Association of waist circumference with ApoB to ApoAI ratio in black and white Americans

BACKGROUND

Although numerous studies have demonstrated obesity as an aspect of the insulin resistance syndrome in cardiovascular disease (CVD), the mechanism is not clear. Central adiposity, acting through many CVD risk factors, including, plasma glucose, insulin, total cholesterol, low density lipoprotein-cholesterol (LDL-C) and lipoprotein moities-apolipoprotein B (ApoB), apolipoprotein A-I (ApoAI), by atherogenic and thrombotic mechanisms has been proposed as a possible mechanism. In this study, we examined the relationship between central fat distribution (defined by waist circumference) and the ratio of these lipoproteins (ApoB/ApoAI).

SUBJECTS AND METHODS

Association between ApoB/ApoAI ratio and waist circumference was compared in Blacks (n = 854) and Whites (n = 2552) using the NHANES III population-based samples. Correlation analyses and multiple regression analyses were used to determine the association between ApoB/ApoAI and waist circumference, controlling for age, body mass index (BMI), race, gender, plasma glucose, insulin, serum triglyceride and total cholesterol.

RESULTS

Adjusting for age, ApoB/ApoAI was significantly correlated with waist circumference (Black men: r = 0.38, White men: r = 0.26, Black women: r = 0.20, White women: r = 0.36) (all P < 0.01). Adjusting for age and triglyceride or insulin, waist circumference was also positively correlated with CVD risk factors including, ApoB, LDL-C, plasma glucose and fasting insulin, and inversely correlated with ApoAI and HDL-C in Blacks and Whites (P < 0.05). Overall, triglyceride and total cholesterol were the strongest predictors of ApoB/ApoAI in Blacks and Whites adjusting for age, BMI and insulin, than waist girth (P < 0.01).

CONCLUSIONS

The result of this study suggests the need to investigate ApoB/ApoAI as another possible facet in the insulin resistant syndrome.

Socioeconomic status and morbidity in the last years of life

OBJECTIVES

This study evaluated the effect of socioeconomic status, as characterized by level of education, on morbidity and disability in the last years of life.

METHODS

The analysis used data from the National Health Interview Survey (1986-1990), with mortality follow-up through December 1991.

RESULTS

Among 10,932 decedents 50 years or older at baseline interview, educational attainment was inversely associated with long-term limitation of activity, number of chronic conditions, number of bed days, and days of short hospital stay during the year preceding the interview.

CONCLUSIONS

Decedents with higher socioeconomic status experienced lower morbidity and disability and better quality of life even in their last years of life.

Maximum-likelihood generalized heritability estimate for blood pressure in Nigerian families

Elevated blood pressure (BP) is more common in relatives of hypertensives than in relatives of normotensives, indicating familial resemblance of the BP phenotypes. Most published studies have been conducted in westernized societies. To assess the ability to generalize these estimates, we examined familial patterns of BP in a population-based sample of 510 nuclear families, including 1552 individuals (320 fathers, 370 mothers, 475 sons, and 387 daughters) from Ibadan, Nigeria. The prevalence of obesity in this community is low (body mass index: fathers, 21.6; mothers, 23.6; sons, 19.2; and daughters=21.0 kg/m2). The BP phenotype used in all analyses was created from the best regression model by standardizing the age-adjusted systolic blood pressure (SBP) and diastolic blood pressure (DBP) to 0 mean and unit variance. Heritability was estimated by use of the computer program SEGPATH from the most parsimonious model of "no spouse and neither gender nor generation difference" as 45% for SBP and 43% for DBP. The lack of a significant spouse correlation is consistent with little or no influence of the common familial environment. However, the heritability estimate of <50% for both SBP and DBPs reinforces the importance of the nonshared environmental effect.

