduction in stroke occurrence) versus
Whites (37 percent reduction) (49). Although the efficacy of hypertension treatment in preventing stroke in
the setting of a clinical trial seems established, ecologic
studies have been unable to consistently demonstrate
an effect at the community level (51). More data on the
efficacy of hypertension treatment in Black and White
stroke survivors are needed (36, 40). In the
Hypertension Detection and Follow-up Program,
results suggested that blood pressure treatment and
strict control might largely eliminate racial differences
among women, but further analyses on this point are
needed (48, 55).
Diabetes mellltus
Several recent studies have found diabetes mellitus
to be an important risk factor for stroke in Blacks. In
the NHANES I Epidemiologic Follow-up Study,
Am J Epidemiol
Vol. 150, No. 12, 1999
1267
a history of diabetes was similarly associated with
increased risk of stroke in Blacks (relative risk = 2.5
for men and 2.4 for women) and Whites (25). In the
health maintenance organization cohort, serum glucose level was predictive of cerebral thrombosis in
Blacks (27). No data were found on the relation
between glucose intolerance or diabetes assessed by
glucose tolerance testing and stroke in Blacks.
The epidemiology of diabetes in Blacks has been
reviewed elsewhere (58, 59). In the United States,
non-insulin-dependent diabetes mellitus is more
prevalent in Blacks than in Whites (1). Recent national
data have indicated a higher prevalence of diagnosed
and undiagnosed diabetes in Blacks than in Whites.
Furthermore, the relations between the fourfold
increase in Black Americans' rate of known diabetes
between 1963 and 1985 and trends in stroke and
ischemic heart disease mortality require study (15).
Prior heart disease and electrocardiographs
abnormalities
Prior heart disease is an established risk factor for
stroke in populations of European descent; however,
few studies have addressed this question in Blacks (4,
26, 57, 60). This subject is discussed at length elsewhere (61). Available data suggest different modes of
action for this risk factor in Blacks and Whites, perhaps related to greater prevalence of hypertensive
heart disease in Blacks and myocardial infarction in
Whites (26). Atrial fibrillation is a powerful risk factor
for stroke among Whites; its role in stroke among
Blacks has not been adequately studied. A study of 4
million Medicare recipients followed for 4 years
revealed that, compared with those without atrial fibrillation, Black men and women with atrial fibrillation
had 1.4 and 1.7 times the risk of nonembolic stroke
and 4.3 and 7.3 times the risk of embolic stroke,
respectively (39). Four-year risks were highest among
Black women with atrial fibrillation (21.3 percent for
nonembolic stroke and 3.28 percent for embolic
stroke). The associations were similar in Whites.
Similarly, little is known about coronary disease and
congestive heart failure as stroke risk factors in
Blacks. In a series of stroke patients, Blacks tended to
have less atrial fibrillation and coronary disease than
Whites and a similar frequency of heart failure (60). In
one cohort, a history of heart disease was a significant
risk factor for stroke in Whites but not in Blacks (26).
The effectiveness of antithrombotic and antiplatelet
therapy for atrial fibrillation or other forms bf heart
disease has not been studied in Blacks.
In developed countries, heart disease is the leading
cause of death in both Blacks and Whites; the prevalence of heart disease in these populations may be
1268
Gillum
similar in elderly Blacks and Whites. In developing
countries, heart disease and stroke are growing problems. The prevalence of hypertensive heart disease and
of echocardiographic and electrocardiographic abnormalities has been found to be higher in Blacks than in
Whites in the United States (9,61, 62). Atrial fibrillation
may be less prevalent in US Blacks than in US Whites
(39, 61).
Transient cerebral ischemia and large vessel
atherosclerosis
Few prospective studies have published data on transient cerebral ischemia or asymptomatic carotid bruits
as a precursor of stroke in Blacks (4, 6). Some cohort
studies report a lower incidence of transient ischemic
attack (TIA) in Blacks than in Whites (4, 57), while
cross-sectional studies report a similar or higher prevalence of history of TIA symptoms in Blacks than in
Whites (4, 63-65). No useful information has been
found on the strength of TLA or carotid atherosclerosis
as a risk factor for subsequent stroke in Blacks (4), but
several studies currently under way may provide such
data (64, 65). Utilization of carotid endarterectomy is
much lower in US Blacks than in US Whites (66).
