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Statistical models used to predict personal risk of death from coronary heart disease (CHD) have been based on studies among white populations. We compared the predictive functions derived from black and white men and women, using the pooled data of 2 national cohorts: the First National Health and Nutrition Examination Survey (NHANES I) Epidemiologic Follow-up Study and the Second National Health and Nutrition Examination Survey (NHANES II) Mortality Study. The participants included 6,937 white men, 940 black men, 9,202 white women, and 1,463 black women aged 30 to 74 years who were free of CHD at baseline. The 2 cohorts were followed for 20 and 15 years, respectively. There were no significant differences between blacks and whites in the magnitude of the Cox coefficients for most of the personal risk factors (i.e., age, systolic blood pressure, serum total cholesterol, smoking, and diabetes mellitus status) for men and women. The receiver operating characteristic (ROC) analyses, with all risk factors considered collectively, suggest that the models have similar ability to rank personal relative risk among blacks and whites. The areas under the ROC curve were 0.77 and 0.76 for white and black men, respectively, and 0.84 and 0.82 for white and black women, respectively. However, the equation derived from white men overestimated the 15-year cumulative CHD mortality in black men by about 60%. Thus, predictive functions derived from 1 demographic group (e.g., whites) can be applied to another subgroup (e.g., blacks) to rank personal risk. However, prediction of absolute risk is less accurate.

In this paper, the authors model the nonmonotonic relation between body mass index (BMI) (weight (kg)/height2 (m2)) and mortality in 13,242 black and white participants in the NHANES I Epidemiologic Follow-up Study in order to estimate the BMI at which minimum mortality occurs. The BMI of minimum mortality was 27.1 for black men (95% confidence interval (CI) 24.8-29.4), 26.8 for black women (95% CI 24.7-28.9), 24.8 for white men (95% CI 23.8-25.9), and 24.3 for white women (95% CI 23.3-25.4). Each confidence interval included the group average. Analyses conducted by smoking status and after exclusion of persons with baseline illness and persons who died during the first 4 years of follow-up led to virtually identical estimates. The authors determined the range of values over which risk of all-cause mortality would increase no more than 20% in comparison with the minimum. This interval was nine BMI units wide, and it included 70% of the population. These results were confirmed by parallel analyses using quantiles. The model used allowed the estimation of parameters in the BMI-mortality relation. The resulting empirical findings from each of four race/sex groups, which are representative of the US population, demonstrate a wide range of BMIs consistent with minimum mortality and do not suggest that the optimal BMI is at the lower end of the distribution for any subgroup.

Body mass index (BMI) is the most commonly used measure of obesity. Recently, some investigators have advocated direct measurement of adiposity rather than use of the BMI. This study was undertaken to determine the ability of BMI to predict body fat levels in three populations of West African heritage living in different environments. A total of 1,054 black men and women were examined in Nigeria, Jamaica, and the United States during 1994 and 1995. A standardized protocol was used to measure height, weight, waist and hip circumferences, and blood pressure at all sites; percentage of body fat was estimated using bioelectrical impedance analysis. Percentage of body fat and BMI were highly correlated within site- and sex-specific groups, and the resulting r2 ranged from 0.61 to 0.85. The relation was quadratic in all groups except Nigerian men, in whom it was linear. The regression coefficients were similar across sites, yet the mean body fat levels differed significantly (p < 0.001) as estimated by the intercept, making intersite comparison difficult. Compared with BMI, percentage of body fat was not a better predictor of blood pressure or waist or hip circumference.

Objectives: This study was undertaken to describe the distribution of blood pressures, hypertension prevalence, and associated risk factors among seven populations of West African origin., Methods: The rates of hypertension in West Africa (Nigeria and Cameroon), the Caribbean (Jamaica, St. Lucia, Barbados), and the United States (metropolitan Chicago, Illinois) were compared on the basis of a highly standardized collaborative protocol. After researchers were given central training in survey methods, population-based samples of 800 to 2500 adults over the age of 25 were examined in seven sites, yielding a total sample of 10014., Results: A consistent gradient of hypertension prevalence was observed, rising from 16% in West Africa to 26% in the Caribbean and 33% in the United States. Mean blood pressures were similar among persons aged 25 to 34, while the increase in hypertension prevalence with age was twice as steep in the United States as in Africa. Environmental factors, most notably obesity and the intake of sodium and potassium, varied consistently with disease prevalence across regions., Conclusion: The findings demonstrate the determining role of social conditions in the evolution of hypertension risk in these populations.

