RESUMO
OBJECTIVE: The mean values for anthropometric traits vary across population groups and this variation is clearly determined for the most part by the environment. The familiarity of anthropometric traits also varies in reports from different populations, although this variation has not been shown to follow a consistent pattern. To examine whether heritability is influenced by socio-cultural factors, we conducted a cross-cultural study of populations of the African diaspora. PARTICIPANTS: Data were collected on 1868 family members from Nigeria, 623 from Jamaica and 2132 from metropolitan Chicago, IL, USA. MEASUREMENTS: Height and weight were measured and body mass index (kg/m(2)) calculated. Fat-free mass, fat mass and percentage body fat were estimated using bioelectrical impedance analysis. Plasma leptin concentrations were also measured. The proportion of variance attributable to additive genetic and non-shared environmental components was estimated with the maximum likelihood variance decomposition method. RESULTS: Mean values for all anthropometric traits increased along the socio-cultural gradient, and obesity increased from 5% in Nigeria to 23% in Jamaica and 39% in the USA. Within populations the relationships among traits both within individuals and within families were highly consistent. Heritability estimates for weight, body mass index, fat mass and percentage body fat were approximately 50% for all groups. Heritability for height was lower in Nigeria (62%) than in Jamaica (74%) or the US (87%). CONCLUSION: The familial patterns of body size and energy storage appear to be consistent in these genetically related populations across a wide range of environmental conditions.
Assuntos
População Negra , Constituição Corporal/etnologia , Índice de Massa Corporal , Leptina/sangue , Adulto , Antropometria , Constituição Corporal/genética , Comparação Transcultural , Impedância Elétrica , Meio Ambiente , Feminino , Humanos , Jamaica/etnologia , Masculino , Nigéria/etnologia , Obesidade/etnologia , Obesidade/genética , Estados Unidos/etnologiaRESUMO
BACKGROUND: Waist circumferences (WC) >/=94 cm for men and >/=80 cm for women (action level I) and >/=102 cm for men and >/=88 cm for women (action level II) have been suggested as limits for health promotion purposes to alert the general public to the need for weight loss. In this analysis we examined the ability of the above cut-off points to correctly identify subjects with or without hypertension in Nigeria, Cameroon, Jamaica, St Lucia and Barbados. We also determined population- and gender-specific abdominal adiposity cut-off points for epidemiological identification of risk of hypertension. METHODS: Waist measurement was made at the narrowest part of the torso as seen from the front or at midpoint between the bottom of the rib cage and 2 cm above the top of the iliac crest. Sensitivity and specificity of the established WC cut-off points for hypertension were compared across sites. With receiver operating characteristics (ROC), population- and gender-specific cut-off points associated with risk of hypertension were determined over the entire range of WC values. RESULTS: Predictive abilities of the established WC cut-off points for hypertension were poor compared to the specific cut-off points estimated for each population. Different values of WC were associated with increased risk of hypertension in these populations. In men, WC cut-off points of 76, 81, 80, 83 and 87 cm provided the highest sensitivity for identifying hypertensives in Nigeria, Cameroon, Jamaica, St Lucia and Barbados, respectively. The analogous cut-off points in women were 72, 82, 85, 86 and 88 cm. CONCLUSIONS: The waist cut-off points from this study represent values for epidemiological identification of risk of hypertension. For the purpose of health promotion, the decision on what cut-off points to use must be made by considering other additional factors including overall impact on health due to intervention (e.g. weight reduction) and potential burden on health services if a low cut-off point is employed. There is a need to develop abdominal adiposity cut-off points associated with increased risks for cardiovascular diseases in different societies, especially for those populations where the distribution of obesity and associated risk factors tends to be very different from those of the technologically advanced nations. International Journal of Obesity (2000) 24, 180-186
Assuntos
