Stroke in a biracial population: the excess burden of stroke among blacks

The reasons for geographic and racial differences in stroke study: objectives and design

The REasons for Geographic And Racial Differences in Stroke (REGARDS) Study is a national, population-based, longitudinal study of 30,000 African-American and white adults aged > or =45 years. The objective is to determine the causes for the excess stroke mortality in the Southeastern US and among African-Americans. Participants are randomly sampled with recruitment by mail then telephone, where data on stroke risk factors, sociodemographic, lifestyle, and psychosocial characteristics are collected. Written informed consent, physical and physiological measures, and fasting samples are collected during a subsequent in-home visit. Participants are followed via telephone at 6-month intervals for identification of stroke events. The novel aspects of the REGARDS study allow for the creation of a national cohort to address geographic and ethnic differences in stroke.

Racial variations in location and risk of intracerebral hemorrhage

BACKGROUND AND PURPOSE

Risk factors for intracerebral hemorrhage (ICH) vary by location. Incidence rates of ICH are known to be higher in American blacks than whites, but how rates may differ by hemorrhage location is unknown. We sought to define incidence rates for different ICH locations in a biracial population.

METHODS

All hospitalized patients age > or =20 years with spontaneous ICH were identified in the Greater Cincinnati/Northern Kentucky metropolitan area from May 1998 to July 2001 and August 2002 to April 2003. Incidence rates per 100,000 persons were age, sex, and race adjusted as appropriate to the 2000 US population. Risk ratios (RRs) with 95% CIs were calculated from unadjusted incidence rates.

RESULTS

There were 1038 qualifying ICHs. Annual incidence rates per 100,000 persons > or =20 years of age were 48.9 for blacks and 26.6 for whites. Annual incidence rates per 100,000 blacks in lobar, deep cerebral, brain stem, and cerebellar locations were 15.2, 25.7, 5.1, and 2.9, respectively. Annual incidence rates per 100,000 whites in the same locations were 9.4, 13.0, 1.3, and 2.9. The greatest excess risk of ICH in blacks compared with whites was found among young to middle-aged (35 to 54 years) persons with brain stem (RR, 9.8; 95% CI, 4.2 to 23.0) and deep cerebral (RR, 4.5; 3.0 to 6.8) hemorrhage.

CONCLUSIONS

The excess risk of ICH in American blacks is largely attributable to higher hemorrhage rates in young and middle-aged persons, particularly for deep cerebral and brain stem locations. Hypertension is the predominant risk factor for hemorrhages in these locations.

Absolute stroke mortality burden for non-Hispanic non-Latino whites was disproportionately higher than expected simply based on the US population in 2001

BACKGROUND AND PURPOSE

The absolute burden of stroke is a major determinant of health care costs and should also be considered when developing and implementing effective health policy. This study evaluated the impact of specific racial-ethnic categorization on absolute stroke mortality burden and population percentages.

METHODS

In this population-based analysis, 2001 US data was used to compute absolute values of population and stroke mortality burden for white and black, and other racial-ethnic groups. To test the effect of age-mix, values were age-adjusted using the 2000 US standard population. The z test statistic was computed and a 2-tailed P value of <0.05 was considered significant.

RESULT

Whites comprised a majority of the 2001 absolute US stroke mortality burden and US population (86% and 82%, respectively). Surprisingly, nHnL whites comprised a much higher percentage of the absolute US stroke mortality burden than expected based on their percentage of the US population alone (81% and 69%, respectively; P<0.001). Age-adjustment indicated a contribution by age-mix, however, an age-independent residual component remained.

CONCLUSIONS

Specific race-ethnicity categorization significantly influences comparisons of the proportion of absolute stroke mortality burden to the population proportion. Accordingly, appropriate caution and care are needed when estimating the societal impact of conditions such as stroke.