Differences in lipoprotein(a) [Lp(a)] levels across populations have been described and blacks are known to have higher Lp(a) values compared to whites. However, environmental factors which influence Lp(a) levels have been difficult to identify. We took advantage of the large environmental contrast which exists against a common genetic background between U.S. and Nigerian blacks to examine the relationship between Lp(a) and apolipoprotein(a) magnitude of apo(a) isoforms. Although the distribution of Lp(a) and apo(a) isoforms was nearly Gaussian in both populations, mean serum Lp(a) values were significantly higher in the United States than in Nigeria (20.5 vs. 12.7 mg/dl; P = 0.0001) and U.S. blacks had a higher frequency of the large molecular weight isoforms compared to Nigerians. Similar trends in the relationship between apo(a) isoform and Lp(a) concentration were seen in both populations; however, the magnitude of the effect was different. Compared to the Nigerians, U.S. blacks had significantly higher mean Lp(a) values for the same apo(a) isoform. The association of Lp(a) with low density lipoprotein-cholesterol (LDL-C) level was not significant after correcting for the contribution of Lp(a) cholesterol to LDL-C in both populations. Surprisingly, the association between Lp(a) and total-C remained significant (r = 0.20, P = 0.04) after similar correction for the contribution of Lp(a) cholesterol in the U.S. sample. Understanding the relationship between other factors including lifestyle characteristics capable of influencing total-C may help explain the unusually high Lp(a) level observed in this U.S. population.

Comorbidity, the co-existence of multiple chronic conditions in a single individual, has been shown to modify the prognosis of disease states. To estimate disease burdens within and among racial subpopulations of the United States, we examined cross-sectional patterns of comorbidity and their impact on survival using data from the NHANES-1 Epidemiologic Follow-up Study (NHEFS). We considered the occurrence of four cardiovascular conditions: stroke, coronary heart disease, hypertension and diabetes. We summarize the joint occurrence of these four conditions using these different methodologies: the number of conditions occurring in each individual and two summaries that weight the conditions according to their prognostic significance. Using all three methodologies, we found an excess burden of chronic disease in black women as compared with white women. Black men had an excess burden compared to white men for the first two methodologies. However, when we model the relationship of the joint occurrence of the conditions to subsequent mortality, black men and white men are seen to have a similar burden. This similarity of black and white men is due to an interaction between race and prevalent stroke in men that we hypothesize may be due to the small number of black men available for study. Given the apparent conditioning effect of co-existing diseases, it is evident that estimation of disease burdens among groups that differ in terms of health status, in particular among U.S. blacks and whites, requires accounting for the occurrence of multiple chronic diseases. Using either the number of conditions or the prognosis weighted summary, we demonstrated a higher burden of the conditions considered in blacks that in whites in a sample of the U.S. population.

Obesity has been shown to be associated with hypertension in Africa, the Caribbean, and the United States, but there has not previously been an opportunity to compare the magnitude of this relation and estimate the contribution of obesity to hypertension risk across these populations. The International Collaborative Study on Hypertension in Blacks (ICSHIB) used age-stratified sampling and a standardized protocol to measure blood pressure and hypertension risk factors. We analyzed data on 9,102 men and women, age 25-74 years, from seven sites. We studied hypertension (140/90 mmHg or medication) in relation to body mass index (BMI) and sex-specific BMI cut-points designating "overweight" and "obesity." The prevalence of these conditions ranged from 6% to 63% for overweight, from 1% to 36% for obesity, and from 12% to 35% for hypertension. Adjusted relative risks were similar in most sites, ranging from 1.3 to 2.3 for both cut-points. We found that 6-29% of hypertension in each population was attributable to overweight and 0-16% to obesity. Comparing rural Africa with the United States, 43% of the difference in hypertension prevalence for women was attributable to overweight, and 22% for men, whereas respective values for obesity were 14% and 11%. These results indicate that the association between adiposity and hypertension is roughly constant across a range of environments, with little evidence for variation in susceptibility to effects of overweight in these groups.

People of African descent in the Caribbean and the USA originated from the Bight of Benin in West Africa. Although these populations share a common genetic heritage, they now live under different socioeconomical conditions. Assuming genetic similarity, a cross-cultural examination of these peoples in West Africa, the Caribbean and the USA may attenuate the effect of genetic factors and allow the assessment of environmental contributions to a biological outcome. We carried out an epidemiological survey to determine the prevalence of hypertension and the contribution of risk factors to the variation in blood pressure. We measured the height, weight, waist and hip circumferences, and blood pressure of adults in Nigeria, Cameroon, Jamaica, St. Lucia, Barbados and the USA. In urban populations there was a trend towards increasing weight, height, body mass index, and proportions of those overweight and obese going from West Africa to the USA, with the Caribbean being intermediate. The prevalence of hypertension lay on a similar gradient. Given a common genetic susceptibility, urbanization and western acculturation are therefore associated with increasing hypertension and obesity.