Self-reported health status and mortality in a multiethnic US cohort

The authors examined the relation between self-reported health status and mortality among the following racial/ethnic groups: Native Americans, Asian/Pacific Islanders, blacks, whites, and Hispanics. They pooled 1986-1994 data from the National Health Interview Survey to obtain information on more than 700,000 cohort participants. Although fewer than 5,000 Native Americans are included in this cohort, the data provide information previously unavailable for this group. Also included are almost 17,000 Asian/Pacific Islanders, over 90,000 blacks, and over 50,000 Hispanics. The authors found strong associations between self-reported health status and both socioeconomic status and subsequent mortality. A self-report of fair or poor health was associated with at least a twofold increased risk of mortality for all racial/ethnic groups. Even after adjustment for socioeconomic status and measures of comorbidity, a significant relation was found between self-reported health status and subsequent mortality. The authors found that self-reported health status is a strong prognostic indicator for subsequent mortality for both genders and all racial/ethnic groups examined. These results emphasize the utility of using simple filter questions in population research.

Association of waist circumference with risk of hypertension and type 2 diabetes in Nigerians, Jamaicans, and African-Americans

OBJECTIVE

Prior studies have supported that waist circumference correlates better with visceral adipose tissue and is a better predictor of cardiovascular disease than are BMI and waist-to-hip ratio. In this study, we reexamine the role of waist size on the risk of hypertension and type 2 diabetes in African-origin populations from three contrasting environments.

RESEARCH DESIGN AND METHODS

A cross-sectional survey was conducted of 5,042 men and women 25-74 years of age from Nigeria, Jamaica, and the U.S. The relationship between waist, blood pressure, and fasting blood glucose was assessed using multiple linear regression analyses. Logistic regression analyses using sex-specific empirical waist cut-points were used to determine the risks of hypertension and type 2 diabetes.

RESULTS

Waist circumference was positively correlated with blood pressure and fasting blood glucose (P < 0.05). Increasing waist quartiles were significantly associated with higher risks of hypertension in the three populations, as estimated from age-adjusted odds ratios obtained from sex-specific logistic regression models. A highly elevated risk of type 2 diabetes-10-fold for Jamaican men and 23-fold for African-American women-was observed in the comparison of lowest to highest quartiles of waist circumference.

CONCLUSIONS

Substantial reduction in hypertension and diabetes in men and women is achievable if the waist size is decreased in these populations. Intervention programs designed to reduce waist circumference through lifestyle modification, including exercise and diet, may have significant public health significance in reducing the incidence of hypertension and adult-onset diabetes in these populations.

Weight-height relationships among eight populations of West African origin: the case against constant BMI standards

OBJECTIVE

To ascertain whether constant body mass index (BMI) standards are appropriate in genetically similar populations.

DESIGN

Data are taken from the International Collaborative Study of Hypertension in Blacks (ICSHIB), an observational study.

SUBJECTS

Individuals of African descent who were included in ICSHIB. Subjects lived in eight different sites: Barbados; Cameroon (urban and rural); Jamaica; Manchester, UK; Maywood, IL; urban Nigeria; and St Lucia.

MEASUREMENTS

Weight and height.

RESULTS

Constant BMI standards effectively argue for the constancy of slope of the linear regression equations of In(weight) on In(height) across populations. Linear regression results indicate that the height/weight relationship implied by the use of constant BMI standards, is not found in these populations and that there is much variation across groups.

CONCLUSION

The use of constant BMI standards in classifying individuals prognostically may be unwise, even in genetically similar populations.

The influence of cigarette smoking on the association between body weight and mortality. The Framingham Heart Study revisited

PURPOSE

To calculate for two measures of obesity, the Metropolitan Relative Weight (MRW) and body mass index (BMI), the value at which minimum mortality occurs. This was done to retest the hypothesis, in the Framingham Heart Study data, that the association between obesity and mortality can be obscured by an interaction between the measure of obesity and smoking. In the original analysis of the Framingham data it was suggested that there was a U- or J-shaped relationship between MRW and death in smokers but a linear relationship in nonsmokers. The design and setting were those of the NHLBI Framingham Heart Study.

