Race differences in estimates of sudden coronary heart disease mortality, 1980-1988: the impact of ill-defined death

Race, common genetic variation, and therapeutic response disparities in heart failure

Because of its comparatively recent evolution, Homo sapiens exhibit relatively little within-species genomic diversity. However, because of genome size, a proportionately small amount of variation creates ample opportunities for both rare mutations that may cause disease as well as more common genetic variations that may be important in disease modification or pharmacogenetics. Primarily because of the East African origin of modern humans, individuals of African ancestry (AA) exhibit greater degrees of genetic diversity than more recently established populations, such as those of European ancestry (EA) or Asian ancestry. Those population effects extend to differences in frequency of common gene variants that may be important in heart failure natural history or therapy. For cell-signaling mechanisms important in heart failure, we review and present new data for genetic variation between AA and EA populations. Data indicate that: 1) neurohormonal signaling mechanisms frequently (16 of the 19 investigated polymorphisms) exhibit racial differences in the allele frequencies of variants comprising key constituents; 2) some of these differences in allele frequency may differentially affect the natural history of heart failure in AA compared with EA individuals; and 3) in many cases, these differences likely play a role in observed racial differences in drug or device response.

Gene-environment interaction between SCN5A-1103Y and hypokalemia influences QT interval prolongation in African Americans: the Jackson Heart Study

BACKGROUND

African-American ancestry, hypokalemia, and QT interval prolongation on the electrocardiogram are all risk factors for sudden cardiac death (SCD), but their interactions remain to be characterized. SCN5A-1103Y is a common missense variant, of African ancestry, of the cardiac sodium channel gene. SCN5A-1103Y is known to interact with QT-prolonging factors to promote ventricular arrhythmias in persons at high risk for SCD, but its clinical impact in the general African-American population has not been established.

METHODS

We genotyped SCN5A-S1103Y in 4,476 participants of the Jackson Heart Study, a population-based cohort of African Americans. We investigated the effect of SCN5A-1103Y, including interaction with hypokalemia, on QT interval prolongation, a widely-used indicator of prolonged myocardial repolarization and predisposition to SCD. We then evaluated the two sub-components of the QT interval: QRS duration and JT interval.

RESULTS

The carrier frequency for SCN5A-1103Y was 15.4%. SCN5A-1103Y was associated with QT interval prolongation (2.7 milliseconds; P < .001) and potentiated the effect of hypokalemia on QT interval prolongation (14.6 milliseconds; P = .02). SCN5A-1103Y had opposing effects on the two sub-components of the QT interval, with shortening of QRS duration (-1.5 milliseconds; P = .001) and prolongation of the JT interval (3.4 milliseconds; P < .001). Hypokalemia was associated with diuretic use (78%; P < .001).

CONCLUSIONS

SCN5A-1103Y potentiates the effect of hypokalemia on prolonging myocardial repolarization in the general African-American population. These findings have clinical implications for modification of QT prolonging factors, such as hypokalemia, in the 15% of African Americans who are carriers of SCN5A-1103Y.

Body mass index, exercise capacity, and mortality risk in male veterans with hypertension

BACKGROUND

Overweight and obesity are associated with increased risk of chronic diseases and mortality. Exercise capacity is inversely associated with mortality risk. However, little is known on the interaction between fitness, fatness, and mortality risk in hypertensive individuals. Thus, we assessed the interaction between exercise capacity, fatness, and all-cause mortality in hypertensive males.

METHODS

A graded exercise test was performed in 4,183 hypertensive veterans (mean age ± s.d.; 63.3 ± 10.5 years) at the Veterans Affairs Medical Center, Washington, DC. We defined three body weight categories based on body mass index (BMI): normal weight (BMI <25); overweight (BMI 25-29.9); and obese (BMI ≥30); and three fitness categories based on peak metabolic equivalents (METs) achieved: low-fit (≤5 METs); moderate-fit (5.1-7.5 MET); and high-fit (>7.5 METs).

RESULTS

During a median follow-up period of 7.2 years, there were 1,000 deaths. The association between exercise capacity and mortality risk was strong, inverse, and graded. For each 1-MET increase in exercise capacity the adjusted risk was 20% for normal weight, 12% for overweight, and 25% for obese (P < 0.001). When compared to normal weight but unfit individuals, mortality risks were 60% lower in the overweight/high-fit and 78% lower in the obese/high-fit individuals (P < 0.001).