A survey of the prevalence of hypertension and associated risk factors including obesity was carried out among persons of West African heritage currently living in societies at different stages of social, economic and technological development. We present here the distribution of several anthropometric variables and the prevalence of obesity in these populations. Using a standard protocol with centralized training of field staff, 7,439 men and women aged 24 to 75 from six multinational sites were recruited and examined. Although men were taller, women were more obese across sites. Body mass index (BMI) and consequently the prevalence of overweight and obesity increased with westernization from rural African subsistence farming communities to suburban Chicago. Average BMI increased with age until about age 54, and then began to decline or at least level off. The mean BMI for African-American men and women was 27.1kg/m2 and 30.8kg/m2, respectively. Men displayed high levels of centripetal fatness, measured as the waist-to-hip ratio (WHR), compared to the women across site. Based on the US Department of Agriculture guidelines, 22.6% and 56.9% of the African-American men and women had elevated WHR. Although account must be taken of the important contribution of an individual's genetic background, this multinational study of persons with similar heritage clearly shows the potent impact of current environmental factors on the distribution and level of obesity.

Objective: To evaluate the effect of echocardiographically determined left ventricular hypertrophy (LVH) on survival in comparison with number of stenosed vessels and left ventricular systolic dysfunction., Design: Cohort study based on a consecutive sample from a hospital registry, with a mean follow-up of 5 years., Setting: An inner-city public hospital in Chicago, Ill., Patients: The study included 1089 consecutive black patients who underwent both coronary angiography and M-mode echocardiography as part of a diagnostic evaluation., Results: Nonstenosed coronary arteries, single-vessel disease, and multivessel disease were found in 48%, 16%, and 36% of patients, respectively; LVH (left ventricular mass index > 131 g/m2 in men and > 100 g/m2 in women) was detected in 50% of patients. Hypertrophy without coexistent obstructive coronary disease was associated with a lower survival rate than that observed for single-vessel disease and was similar to multivessel disease. When LVH, number of diseases vessels, and left ventricular dysfunction were subjected to multivariate analysis, hypertrophy conferred a relative risk (RR) of 2.4 (95% confidence interval [CI], 1.7 to 3.2). By comparison, the presence of a single stenosed vessel did not increase the risk of death. Multivessel disease and ejection fraction less than 45% were associated with an RR of 1.6 (95% CI, 1.1 to 2.2) and 2.0 (95% CI, 1.4 to 2.7), respectively. Calculation of the attributable risk fraction demonstrated that for every 100 deaths in this cohort, LVH independently accounted for 37. The corresponding attributable risk fractions were 1%, 22%, and 9% for single-vessel disease, multivessel disease, and ventricular dysfunction, respectively., Conclusions: Left ventricular hypertrophy was associated with a greater RR and attributable risk than the traditional measures of coronary disease severity. The high prevalence and powerful risk of LVH make an important contribution to the adverse survival rates among black patients with heart disease and may account for much of the black-white differential.

Familial aggregation of cardiovascular diseases and diabetes has been consistently demonstrated. However, virtually all of the evidence on the familial patterns of these diseases has come from white population samples. This study evaluates the level of familial excess risk among first degree relatives of 232 African-American pedigrees which included 1,420 individuals recruited from the Chicago, IL, area. Excess disease risk was observed among relatives (parents and offsprings) of affected probands compared to relatives of unaffected probands for coronary heart disease (odds ratio [OR] = 5.30; 95% confidence interval [CI] = 2.51-11.23); hypertension (OR = 1.98; CI = 1.41-2.80); stroke (OR = 3.24; CI = 1.08-9.70); and diabetes (OR = 2.95; CI = 1.55-5.62). The results of this study clearly show that coronary heart disease, hypertension, stroke, and diabetes aggregate in some African-American families and not others. Unaffected relatives of persons suffering from these diseases should be encouraged to have their blood pressure, lipid, and blood glucose levels measured at frequent intervals. These recommendations are particularly urgent in African-American communities because of the disproportionately high morbidity and mortality experienced from cardiovascular diseases and diabetes.

Over the past two decades, national hypertension-control programs and policies have focused on early diagnosis and management. Measured by intermediate results--such as percentages of cases now taking medication--these efforts have been markedly successful, especially among black hypertensives. The ultimate measure of success--reduction in hypertension-associated disease and death--must address the one-third excess prevalent among blacks. Biologic and age-specific variables in diagnosis and treatment must be accommodated. Future gains in efficient use of resources and equity in outcome will require use of new technologies and models of targeting.