METHODS

The 5209 members of the Framingham Heart Study underwent a baseline examination in 1948-1952 (Exam 1) and they were reexamined at approximately two-year intervals over a 30-year period. The study included both men (n = 2336) and women (n = 2873) in the age range of 28 to 62 years. After excluding persons with missing baseline data, the analytic sample size was 5163. Additional analyses were conducted by deleting persons with cardiovascular disease (CVD) at baseline (n = 135), the sample used by the original paper by Garrison and colleagues, and persons who died within the first four years of follow-up (n = 62). The main outcome measures consisted of thirty-year survival through Exam 16, approximately in 1980, as influenced by MRW or BMI, age, and smoking status at baseline (Exam 1).

RESULTS

We were able to show that the sample sizes of male nonsmokers were too small to test the hypothesis within age groups < 40 and 40-49 years. In men ages 50-62 there was a significant age-adjusted quadratic relationship between BMI or MRW, and risk of death. The estimated BMI at the minimum risk of death for smokers (24.5) and nonsmokers (23.8) were not statistically different. Identical results were found for MRW (minimum: smokers = 112.5, nonsmokers = 111.4). In men and women ages 28-62 there appeared to be a u- or j-shaped relationship between the 30-year crude mortality rate and MRW. After excluding persons with missing data, CVD at baseline, and persons who died within the first four years of follow-up, the age adjusted estimated BMI value at the minimum risk of death was nearly identical for men and women and for smokers and nonsmokers (Men: smokers = 22.8, nonsmokers = 22.8; Women: smokers = 22.9, nonsmokers = 23.3). Additionally, the estimates of the minimum were always below the mean. Identical results were found without deleting persons with CVD at baseline and deaths in the first four years of follow-up. Identical results were found for MRW.

CONCLUSIONS

Reanalysis of the Framingham Heart Study data does not support the hypothesis that there is an interaction between smoking and measures of obesity. Moreover, the estimated BMI or MRW at the minimum risk of death was similar for men and women smokers and nonsmokers alike even after deleting prevalent cases of CVD and deaths within the first four years of follow-up.

Influence of left ventricular geometric patterns on prognosis in patients with or without coronary artery disease

OBJECTIVES

We sought to examine patterns of left ventricular (LV) geometry as determined by echocardiography and their association with mortality in patients with or without coronary artery disease (CAD).

BACKGROUND

The independent prognostic role of LV geometry remains uncertain.

METHODS

We performed a cohort study based on 988 consecutive patients who underwent both coronary arteriography for presumed CAD and echocardiography and were followed up for a mean of 9 years (range 5 to 13). Patients were classified into four LV geometry patterns: normal, concentric remodeling, eccentric LV hypertrophy (LVH) and concentric LVH.

RESULTS

Patients with concentric LVH consistently showed the largest increase in LV posterior wall and septal thickness and LV mass index, as well as relative wall thickness (RWT), regardless of status of the coronary arteries. This pattern conferred the highest risk of both all-cause and cardiac mortality. Eccentric LVH moderately increased the risk of death compared with normal geometry; no substantial increase in mortality was noted in patients with concentric remodeling. When LV index and RWT were analyzed as continuous measures and considered in the same Cox proportional hazards model, increases in LV mass were independently associated with risk, but this outcome was less clear for RWT.

CONCLUSIONS

In this series of patients referred to coronary angiography for suspected CAD, LVH conferred most of the predictive information from echocardiography. Patients with both LVH and abnormal RWT--concentric LVH--represent a group with the greatest mortality risk. Concentric remodeling may not be associated with increased risk of death because the predictive value of RWT is not as strong as for LV mass.

Mortality and optimal body mass index in a sample of the US population

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.