Incidence and Short-Term Prognosis of Transient Ischemic Attack in a Population-Based Study

Background and Purpose— Transient ischemic attacks (TIAs) have been shown to be a strong predictor of subsequent stroke and death. We present the incidence and short-term prognosis of TIA within a large population with a significant proportion of minorities with out-of-hospital TIA.

Methods— TIA cases were identified between July 1, 1993 and June 30, 1994 from the Greater Cincinnati/Northern Kentucky population of 1.3 million inhabitants by previously published surveillance methods, including inpatient and out-of-hospital events. Incidence rates were adjusted to the 1990 population, and life-table analyses were used for prognosis.

Results— The overall race, age, and gender-adjusted incidence rate for TIA within our population was 83 per 100 000, with age, race, and gender adjusted to the 1990 US population. Blacks and men had significantly higher rates of TIA than whites and women. Risk of stroke after TIA was 14.6% at 3 months, and risk of TIA/stroke/death was 25.2%. Age, race, and sex were not associated with recurrent TIA or subsequent stroke in our population, but age was associated with mortality.

Conclusions— Using our incidence rates for TIA in blacks and whites, we conservatively estimate that ≈240 000 TIAs occurred in 2002 in the United States. Our incidence rate of TIA is slightly higher than previously reported, which may be related to the inclusion of blacks and out-of-hospital events. There are racial and gender-related differences in the incidence of TIA. We found a striking risk of adverse events after TIA; however, there were no racial or gender differences predicting these events. Further study is warranted in interventions to prevent these adverse events after TIA.

Ethnic Disparities in Stroke

BACKGROUND AND PURPOSE

Evidence for ethnic disparities in stroke incidence, severity, and mortality has continued to mount in recent years. However, the picture for disparities in acute management and rehabilitation remains more ambiguous. The objective of this report is to summarize current evidence from stroke epidemiology and studies focusing on disparities in stroke care and disability, suggesting courses for action.

METHODS

A comprehensive search of current literature on ethnic/racial variation in stroke incidence, mortality, and severity, as well as acute and postacute patient care was performed.

RESULTS

Recent evidence unambiguously reaffirms a greater burden of disease in stroke, greater mortality, and greater severity of strokes for blacks. Evidence for disparities in acute and postacute care is less conclusive, as is the evidence for disparities among other ethnic groups. Evidence for health disparities in stroke care across settings, regions, and the continuum of care varies considerably.

CONCLUSIONS

Minority ethnic groups have higher rates or more severe stroke, but variations in prognosis for clinical outcomes other than mortality remain less certain. There is considerable need for more studies that take into account regional ethnic variations in treatment and outcomes, and for better documentation of stroke outcomes among groups in addition to blacks. Dealing with ethnic disparities in stroke will be served by sustained attention to quality improvement in high-impact areas in stroke care, complemented by initiatives that promote cultural competence.

Epidemiology of ischemic stroke in patients with diabetes: the greater Cincinnati/Northern Kentucky Stroke Study

OBJECTIVE

Diabetes is a well known risk factor for stroke, but the impact of diabetes on stroke incidence rates is not known. This study uses a population-based study to describe the epidemiology of ischemic stroke in diabetic patients.

RESEARCH DESIGN AND METHODS

Hospitalized cases were ascertained by ICD-9 discharge codes, prospective screening of emergency department admission logs, and review of coroner's cases. A sampling scheme was used to ascertain cases in the out-of-hospital setting. All potential cases underwent detailed chart abstraction by study nurses followed by physician review. Diabetes-specific incidence rates, case fatality rates, and population-attributable risks were estimated.

RESULTS

Ischemic stroke patients with diabetes are younger, more likely to be African American, and more likely to have hypertension, myocardial infarction, and high cholesterol than nondiabetic patients. Age-specific incidence rates and rate ratios show that diabetes increases ischemic stroke incidence at all ages, but this risk is most prominent before age 55 in African Americans and before age 65 in whites. One-year case fatality rates after ischemic stroke are not different between those patients with and without diabetes.