CONCLUSIONS

Increased exercise capacity is associated with lower mortality risk in hypertensive males regardless of BMI. The risk for overweight and obese but fit individuals was significantly lower when compared to normal weight but unfit. These findings suggest that in older hypertensive men, it may be healthier to be fit regardless of standard BMI category than unfit and normal weight.

Spatial clustering of non-transported cardiac decedents: the results of a point pattern analysis and an inquiry into social environmental correlates

Background

People who die from heart disease at home before any attempt at transport has been made may represent missed opportunities for life-saving medical intervention. In this study, we undertook a point-pattern spatial analysis of heart disease deaths occurring before transport in a large metropolitan area to determine whether there was spatial clustering of non-transported decedents and whether there were significant differences between the clusters of non-transported cardiac decedents and the clusters of transported cardiac decedents in terms of average travel distances to nearest hospital and area socioeconomic characteristics. These analyses were adjusted for individual predictors of transport status.

Methods

We obtained transport status from the place of death variable on the death certificate. We geocoded heart disease decedents to residential street addresses using a rigorous, multistep process with 97% success. Our final study population consisted of 11,485 adults aged 25-74 years who resided in a large metropolitan area in west-central Florida and died from heart disease during 1998-2002. We conducted a kernel density analysis to identify clusters of the residential locations of cardiac decedents where there was a statistically significant excess probability of being either transported or not transported prior to death; we controlled for individual-level covariates using logistic regression-derived probability estimates.

Results

The majority of heart disease decedents were married (53.4%), male (66.4%), white (85.6%), and aged 65-74 years at the time of death (54.7%), and a slight majority were transported prior to death (57.7%). After adjustment for individual predictors, 21 geographic clusters of non-transported heart disease decedents were observed. Contrary to our hypothesis, clusters of non-transported decedents were slightly closer to hospitals than clusters of transported decedents. The social environmental characteristics of clusters varied in the expected direction, with lower socioeconomic and household resources in the clusters of non-transported heart disease deaths.

Conclusions

These results suggest that in this large metropolitan area unfavorable household and neighborhood resources played a larger role than distance to hospital with regard to transport status of cardiac patients; more research is needed in different geographic areas of the United States and in other industrialized nations.

Using vital statistics to estimate the population-level impact of osteoporotic fractures on mortality based on death certificates, with an application to France (2000-2004)

Background

We developed a methodology using vital statistics to estimate the impact of osteoporotic fractures on the mortality of an entire population, and applied it to France for the period 2000-2004.

Methods

Current definitions of osteoporotic fractures were reviewed and their components identified. We used the International Classification of Diseases with national vital statistics data for the French adult population and performed cross-classifications between various components: age, sex, I-code (site) and E-code (mechanism of fracture). This methodology allowed identification of appropriate thresholds and categorization for each pertinent component.

Results

2,625,743 death certificates were analyzed, 2.2% of which carried a mention of fracture. Hip fractures represented 55% of all deaths from fracture. Both sexes showed a similar pattern of mortality rates for all fracture sites, the rate increased with age from the age of 70 years. The E-high-energy code (present in 12% of death certificates with fractures) was found to be useful to rule-out non-osteoporotic fractures, and to correct the overestimation of mortality rates. Using this methodology, the crude number of deaths associated with fractures was estimated to be 57,753 and the number associated with osteoporotic fractures 46,849 (1.85% and 1.78% of all deaths, respectively).

Conclusion

Osteoporotic fractures have a significant impact on overall population mortality.

Clinical correlates and heritability of QT interval duration in blacks: the Jackson Heart Study

BACKGROUND

Electrocardiographic QT interval prolongation is a risk factor for sudden cardiac death and drug-induced arrhythmia. The clinical correlates and heritability of QT interval duration in blacks have not been well studied despite their higher risk for sudden cardiac death compared with non-Hispanic whites. We sought to investigate potential correlates of the QT interval and estimate its heritability in the Jackson Heart Study.