Leptin and body composition of Nigerians, Jamaicans, and US blacks

The role of leptin in humans remains controversial. Leptin concentrations are highly correlated with body fat stores. We tested whether or not this relation was consistent across the range of body composition encompassing the lean as well as the obese. Individuals participating in community-based comparative research in Nigeria (n = 363), Jamaica (n = 372), and the United States (Maywood, IL; n = 699) had their plasma leptin concentrations and body compositions (with bioelectrical impedance analysis) measured. All participants identified themselves as being black. Body mass index (in kg/m2) ranged from 14 to 62. Large differences in mean plasma leptin were noted across populations for both men and women in Nigeria, Jamaica, and the United States, respectively (men: 2.8, 3.9, and 6.8 microg/L; women: 10.3, 18.6, and 27.7 microg/L). An exponential function fit the relation between percentage body fat or total fat mass and leptin for men and women at each site. For women and men the exponential function with either percentage body fat or total fat mass was of the same shape, but increased by a constant in women, yielding higher leptin concentrations than in men at every level of body fat. On the basis of this broad distribution of body composition, the data suggest an exponential response of leptin to increases in body fat stores, consistent with the development of leptin resistance in individuals developing obesity. These findings likewise confirm that men and women exhibit different set points in terms of leptin production.

The relation between income and mortality in U.S. blacks and whites

Differential mortality exists in the United States both between racial/ethnic groups and along gradients of socioeconomic status. The specification of statistical models for processes underlying these observed disparities has been hindered by the fact that social and economic quantities are distributed in a highly nonrandom manner throughout the population. We sought to provide a substantive foundation for model development by representing the shape of the income-mortality relation by racial/ethnic group. We used data on black and white men and women from the longitudinal component of the National Health Interview Survey (NHIS), 1986-1990, which provided 1,191,824 person-years of follow-up and 12,165 mortal events. To account for family size when considering income, we used the ratio of annual family income to the federal poverty line for a family of similar composition. To avoid unnecessary categorizations and prior assumptions about model form, we employed kernel smoothing techniques and calculated the continuous mortality surface across dimensions of adjusted income and age for each of the gender and racial/ethnic groups. Representing regions of equal mortality density with contour plots, we observed interactions that need to be accommodated by any subsequent statistical models. We propose two general theories that provide a foundation for more elaborate and testable hypotheses in the future.

Hypertension in Cuba: evidence of a narrow black-white difference

The Caribbean nation of Cuba is comprised of over 10 million persons who trace their ancestry primarily to Africa and Spain. To date, little data on blood pressure (BP) or hypertension prevalence from Cuba have appeared in English language journals. Because the current government has pursued an active policy of reducing social differentiation on the basis of ethnic origin, Cuba provides an important population laboratory from which to advance the understanding of black-white differences in BP and hypertension. The authors conducted a population-based random sample among adults (aged > 15 years) in the city of Cienfuegos. Overall response rate was 95%, yielding 1633 participants who provided BP readings, self-reported racial group, demographic information, and treatment status. Overall prevalence of hypertension (SBP > or = 140 mm Hg or DBP > or = 90 mm Hg or currently treated) was 44% (46% among blacks and 43% whites; P = 0.19). Excess BP among black subjects was reduced slightly by excluding those under treatment, but attained statistical significance after adjustment for sex and age (P = 0.01). The black-white difference was small, however, relative to that observed in the United States. Racial differences in treatment status and control were also observed. Although there remains a difference in socioeconomic profile between those of African and of European origin in Cuba, this has decreased over recent decades. In the United States, the greater magnitude of social differentiation parallels a greater relative risk of BP elevation among blacks, suggesting that social, economic and psychological factors may play an important role in the observed racial gap in cardiovascular risk.

Mortality patterns among adult Hispanics: findings from the NHIS, 1986 to 1990

OBJECTIVES

The purpose of this study was to assess the mortality pattern of the adult Hispanic population in the United States.

METHODS

This was a cohort study using data from the National Health Interview Survey from 1986 through 1990. Deaths were ascertained by matching the National Death Index through 1991.

RESULTS

This representative national sample included 297,640 non-Hispanic Whites, 53,552 Blacks, and 27,239 Hispanics, all aged 18 years or older at baseline. Different matching criteria resulted in modest differential estimates of the number of deaths by ethnic groups; these differences were quantitatively more important for Hispanics. Overall age-standardized mortality was lower among Hispanics. A prominent age by race interaction was apparent. The Hispanic: White mortality ratio was 1.33, 0.92, and 0.76 among men aged 18 through 44, 45 through 64, and 65 and older, respectively. Among women in the same age groups the Hispanic: White mortality ratio was 1.22, 0.75, and 0.70, respectively.