Ankle-brachial index, an index of lower extremity arterial disease, is associated with prevalent stroke/TIA and
carotid atherosclerosis in Blacks and Whites (56).
Smoking
Tobacco use is the leading external (nongenetic)
factor contributing to death in the United States, and
it is an important risk factor for all types of stroke in
Whites (4, 6, 22, 37, 67-70). However, relatively few
data from prospective cohort studies are available for
Blacks. In the health maintenance organization
cohort, Black cigarette smokers of >1 pack/day had
four times the risk of stroke as never smokers (27). No
interaction of race with smoking was found for stroke
mortality among men in the Multiple Risk Factor
Intervention Trial (22). Given the importance of
smoking as a modifiable risk factor, further studies in
large cohorts of Black women as well as men are
needed. For example, the large cohorts of the
American Cancer Society would be excellent for studies that might examine possible interactions of smoking with other risk factors among Blacks.
In 1994, among US adults over age 18, the prevalence of cigarette smoking was 21.1 percent in Black
women, 24.3 percent in White women, 33.5 percent in
Black men, and 27.5 percent in White men (1). Thus,
cigarette smoking is of great importance, second only
to hypertension, as a stroke risk factor because of its
high prevalence and high relative risk.
Age, sex, hormone therapy, and genetic markers
Increasing age has been associated with increased
stroke mortality and morbidity in essentially all studies
of Blacks (1, 3-6, 13, 18, 22). In recent decades, male
sex was associated with higher stroke mortality at ages
under 75 years but was inconsistently associated with
morbidity (4, 57, 63, 71). Among Blacks in the health
maintenance organization cohort, males had a higher
risk of hospitalization for cerebral thrombosis than
females (27). However, prior to 1960, the age-adjusted
stroke death rate among Nonwhites in the United
States was higher for women than for men (3, 12), and
it was reported to be higher for women than for men
among "colored" (mixed race) people in South Africa
in 1978-1982 (72).
Reproductive history may influence stroke risk in
women. Women with six or more pregnancies had a 70
percent increased risk of stroke compared with nulligravid women (73). High dose estrogen oral contraceptives may increase the risk of stroke in women,
and postmenopausal estrogens may reduce the risk
(74, 75). However, no data on oral contraceptive use
or hormone replacement therapy and stroke risk in
Blacks were found. In recent years, the prevalence of
oral contraceptive use has been slightly lower in
Blacks than in Whites, and use of hormone replacement
therapy has been much lower (76, 77).
Population-based data on genetic markers and stroke
risk in Blacks were not found. In a multicenter study,
increased risk of stroke associated with a positive family history of stroke could not be shown to differ in
Blacks and Whites; however, the number of stroke
events in Blacks was small (n = 14) (78). Further
research in larger Black populations is needed.
Conditions affecting blood viscosity and
coagulation
Homozygous sickle cell disease, chiefly affecting
Blacks, is a risk factor for ischemic stroke because of
increased hemolysis and altered rheologic properties
of red blood cells which favor cerebral ischemia.
Stroke may affect 6-9 percent of children with sickle
cell anemia, although recent studies suggest a protective effect of multiple blood transfusions (79).
Concomitant alpha thalassemia appears to lower
stroke risk in these patients (80). Among Blacks in the
Evans County cohort, a positive association between
high hematocrit level and stroke was suggested (57).
No association was found in a national cohort (81), nor
was there an association with serum transferrin saturation, an indicator of body iron stores (82). Data on high
blood fibrinogen levels or other coagulation factors
and stroke in Blacks are limited. Fibrinogen was posiAm J Epidemiol Vol. 150, No. 12, 1999
Stroke in Blacks
tively associated with history of TTA or stroke in
Blacks but not in Whites in the Atherosclerosis Risk in
Communities Study (83). Racial differences in the
prevalence of abnormal levels of several coagulation
factors and indicators of platelet function in normal
persons and stroke patients indicate the need for further studies (34, 84).