METHODS AND RESULTS

The Jackson Heart Study comprises a sample of blacks residing in Jackson, Miss, of whom 5302 individuals with data at the baseline examination were available for study. Jackson Heart Study participants on QT-altering medications, with bundle-branch block, paced rhythm, atrial fibrillation/flutter, or other arrhythmias were excluded, resulting in a sample of 4660 individuals eligible for analyses. The relation between QT and potential covariates was tested using multivariable stepwise linear regression. Heritability was estimated using Sequential Oligogenic Linkage Analysis Routine in a subset of 1297 Jackson Heart Study participants in 292 families; the remaining sample included unrelated individuals. In stepwise multivariable linear regression analysis, covariates significantly associated with QT interval duration included R-R interval, sex, QRS duration, age, serum potassium, hypertension, body mass index, coronary heart disease, diuretic use, and Sokolow-Lyon voltage (P < or = 0.01 for all). The heritability of QT interval duration in the age-, sex-, and R-R interval-adjusted model and in the fully adjusted model was 0.41 (SE, 0.07) and 0.40 (SE, 0.07; P < 10(-11) for both), respectively.

CONCLUSIONS

There is substantial heritability of adjusted QT interval in blacks, supporting the need for further investigation to identify its genetic determinants.

Neighborhood income, health insurance, and prehospital delay for myocardial infarction: the atherosclerosis risk in communities study

BACKGROUND

Outcomes following an acute myocardial infarction (AMI) are generally more favorable if prehospital delay time is minimized.

METHODS

We examined the association of neighborhood household income (nINC) and health insurance status with prehospital delay among a weighted sample of 9700 men and women with a validated, definite, or probable AMI in the Atherosclerosis Risk in Communities (ARIC) community surveillance study (1993-2002). Weighted multinomial regression with generalized estimation equations was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) and to account for the clustering of patients within census tracts.

RESULTS

Low nINC was associated with a higher odds of long vs short delay (OR, 1.46; 95% CI, 1.09-1.96) and medium vs short delay (OR, 1.43; 95% CI, 1.12-1.81) compared with high nINC in a model including age, sex, race, diabetes, hypertension, presence of chest pain, arrival at the hospital via emergency medical service, distance from residence to hospital, study community, and year of AMI event. Meanwhile, compared with patients with prepaid insurance or prepaid plus Medicare, patients with Medicaid were more likely to have a long vs short delay (OR, 1.87; 95% CI, 1.10-3.19) and a medium vs short delay (OR, 1.76; 95% CI, 1.13-2.74).

CONCLUSIONS

Both low nINC and being a Medicaid recipient are associated with longer prehospital delay. Reducing socioeconomic and insurance disparities in prehospital delay is critical because excess delay time may hinder effective care for AMI.

Exercise capacity and mortality in black and white men

BACKGROUND

Exercise capacity is inversely related to mortality risk in healthy individuals and those with cardiovascular diseases. This evidence is based largely on white populations, with little information available for blacks.

METHODS AND RESULTS

We assessed the association between exercise capacity and mortality in black (n=6749; age, 58+/-11 years) and white (n=8911; age, 60+/-11 years) male veterans with and without cardiovascular disease who successfully completed a treadmill exercise test at the Veterans Affairs Medical Centers in Washington, DC, and Palo Alto, Calif. Fitness categories were based on peak metabolic equivalents (METs) achieved. Subjects were followed up for all-cause mortality for 7.5+/-5.3 years. Among clinical and exercise test variables, exercise capacity was the strongest predictor of risk for mortality. The adjusted risk was reduced by 13% for every 1-MET increase in exercise capacity (hazard ratio, 0.87; 95% confidence interval, 0.86 to 0.88; P<0.001). Compared with those who achieved <5 METs, the mortality risk was approximately 50% lower for those with an exercise capacity of 7.1 to 10 METs (hazard ratio, 0.51; 95% confidence interval, 0.47 to 0.56; P<0.001) and 70% lower for those achieving >10 METs (hazard ratio, 0.31; 95% confidence interval, 0.26 to 0.36; P<0.001). The findings were similar for those with and without cardiovascular disease and for both races.

CONCLUSIONS

Exercise capacity is a strong predictor of all-cause mortality in blacks and whites. The relationship was inverse and graded, with a similar impact on mortality outcomes for both blacks and whites.

Social and demographic predictors of no transport prior to premature cardiac death: United States 1999-2000

BACKGROUND

In the United States, over one-third of premature cardiac deaths occur outside of a hospital, without any transport prior to death. Transport prior to death is a strong, valid indicator of help-seeking behavior. We used national vital statistics data to examine social and demographic predictors of risk of no transport prior to cardiac death. We hypothesized that persons of lower social class, immigrants, non-metropolitan residents, racial/ethnic minorities, men, and younger decedents would be more likely to die prior to transport.