CONCLUSIONS

Longitudinal cohorts provide an important source of health status information on Hispanics. These results suggest that overall mortality is lower among Hispanics than among non-Hispanic Whites, especially in the oldest age group. Among younger and middle-aged persons, the mortality of Hispanics is similar to or even higher than that of Whites.

Emergence of Western diseases in the tropical world: the experience with chronic cardiovascular diseases

Our knowledge of the disease burden components of tropical populations is fragmentary. Historically, the infectious diseases have been emphasized but, as some populations have undergone socio-economic changes, vital statistics have described a change in the pattern of disease. The picture is of a decline in infectious and a rise in chronic non-communicable disease. We focus here on the emergence of chronic cardiovascular diseases, and use hypertension as the paradigmic example. Early blood pressure surveys showed a virtual absence of hypertension among rural Africans and moderate prevalences in the Caribbean. Prevalence was highest among US and UK blacks. In a recent comparative study of blood pressure and its determinants in Nigeria, Jamaica and the US there was a steep gradient in prevalence from 15% through 26% to 33%. Body mass index and salt intake were the major determinants, accounting for 70% of the variance in hypertension prevalence. Additional information on mechanism comes from the exploration of the renin-angiotensin system across these populations. Angiotensinogen levels rise steadily from Africa to the US and are modestly associated with body mass index (BMI), and even more modestly with polymorphisms of the angiotensinogen gene. 30% of the variation in angiotensin-converting enzyme levels is attributable to the insertion/deletion polymorphism, and angiotensin-converting enzyme levels are modestly related to BMI and blood pressure. Thus, the steep gradient in prevalence is not attributable to the genetics as manifested in the renin-angiotensin system. The usefulness of these and other data on cardiovascular diseases include planning for primordial prevention in Africa and amelioration of existing epidemics in the Caribbean, the US and the UK. Additional long term surveillance data to define the burden and distribution of causes are necessary in Africa. Lastly, education and advocacy to transfer the information to policy makers and planners is required.

Leptin concentration in women is influenced by regional distribution of adipose tissue

Leptin concentrations in humans are increased with obesity, and women have higher leptin concentrations than men. This sex difference reflects the greater fat mass of women. However, there is evidence that factors other than the size of the adipose tissue mass contribute to serum leptin concentrations. This study was undertaken to determine whether anthropometric factors influenced leptin concentrations in our population. Leptin concentrations were measured in 375 persons from a population study of hypertension and diabetes for whom body-composition data (bio-electrical impedance analysis and anthropometry) were available. Serum leptin concentrations were more than four times higher in women than in men (18.5 +/- 13.9 compared with 3.8 +/- 3.6 ng/L, P < 0.0001). In individuals with comparable body mass indexes, these differences persisted after adjustment for either percentage fat (P < 0.05) or fat mass (P < 0.0001) by multivariate-regression analysis. After fat mass was adjusted for, the serum leptin concentration in both men and women was independent of waist circumference but in women was associated with hip circumference. Hip circumference is a proxy measure of peripheral fat and these results suggest that the larger hips of women may contribute to the sex difference in serum leptin concentration.

