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Biomedical subjects

R S Cooper

Publications and source records attributed to R S Cooper.

At least 73 records · Page 4Linked to original sources
PubMed1999

Blood pressure change in Africa: case study from Nigeria.

Studies of migrants and comparisons of rural versus urban communities are potentially informative study designs because they allow examination of genetically similar population subgroups exposed to diverse environmental conditions. These designs have been underused in Africa, where recent urbanization has created many situations in which nearby communities of common ethnicity and culture live under different social and economic circumstances. The International Study of Hypertension in Blacks (ICSHIB) conducted several overlapping surveys in Nigeria starting in 1993. These surveys were based primarily in the rural village of Idere and the urban community of Idikan, both inhabited by people defined ethnically as Oyo Yoruba and sharing a common language and culture. Survey teams collected standardized blood pressure and anthropometric measurements, and some study participants provided 24-hr urine samples and questionnaire data on psychosocial stress and social integration. Rural and urban groups differed substantially in blood pressure and related characteristics. Age-adjusted prevalence of hypertension (blood pressure > or = 140/90 mm Hg) for participants aged 25 years and older was 7-8% in Idere and 24-27% in Idikan. The distributions of overweight, sodium/potassium ratio, perceived stress, and social integration scores all contributed to lower hypertension risk in Idere. The effects and interactions of these identified risk factors remain poorly understood, even among people who share a common genetic background, similar diet, and many other lifestyle features. Nonetheless, the rural-urban distinction is sufficiently salient to engender a nearly threefold difference in hypertension prevalence. This disparity in disease prevalence demonstrates the sensitivity of human beings to the environmental determinants of disease and provides a sobering example of the difficulty in identifying subtle genetic effects, which can be easily overwhelmed by small differences in environmental exposures.

Adult↗
PubMed1999

Mortality among US adult Asians and Pacific Islanders: findings from the National Health Interview Surveys and the National Longitudinal Mortality Study.

OBJECTIVES: To assess the mortality of the adult Asian and Pacific Islander population in the United States. METHODS: Cohort study using data from the National Health Interview Survey (1986 to 1994) and the National Longitudinal Mortality Study. Deaths were ascertained by matching the National Death Index with average follow-ups of 5.3 and 9 years, respectively, for the two studies. RESULTS: Respondents from the pooled National Health Interview Surveys included 532,794 non-Hispanic whites, 94,242 blacks, 52,725 Hispanics, and 16,936 Asians and Pacific Islanders, all of whom were at least 18 years of age at baseline. The National Longitudinal Mortality Study included 373,397 non-Hispanic whites, 41,262 blacks, 23,356 Hispanics, and 8,390 Asians and Pacific Islanders. Overall age-standardized mortality was the lowest in Asians/Pacific Islanders, whose risk of death was about 40% lower than whites'. Adjustment for differences in education levels had a minimal influence on the mortality advantage in Asians/Pacific Islanders. CONCLUSIONS: Longitudinal cohorts provide an important source of health status information on Asians and Pacific Islanders. These two studies from representative national samples suggest that overall mortality is substantially lower among Asians and Pacific Islanders than in all other major ethnic groups.

Adolescent↗
PubMed1999

Limitations in the use of race in the study of disease causation.

Tremendous variation exists in the rates of many chronic diseases across racial groups. However, serious technical and conceptual limitations hamper the ability of racial comparisons to illuminate the causative pathways. First, race is confounded by social class, which is complex, and like other confounders of race, may not be measured with equal validity across racial groups. Second, statistical "adjustments" for race effects can be misleading since residual confounding may be misconstrued as a genetic effect. Third, the biologic concept of race tempts us to ignore the context dependency of genetic expression. When trying to detect genetic effects, both the environmental and genetic contributions must be measured and potential gene-environment interactions accounted for. Unfortunately, this process is beyond our current technical capabilities. To move forward on the problem of prostate cancer and other diseases distinguished by marked ethnic differentials, investigators need a more comprehensive understanding of the factors that mediate the apparent effect of race combined with valid measures of those factors, as well as novel strategies that can help overcome the technical and interpretive limitations of statistical adjustment. Finally, the "grand" theories of race-based genetic susceptibility must be replaced with rigorous criteria to determine when a trait can be ascribed to some genetic origin.

Causality↗
PubMed1998

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.

Adult↗
PubMed1998

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.

Black People↗
PubMed1998

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.

Adult↗
PubMed1998

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.

Africa, Western↗
PubMed1998

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.

Adolescent↗
PubMed1998

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.

Adipose Tissue↗
PubMed1998

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.

Africa↗
PubMed1998

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.

Adult↗
PubMed1998

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.

Adult↗
PubMed1998

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.

Adolescent↗