METHODS

Our study population consisted of adult residents of the United States, aged 25 to 64 years, who died from heart disease during 1999-2000 (n = 242,406). We obtained transport status from the place of death variable on the death certificate. The independent effects of social and demographic predictor variables on the risk of a cardiac victim dying prior to transport vs. the risk of dying during or after transport to hospital were modeled using logistic regression.

RESULTS

Results contradicted most of our a priori hypotheses. Persons of lower social class, immigrants, most non-metropolitan residents, and racial/ethnic minorities were all at lower risk of dying prior to transport. The greatest protective effect was found for racial/ethnic minority decedents compared with whites. The strongest adverse effect was found for marital status: the risk of dying with no transport was more than twice as high for those who were single (OR 2.35; 95% CI 2.29-2.40) or divorced (OR 2.29; 95% CI 2.24-2.34), compared with married decedents. Geographically, residents of the Western United States were at a 47% increased risk of dying prior to transport compared with residents of the metropolitan South.

CONCLUSION

Our results suggest that marital status, a broad marker of household structure, social networks, and social support, is more important than social class or race/ethnicity as a predictor of access to emergency medical services for persons who suffer an acute cardiac event. Future research should focus on ascertaining "event histories" for all acute cardiac events that occur in a community, with the goal of identifying the residents most susceptible to cardiac fatalities prior to medical intervention and transport.

No racial differences in mortality found among veterans health administration out-patients

OBJECTIVE

Health care delivery systems that offer equal access to ambulatory care may hold promise for preventing and correcting racial disparities that exist in our health care system as a whole. We examined whether racial differences in mortality rates exist among patients receiving outpatient care within the Veterans Health Administration.

STUDY DESIGN AND SETTING

This study used data from the 1998 National Survey of Ambulatory Care Patients, a prospective monitoring system of patient outcomes. We used an outpatient care system in the Veterans Health Administration. We followed 25,172 Whites and 3,517 African-Americans for 48 months. The main study outcome measures were unadjusted and adjusted mortality rates over a 48-month period.

RESULTS

African-Americans had significantly lower unadjusted 48-month mortality rates than Whites (33 vs. 40 deaths per 1,000 person-year, hazard ratio, 0.84; 95% confidence interval [CI], 0.75-0.95). After risk adjustment, the mortality rates became similar for African-Americans and Whites (hazard ratio, 0.99; 95% CI, 0.89-1.09). These findings were consistent across all time points evaluated during the 48-month follow-up.

CONCLUSIONS

The lack of racial differences in mortality in patients receiving ambulatory care in the Veterans Health Administration is reassuring, given the emphasis on equal access within this health care system. This warrants further research to determine whether efforts to improve access in other settings have the potential to reduce racial disparities in health care.

Urinary antispasmodic use and the risks of ventricular arrhythmia and sudden death in older patients

OBJECTIVES

The introduction of new medications to treat overactive bladder has resulted in a significant increase in the number of individuals with this condition who use medications for symptoms. Formal epidemiological studies of the safety of these medications in typical patient populations are lacking, particularly studies of serious events. We sought to determine whether the use of urinary antispasmodics increases the risk of ventricular arrhythmias or sudden death.

DESIGN

Retrospective cohort study.

SETTING

Retrospective analysis of data of participants in community, hospital or nursing home setting.

PARTICIPANTS

Fourteen thousand six hundred thirty-eight subjects with a diagnosis of urinary incontinence made between January 1, 1991, and June 30, 1995; all were aged 65 and older and enrolled in Medicare and Medicaid or the Pharmacy Assistance for the Aged and Disabled programs of New Jersey.

MEASUREMENTS

Filled prescriptions for oxybutynin (Ditropan), flavoxate (Urispas), hyoscyamine (Cystospas), and hyoscyamine sulfate (Cystospas-M) were used to define days of exposure to these drugs. We also identified all use of nonsedating antihistamines and cytochrome P450 3A4 inhibitors, and their concurrent use, to serve as a positive control exposure. Two outcomes were then defined: a new diagnosis of ventricular arrhythmia combined with initiation of an antiarrhythmic medication and sudden death. Other covariates, including clinical, demographic, medication use, and healthcare utilization variables, were also assessed. Adjusted risk ratios of ventricular arrhythmia and sudden death were derived from multivariable Cox proportional hazards models.