População Negra , Composição Corporal , Doenças Cardiovasculares/genética , Promoção da Saúde , Hipertensão/genética , Obesidade/genética , Abdome , Adulto , África Ocidental/epidemiologia , Distribuição por Idade , Idoso , Antropometria , Área Sob a Curva , Doenças Cardiovasculares/etiologia , Doenças Cardiovasculares/prevenção & controle , Feminino , Humanos , Hipertensão/etiologia , Hipertensão/prevenção & controle , Masculino , Pessoa de Meia-Idade , Obesidade/complicações , Obesidade/epidemiologia , Obesidade/prevenção & controle , Valor Preditivo dos Testes , Curva ROC , Fatores de Risco , Sensibilidade e Especificidade , Distribuição por Sexo , Índias Ocidentais/epidemiologiaRESUMO
OBJECTIVES: The objective of this investigation was to examine the prevalence of abdominal adiposity and its association with the prevalence of hypertension among African descent populations in Nigeria, Cameroon, Jamaica, St. Lucia, Barbados, and the United States (US). RESEARCH METHOD: The data for this investigation were obtained from the International Collaborative Study on Hypertension in Blacks. Hypertension was defined as mean diastolic blood pressure > or =90 mmHg, systolic blood pressure > or = 140 mmHg or current treatment with prescribed anti-hypertension medication. Abdominal overweight was defined as waist circumference (WC) > or =94 and > or =80 cm for men and women, respectively. Abdominal obesity was defined as WC > or =102 and > or =88 cm for men and women, respectively. We estimated the site-specific prevalence of abdominal overweight and obesity across age and body mass index cut-points. We also calculated the population attributable fraction (AF) of hypertension due to abdominal adiposity. RESULTS: The prevalence of hypertension in these populations was tightly linked to abdominal adiposity. Increases in abdominal overweight accompanied an increasing degree of Westernization, rising from 6.4% and 26.3% in Nigeria, 16.5% and 62.8% in Cameroon, 15.8% and 58.6% in Jamaica, 14.3% and 62.1% in St. Lucia, 21.4% and 70.3% in Barbados to 38.9%, and 76.4% in the US for men and women, respectively. The corresponding values for abdominal obesity were 1.6% and 12.3% in Nigeria, 5.1% and 38.9% in Cameroon, 5.5% and 34.0% in Jamaica, 2.7% and 40.7% in St. Lucia, 7.8% and 44.7% in Barbados to 21.7% and 54.1% in the US for men and women, respectively. Body mass index-adjusted estimates of AF suggest that in most of these populations, especially in females, avoidance of abdominal overweight or obesity would help to curb the development of hypertension. DISCUSSION: An important public health challenge is to clarify how lifestyle factors influence risks of abdominal adiposity and ultimately the increased risk of cardiovascular diseases.
Assuntos
Abdome , Tecido Adiposo , Composição Corporal , Constituição Corporal , Hipertensão/epidemiologia , Adulto , África Ocidental/etnologia , Idoso , Barbados/epidemiologia , Índice de Massa Corporal , Camarões/epidemiologia , Feminino , Humanos , Hipertensão/etiologia , Jamaica/epidemiologia , Masculino , Pessoa de Meia-Idade , Nigéria/epidemiologia , Obesidade/complicações , Obesidade/epidemiologia , Santa Lúcia/epidemiologia , Estados Unidos/epidemiologiaRESUMO
The prevalence of type 2 diabetes, impaired glucose tolerance and associated risk factors were compared in sample surveys in Africa and the Caribbean with the Third National Health and Nutrition Survey (NHANES-III) from the United States. A total of 856 Nigerians, 1286 Jamaicans, and 1827 US blacks were included in the study. Body mass index (BMI) increased in a stepwise fashion across the three populations groups, ie, 23 kg/m2 in Nigerians, 26 kg/m2 in Jamaicans, and 28 kg/m2 in US blacks. The corresponding age-adjusted prevalences of type 2 diabetes among persons aged 25-74, were 1%, 12%, 13%. Jamaican women were found to have the same prevalence of type 2 diabetes as US women (14 vs 13%, respectively); mean BMI was likewise very similar (28 kg/m2 in Jamaican and 29 kg/m2 in US women). BMI and waist-to-hip ratio were both associated with type 2 diabetes prevalence. Findings of this study confirm the marked gradient in type 2 diabetes risk among these genetically related populations and suggest that the blacks in the island nations of the Caribbean and the United States are at particularly high risk. Nigerians exhibited remarkably well-preserved glucose tolerance. Understanding the factors that limit the risk of type 2 diabetes in West Africa, beyond relative absence of obesity, would have considerable public health significance.