CONCLUSIONS

Given the "epidemic" of diabetes, with substantially increasing diabetes prevalence each year across all age- and race/ethnicity groups, the significance of diabetes as a risk factor for stroke is becoming more evident. Diabetes is clearly one of the most important risk factors for ischemic stroke, especially in those patients less than 65 years of age. We estimate that 37-42% of all ischemic strokes in both African Americans and whites are attributable to the effects of diabetes alone or in combination with hypertension.

Excess stroke in Mexican Americans compared with non-Hispanic Whites: the Brain Attack Surveillance in Corpus Christi Project

Mexican Americans are the largest subgroup of Hispanics, the largest minority population in the United States. Stroke is the leading cause of disability and third leading cause of death. The authors compared stroke incidence among Mexican Americans and non-Hispanic Whites in a population-based study. Stroke cases were ascertained in Nueces County, Texas, utilizing concomitant active and passive surveillance. Cases were validated on the basis of source documentation by board-certified neurologists masked to subjects' ethnicity. From January 2000 to December 2002, 2,350 cerebrovascular events occurred. Of the completed strokes, 53% were in Mexican Americans. The crude cumulative incidence was 168/10,000 in Mexican Americans and 136/10,000 in non-Hispanic Whites. Mexican Americans had a higher cumulative incidence for ischemic stroke (ages 45-59 years: risk ratio = 2.04, 95% confidence interval: 1.55, 2.69; ages 60-74 years: risk ratio = 1.58, 95% confidence interval: 1.31, 1.91; ages >or=75 years: risk ratio = 1.12, 95% confidence interval: 0.94, 1.32). Intracerebral hemorrhage was more common in Mexican Americans (age-adjusted risk ratio = 1.63, 95% confidence interval: 1.24, 2.16). The subarachnoid hemorrhage age-adjusted risk ratio was 1.57 (95% confidence interval: 0.86, 2.89). Mexican Americans experience a substantially greater ischemic stroke and intracerebral hemorrhage incidence compared with non-Hispanic Whites. As the Mexican-American population grows and ages, measures to target this population for stroke prevention are critical.

Ischemic stroke subtypes: a population-based study of incidence rates among blacks and whites

BACKGROUND AND PURPOSE

Blacks have an excess burden of stroke compared with whites; however, data comparing ischemic stroke subtypes among the 2 groups are limited and typically involve relative frequencies. The objective of this study is to compare the incidence rates of ischemic stroke subtypes between blacks and whites within a large, representative, biracial population.

METHODS

The Greater Cincinnati/Northern Kentucky Stroke Study is designed to measure incidence rates and trends of all strokes within a well-defined, large, biracial population. Hospitalized cases were ascertained by International Classification of Disease (9th revision; ICD-9) discharge codes. Out-of-hospital events were ascertained by prospective screening of emergency department admission logs, review of coroners' cases, and monitoring all public health and hospital-based primary care clinics. A sampling scheme was used to ascertain events from nursing homes and all other primary care physician offices. All potential cases underwent detailed chart abstraction and confirmed by physician review. Based on all available clinical, laboratory, and radiographic information, ischemic stroke cases were subtyped into the following categories: cardioembolic, large-vessel, small-vessel, other, and stroke of undetermined cause. Race-specific incidence rates were calculated and compared after adjusting for age and gender, and standardizing to the 1990 US population.

RESULTS

Between July 1, 1993, and June 30, 1994, 1956 first-ever ischemic strokes occurred among blacks and whites in the study population. Small-vessel strokes and strokes of undetermined cause were nearly twice as common among blacks. Large-vessel strokes were 40% more common among blacks than whites, and there was a trend toward cardioembolic strokes being more common among blacks.

CONCLUSIONS

The excess burden of ischemic strokes among blacks compared with whites is not uniformly spread across the different subtypes. Large-vessel strokes are more common and cardioembolic stroke are as common among blacks, traditionally thought to be more common among whites.