Blood lipids
The relation between blood lipid levels and stroke
risk in Blacks has been insufficiently studied (4,
83-87). Serum total cholesterol was not related to
stroke incidence in Blacks or Whites in the Evans
County cohort (57), but a significant relation was
found with hospitalization for cerebral thrombosis in
the health maintenance organization cohort (27) and
with nonhemorrhagic stroke mortality in the Multiple
Risk Factor Intervention Trial cohort (22). An
increased risk of hemorrhagic stroke was found
in men with low serum cholesterol levels (22). In
Atherosclerosis Risk in Communities subjects aged
45-64 years, the prevalence of a self-reported history
of stroke/TLA was higher in Blacks than in Whites (3.0
percent vs. 2.0 percent), as were mean lipoprotein(a)
levels (160.5 ng/ml vs. 81.6 H-g/ml) (83). Lipoprotein(a) levels were statistically significantly higher
among persons with a self-reported history of
stroke/TLA for both races (in Blacks, 191.3 Jig/ml for a
stroke/TIA history vs. 159.6 |ig/ml for no history).
Lipoprotein(a) was also associated with carotid artery
wall thickness in Black men and diabetes in Black
women (85). Black stroke patients were reported to
have elevated levels of apolipoprotein AIC, and the
Sac I polymorphism in the AIC lipoprotein gene
cluster was more common in Blacks with carotid
stenosis than in those without it (11, 86). In the
Atherosclerosis Risk in Communities Study, serum
total cholesterol and low-density lipoprotein cholesterol
were not associated with prevalent TLA or stroke in
Blacks, but mean high-density lipoprotein cholesterol
was lower and triglyceride levels were higher in
Blacks with a stroke history than in those without such
a history (83). Serum total cholesterol was not a significant predictor of total stroke in several studies. No
data on lipoprotein levels and incidence of stroke subtypes
were found.
In 1988-1994, the prevalence of high cholesterol (mean
level >240 mg/dl) in the United States was 19.4 percent
for Black women, 20.2 percent for White women, 15.7
percent for Black men, and 17.8 percent for White men
(1); mean serum cholesterol levels were 203, 205, 199,
and 202 mg/dl, respectively. Recent clinical trials suggest
that P-hydroxy-P-methylglutaryl-coenzyme A reductase
inhibitors may lower the risk of stroke as well as of
Am J Epidemiol Vol. 150, No. 12, 1999
1269
coronary disease events, but data on Blacks are lacking (55). Thus, it seems likely that high lipoprotein(a)
and low high-density lipoprotein cholesterol, and
perhaps high low-density lipoprotein cholesterol, are
risk factors for ischemic stroke in Blacks. However,
more cohort studies of the relations of low-density
lipoprotein and high-density lipoprotein cholesterol,
apolipoproteins, and lipoprotein(a) to each stroke subtype
are needed.
Obesity and dietary factors
Obesity or overweight has not been shown to be a
risk factor for stroke independently of age, blood pressure, and other risk factors for stroke in Blacks (26, 27,
57). In the Evans County cohort, lean Black men had a
lower risk of stroke than obese Black men, but no such
relation was found in Black women (57). Obesity was
associated with increased risk of stroke in Whites, hi
the United States, the prevalence of overweight is
much higher in Black women (53.0 percent) than in
White women (33.9 percent) or Black (34.0 percent) or
White (34.3 percent) men (1).
Few data on dietary risk factors in Blacks have been
published. One striking finding was the strong protective effect of fish intake on stroke incidence and death
seen among Blacks in a national cohort (87) (figure 1).
Fish-eaters had only half the stroke risk of non-fisheaters and one fourth the risk of stroke death. This
exciting finding, with its important public health
Relative risk
Fish intake
• Never H
1.5
0.5
Incidence
Death
FIGURE 1 . Relative risk of acute stroke incidence and death associated with fish consumption in US Blacks aged 45-74 years:
NHANES I Epidemiologic Follow-up Study, 1971-1987. Relative
risks were adjusted for sex, baseline age, smoking, history of diabetes, history of heart disease, educational level (less than high
school graduation), systolic blood pressure, serum albumin concentration, serum cholesterol concentration, body mass index, and
physical activity. *p < 0.05; t P < 0.01. (Adapted from Gillum et al.