RESULTS

There was no significant association between periods of use of urinary antispasmodics and the development of ventricular arrhythmias (adjusted risk ratio (RR) = 1.23, 95 confidence interval (CI) = 0.87-1.75) or sudden death (adjusted RR = 0.70, 95% CI = 0.28-1.74). A significantly increased risk of ventricular arrhythmia was observed for the positive control regimen, concurrent use of nonsedating antihistamines and cytochrome P450 3A4 inhibitors (adjusted RR = 5.47; 95% CI = 1.34-22.26), but not for use of either drug group alone. Concurrent use of nonsedating antihistamines and cytochrome P450 3A4 inhibitors was also associated with a significant increase in the risk of sudden death (adjusted RR = 21.50, 95% CI = 5.23-88.37). Other variables significantly associated with ventricular arrhythmia included ischemic heart disease and congestive heart failure, whereas nursing home use before the index date was associated with a decreased likelihood of receiving a diagnosis of and treatment for ventricular arrhythmia. Other variables significantly associated with sudden death included male gender, black race, and congestive heart failure.

CONCLUSIONS

Antimuscarinic urinary antispasmodics available before 1996 were not associated with an increased risk of ventricular arrhythmias and sudden death. Additional study will be required to confirm these results, exclude the possibility of unmeasured confounders contributing to any lack of an observed relationship, and extend these findings to newer agents such as tolterodine.

Community-wide coronary heart disease mortality in Mexican Americans equals or exceeds that in non-Hispanic whites: the Corpus Christi Heart Project

PURPOSE

Previous comparisons of coronary heart disease mortality between Mexican Americans and non-Hispanic whites have given paradoxic results: despite their adverse cardiovascular risk profiles, especially a greater prevalence of diabetes, Mexican Americans are reported to have lower rates of mortality from coronary heart disease.

SUBJECTS AND METHODS

We performed a community-based surveillance among all residents of Nueces County, Texas, aged 25 to 74 years, from 1990 to 1994. All death certificates were obtained and coded, and deaths potentially related to coronary heart disease were selected and validated by standardized methods blinded to ethnicity. Validated in-hospital and out-of-hospital coronary heart disease mortality was compared between 785 Mexican Americans and 862 non-Hispanic white women and men.

RESULTS

Validated coronary heart disease mortality in Mexican Americans exceeded that for non-Hispanic whites in the same community. Among women, definite coronary heart disease mortality was 40% greater among Mexican Americans (rate ratio [RR] 1.43, 95% confidence interval [CI]: 1.12 to 1.82), as was all coronary heart disease mortality (RR, 1.32, 95% CI: 1.08 to 1.63). Among men, Mexican Americans had greater rates of all (RR, 1.11; 95% CI: 0.96 to 1.28) and definite coronary heart disease mortality (RR, 1.16; 95% CI: 0.91 to 1.47), but the associations were not statistically significant.

CONCLUSIONS

When community-wide mortality rates from coronary heart disease are properly validated, Mexican Americans have rates equal to or higher than those of non-Hispanic whites. Community-based surveillance with validation of coronary heart disease as the cause of death is necessary to avoid the errors that occur with the use of death certificates alone.

Definition of race and ethnicity in older people in Medicare and Medicaid

BACKGROUND

Race and ethnicity are important predictors of health care access and outcomes, but quality of their documentation in the healthcare system is often problematic.

OBJECTIVES

To study the agreement between Medicare and Medicaid descriptions of race and ethnicity in older beneficiaries.

DESIGN

Quasiexperimental design in a natural practice setting.

SETTING

New Jersey.

PARTICIPANTS

153,241 dually enrolled participants in Medicare and Medicaid.

MEASUREMENTS

Agreement rates between administrative databases on recipients' race and ethnicity.

RESULTS

Agreement between Medicare and Medicaid on the recipients' race and ethnicity was modest (kappa = .58; 95% CI, .57-.58) for men and women alike and across different age groups. Depending on whether Medicare or Medicaid was used as the reference standard, the relative agreement rates for race and ethnic group assignments varied. For example, using Medicare as the reference, the relative agreement rate was 84% for whites, 74% for blacks, 61% for others, 23% for Hispanics, and only 5% for Asians. Using Medicaid as the reference, a different pattern emerged. However, such gradients of agreement rates across racial groups were observed in both programs. Medicare and Medicaid reported different percentages of all race and ethnicity groups, with Medicaid reporting greater proportions of White and Black beneficiaries, and Medicare reporting greater proportions of Hispanic, Asian, and Other groups.

CONCLUSIONS

Depiction of race and ethnicity data in large government health insurance programs is approximate at best and often contradictory from one program to another. This can impede efforts to study the relationship between these important characteristics and health care utilization and outcomes.