Assuntos
Negro ou Afro-Americano/estatística & dados numéricos , Índice de Massa Corporal , Diabetes Mellitus Tipo 2/etnologia , Intolerância à Glucose/etnologia , Adulto , Idoso , Biometria , População Negra , Distribuição de Qui-Quadrado , Feminino , Humanos , Jamaica/epidemiologia , Masculino , Pessoa de Meia-Idade , Nigéria/epidemiologia , Razão de Chances , Prevalência , Análise de Regressão , Fatores de Risco , Estados Unidos/epidemiologiaAssuntos
População Negra , Hipertensão/epidemiologia , África , Dieta , Gorduras na Dieta/administração & dosagem , Humanos , Hipertensão/etiologia , Hipertensão/genética , Obesidade/complicações , Fatores de Risco , Fatores Socioeconômicos , Sódio na Dieta/administração & dosagem , Estresse Fisiológico , Estados Unidos , Índias OcidentaisRESUMO
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.
Assuntos
População Negra , Composição Corporal/fisiologia , Diabetes Mellitus Tipo 2/etnologia , Diabetes Mellitus Tipo 2/epidemiologia , Hipertensão/etnologia , Hipertensão/epidemiologia , Adulto , Negro ou Afro-Americano/estatística & dados numéricos , Idoso , Glicemia/análise , Doenças Cardiovasculares/complicações , Doenças Cardiovasculares/etnologia , Estudos Transversais , Feminino , Humanos , Jamaica/epidemiologia , Masculino , Pessoa de Meia-Idade , Nigéria/epidemiologia , Fatores de Risco , Fatores Sexuais , Estados Unidos/epidemiologiaRESUMO
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.
Assuntos
Estatura , Índice de Massa Corporal , Peso Corporal , África Ocidental/etnologia , Barbados , Estatura/genética , Peso Corporal/genética , Camarões , Feminino , Humanos , Jamaica , Modelos Lineares , Masculino , Nigéria , Obesidade/diagnóstico , Santa Lúcia , Reino Unido , Estados UnidosRESUMO
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.
Assuntos
População Negra , Composição Corporal , Proteínas/metabolismo , Tecido Adiposo , Adulto , Feminino , Humanos , Jamaica/etnologia , Leptina , Masculino , Pessoa de Meia-Idade , Nigéria/etnologia , Estados Unidos/etnologiaRESUMO
OBJECTIVE: Rates of non-insulin-dependent diabetes mellitus have risen sharply in recent years among blacks in the U.S. and the U.K. Increases in risk have likewise been observed in the island nations of the Caribbean and in urban West Africa. To date, however, no systematic comparison of the geographic variation of NIDDM among black populations has been undertaken. RESEARCH DESIGN AND METHODS: In the course of an international collaborative study on cardiovascular disease, we used a standardized protocol to determine the rates of NIDDM and associated risk factors in populations of the African diaspora. Representative samples were drawn from sites in Nigeria, St. Lucia, Barbados, Jamaica, the United States, and the United Kingdom. A total of 4,823 individuals aged 25-74 years were recruited, all sites combined. RESULTS: In sharp contrast to a prevalence of 2% in Nigeria, age-adjusted prevalences of self-reported NIDDM were 9% in the Caribbean and 11% in the U.S. and the U.K. Mean BMI ranged from 22 kg/m2 among men in West Africa to 31 kg/m2 in women in the U.S. Disease prevalence across sites was essentially collinear with obesity, pointing to site differences in the balance between energy intake and expenditure as the primary determinant of differential NIDDM risk among these populations. CONCLUSIONS: In ethnic groups sharing a common genetic ancestry, these comparative data demonstrate the determining influence of changes in living conditions on the population risk of NIDDM.
Assuntos
População Negra , Índice de Massa Corporal , Diabetes Mellitus Tipo 2/epidemiologia , Adulto , África Ocidental/etnologia , Fatores Etários , Idoso , Constituição Corporal , Diabetes Mellitus Tipo 2/etnologia , Diabetes Mellitus Tipo 2/genética , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Nigéria/epidemiologia , Prevalência , Fatores de Risco , Distribuição por Sexo , Reino Unido/epidemiologia , Estados Unidos/epidemiologia , Índias Ocidentais/epidemiologiaRESUMO
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.