(87), Arch Intern Mod 1996; 156:537-42).
1270
Gillum
implications, should be confirmed by other studies. In
this same cohort, Whites with a serum folate concentration <9.2 nmol/liter had a relative risk of stroke of
1.18 (95 percent CI: 0.67, 2.08), whereas Blacks had a
relative risk of 3.60 (95 percent CI: 1.02, 12.71) (88).
Data on the relation of stroke risk to high sodium intake
or to low potassium, calcium, antioxidant vitamin, or
fruit and vegetable intake in Blacks were lacking.
However, the potential importance of nutritional factors
in stroke risk among Blacks is great, and expanded
research is urgently needed. Adherence to the Dietary
Approaches to Stop Hypertension (DASH) diet and
weekly intake of baked or broiled fresh ocean fish,
canned tuna, or salmon have been suggested as prudent
measures for Blacks at increased risk of stroke (55).
Alcohol intake and Illegal drug use
Alcohol intake has not been thoroughly studied as a
stroke risk factor in Blacks, and existing studies have
yielded inconclusive results. In the health maintenance
organization cohort, no significant association of usual
alcohol consumption with hospitalization for cerebral
thrombosis could be demonstrated for Blacks or
Whites (27). However, an earlier study from the same
group suggested an inverse association with occlusive
cerebrovascular disease in both Blacks and Whites
(68). A case-control study carried out in a predominantly (71 percent) Black sample indicated that
chronic or acute alcohol ingestion was associated with
increased odds of ischemic stroke, but after data were
controlled for smoking and hypertension the association was no longer significant (adjusted odds ratio =
1.68; 95 percent CI: 0.84, 3.35) (69). At ages 45 years
and over, fewer Blacks (24.5 percent of women, 51.3
percent of men) than Whites (44.0 percent of women,
65.5 percent of men) were alcohol drinkers in the
United States in 1990 (1). Among drinkers, 7.7 percent
of Blacks and 10.4 percent of Whites reported consuming 14 or more drinks per week. Further studies of
relations between acute and chronic alcohol intake and
the risk of each type of stroke, as well as studies of
cocaine and other illegal drugs, are needed (28).
Physical Inactivity and heart rate
Limited data suggest that physical inactivity and
high heart rate may be independent risk factors for
stroke in Blacks (89, 90). Low levels of physical
activity were associated with increased risk of stroke
in Blacks in a national cohort (89). This pattern was
consistent, although conventional levels of statistical
significance were not attained. In addition, a significant association of high pulse rate with a twofold
increased stroke risk was seen in Blacks (>84
beats/minute vs. <74 beats/minute; risk factor-adjusted
relative risk = 2.07 (95 percent CI: 1.25, 3.43)).
Further studies are needed to confirm these findings.
Indicators of inflammation and other biochemical
variables
New research on indicators of inflammation and
other biochemical analytes indicates that some may be
risk markers for stroke in Blacks. In a cohort study, no
association was found between white blood cell count
and stroke risk in Blacks (91). However, a high serum
albumin concentration (>4.4 g/dl) was associated with
a risk of incident stroke which was one half that seen at
low levels and a risk of stroke death which was one
fourth that seen at low levels (92) (figure 2).
Erythrocyte sedimentation rate was not associated with
stroke risk (93). Relations with hyperhomocysteinemia,
hyperuricemia, hypokalemia, and hypomagnesemia
require additional study in Blacks (26).
Socloeconomic status, region, and urbanization
Low socioeconomic status in the United States has
been related to increased hypertension prevalence,
blood pressure levels, and stroke mortality in both
Blacks and Whites (4, 10, 26, 94-97). In US Black
populations, an investigation of the variation in stroke
mortality trends from 1968 to 1987 among state economic areas categorized by socioeconomic structure
showed an inverse relation between the educational
achievement level of communities and stroke mortality (96). The difference in rates between the highest
Rate
30
Serum albumin, g/dL
• < 4.2 H 4.2-4.4 • > 4.4
20
10
Incidence
FIGURE 2. Fitted stroke incidence and death rates per 1,000
person-years for US Blacks aged 70 years, by serum albumin concentration (g/dl): NHANES I Epidemiologic Follow-up Study,
1971-1987. (Reproduced with permission from Gillum et al. (92), Am
J Epidemiol 1994;140:876-88).