Relationship between blood pressure and body mass index in lean populations

Associations between body mass index (BMI) and blood pressure (BP) have been consistently observed, but remain poorly understood. One unresolved question is whether there is a linear relationship across the entire BMI range. We investigated this question among 11,235 adult men and women from seven low-BMI populations in Africa and the Caribbean. We used kernel smoothing and multivariate linear and spline regression modeling to examine gender differences in the relationship and to test for a threshold. Age-adjusted slopes of BP on BMI were uniformly higher in men than women, with pooled slope ratios of 2.00 and 2.20 for systolic and diastolic BPs, respectively. Men displayed no evidence of age modification or nonlinearity in the relationship, and the age-adjusted slope of systolic BP on BMI was 0.90 (95% confidence interval [CI], 0.76 to 1.04). Women demonstrated both age modification and nonlinearity. For both younger (<45 years) and older (45+ years) women, the optimal change point for a single threshold model was found to be 21 kg/m2. Slopes of systolic BP on BMI above this threshold were positive and significant: 0.68 (95% CI, 0.54 to 0.81) and 0.53 (95% CI, 0.29 to 0.76) for younger and older women, respectively. Slopes below the threshold were essentially zero for both groups of women, and the difference between the slopes above and below the threshold was significant for younger women (P=.019). In summary, we observed a threshold at 21 kg/m2 in the relationship between BMI and BP for women but not for men. This contributes to the effort to identify the mechanisms that underlie this relationship and how they differ by gender.

Socioeconomic status and health in blacks and whites: the problem of residual confounding and the resiliency of race

A large number of epidemiologic studies have focused on racial/ethnic differences, particularly between blacks and whites. Because health endpoints and racial categorizations are associated with socioeconomic status, investigators generally adjust for socioeconomic indicators. The intention is usually to control for confounding, thereby making groups comparable and excluding socioeconomic status as an alternative explanation to hypotheses of innate physiologic differences. A threat to the validity of these analyses is therefore the presence of residual confounding. We identify four potential sources of residual confounding in this analytical design: categorization of socioeconomic status variables, measurement error in socioeconomic indicators, use of aggregated socioeconomic status measures, and incommensurate socioeconomic indicators. Using simulations and examples from the literature, we demonstrate that the effect of residual confounding is to bias interpretation of data toward the conclusion of independent racial/ethnic group effects. Investigators often refer to possible "genetic" differences on the basis of models that control for socioeconomic status. We propose that such conclusions on the basis of this analytical strategy are generally unwarranted. Racial/ethnic differences in disease are a pressing public health concern, but the current approach does not often provide a basis for inference about putative biological factors in the etiology of this disparity.

Mortality from coronary heart disease and cardiovascular disease among adult U.S. Hispanics: findings from the National Health Interview Survey (1986 to 1994)

OBJECTIVES

We sought to estimate the coronary heart disease (CHD) and cardiovascular disease (CVD) mortality experience of U.S. Hispanics.

BACKGROUND

Limited information is available concerning the mortality from CHD among U.S. Hispanics, the nation's second largest minority group.

METHODS

The study used data from the National Health Interview Survey (1986 to 1994), including representative national samples of 246,239 non-Hispanic whites, 38,042 blacks and 14,965 Hispanics who were > or = 45 years old at baseline. Mean follow-up of mortality was 5 years (range 1 to 10).

RESULTS

During the follow-up period, 27,702 whites (11%), 4,976 blacks (13%) and 1,061 Hispanics (7%) died. Among men, the age-adjusted total mortality per 100,000 person-years was 3,089 in whites and 2,466 in Hispanics, and among women, it was 1,897 and 1,581 in whites and Hispanics, respectively. The Hispanic/white mortality rate ratio for CHD was 0.77 (95% confidence interval [CI] 0.64 to 0.93) and 0.82 (95% CI 0.66 to 1.01) for men and women, respectively. The rate ratio was 0.79 (95% CI 0.68 to 0.91) and 0.80 (95% CI 0.69 to 0.94), respectively, for mortality from cardiovascular diseases. Given the lower all-cause mortality in Hispanics, the proportion of total deaths due to CHD and CVD was similar between the two populations for the same gender and were, respectively, 29.7% and 44.7% in white men, 28.1% and 44.3% in Hispanic men, 24.9% and 43.2% in white women and 24.1% and 41% in Hispanic women.

CONCLUSIONS

These data from a cohort of a large national sample are consistent with vital statistics that show that all-cause, CHD and CVD mortality is approximately 20% lower among adult Hispanics than among whites in the United States.