Am J Epidemiol
Vol. 150, No. 12, 1999
Stroke in Blacks
and lowest educational achievement levels diminished
over time. In Blacks, a strong association between
increased stroke incidence and nonmetropolitan residence that was independent of region and other stroke
risk factors was demonstrated (98); the adjusted risk
was increased 60 percent in the Southeast and 110 percent in other regions. Reports relating season or climate
to stroke occurrence in Blacks were not found.
Risk factors in Africa
Although population-based data and analytic studies
from Africa are few, the prevalence of putative risk
factors among stroke patients, hospital patients, and
population samples has been reported (23, 30, 41, 43,
44, 71, 72, 99-101). For example, the MEDUNSA
Stroke Data Bank series of cases in South African
Blacks (with computed tomography utilized in 82.2
percent of cases) revealed that 71.2 percent had had
cerebral infarction (29). The prevalences of hypertension and increased age were similar to those in Western
stroke populations. Interestingly, a probable or definite
cardiac source for cerebral embolism was present in 46
percent of the patients. However, TLA, peripheral vascular disease, and coronary artery disease occurred
far less frequently than is reported in Western patients.
In young adults and children in Africa, infectious and
other nonatherosclerotic etiologies of stroke syndromes (e.g., syphilis, human immunodeficiency
virus, tuberculosis, and neurocysticercosis) remain
important. In African populations, hypertension predominates over risk factors related to affluence and
westernization, such as diabetes and smoking; however,
these factors are assuming increasing importance in some
urban areas.
environmental influences must be studied and candidate
genes identified before we assume that racial differences can be attributed to inborn susceptibility linked
to inheritance of specific genes.
Further research should be directed toward studying
racial variations in the susceptibility of various vascular
beds to hypertension and arteriosclerosis, as well as the
relative importance of blood pressure, diabetes, and
other putative risk factors (102). Risk factors for each
stroke subtype should be examined separately. For
example, higher levels of lipoprotein(a) in Blacks than
in Whites should be examined as a potential cause of
the higher incidence of lacunar stroke in Blacks.
Interactions among risk factors should be examined.
Large cohort studies of mortality or chronic disease
which include Blacks should include analyses of
stroke risk whenever possible. Given the cost, amount
of time, and logistic effort required for cohort studies,
increased use should be made of case-control studies
of stroke in Blacks (103). Sufficient numbers of Blacks
should be included in clinical trials to make subgroup
analyses possible (104, 105). Selected trials in allBlack or predominantly Black samples should be conducted (105). In addition to hypertension and diabetes
control and smoking cessation, dietary and lifestyle
interventions such as use of the DASH diet and
increases in fish intake and physical activity level
should be evaluated in prevention studies. Strategies for
primary and secondary prevention of stroke appropriate
for particular segments of the Black population must be
developed and vigorously implemented to reduce the
burden of premature mortality and morbidity due to
stroke among Blacks (106-109).
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Conclusions
Stroke is the third leading cause of death in US
Blacks and is an important cause of mortality and
morbidity worldwide. Below the age of 70 years,
mortality rates are higher in Blacks than in Whites in
the United States. Among Blacks, advanced age, elevated blood pressure, diabetes mellitus, and smoking
are the only risk factors for stroke whose status has
been firmly established by published data. More data
are needed to assess other likely risk factors of importance for risk stratification and intervention and to
determine the fraction of racial differences in stroke
that may be explained by risk factor differences. A
higher prevalence of hypertension, diabetes, obesity
(in women), elevated lipoprotein(a) levels, smoking
(in men), and low socioeconomic status may contribute
to the higher stroke incidence and mortality seen in
Blacks as compared with Whites. However, additional
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