Relation between body mass index and body fat in black population samples from Nigeria, Jamaica, and the United States

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 Africa 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.(AU)

The prevalence of hypertension in seven populations of West African origin

OBJECTIVE: 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 percent in West Africa to 26 percent in the Caribbean and 33 percent 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.(AU)

Obesity and hypertension prevalence in populations of African origin

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, aged 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 cutpoints designating "overweight" and "obesity". The prevalence of these conditions ranged from 6 percent to 63 percent for overweight, from 1 percent to 36 percent for obesity, and from 12 percent to 35 percent for hypertension. Adjusted relative risks were similar in most sites, ranging form 1.3 to 2.3 for both cutpoints. We found that 6-29 percent of hypertension in each population was attributable to overweight and 0-16 percent to obesity. Comparing rural Africa with the United States, 43 percent of the difference in hypertension prevalence for women was attributable to overweight, and 22 percent for men, whereas respective values for obesity were 14 percent and 11 percent. 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.(AU)

Standardization of blood pressure measurement in an international comparative study

In the context of a collaborative study of hypertension in populations of West Africa origin procedures of standardization on the measurement of blood pressure were evaluated. Comparisons of means levels of blood pressure, which in large part determine prevalence rates, are highly sensitive to differences in technique. While rotating a single field team may be the ideal approach to multisite studies, it is not practical in international collaborative research. Appropriate techniques to standardize multiple teams over a long period of time have not been developed, however. In the present study 8981 individuals were examined in eight sites in six countries with the standard mercury sphygmomanometer. An evaluation of the effectiveness of central training, site visits, monitoring of digit preference, and the use of an electronic device for internal standardization is described. In all but one of the sites reliability was high and comparable to the observers at the Coordinating Center. Digit preference for the entire set of measurements was limited (frequency of terminal zero = 23.5 percent for systolic and 28.9 percent for diastolic readings) and could be shown to have virtually no effect on prevalence rates on correlation estimates. Mean differences among observers within a given site and between sites were small (ñ-5 mmHg). While logistically complex, these methods can provide the basis for standardization in international comparative blood pressure surveys.(AU)

Obesity in peoples of the African diaspora

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.(AU)

Obesity in the Caribbean

People of African origin who lived in the Caribbean share a common genetic heritage but live in socioeconomic environments that diverge widely. A cross-cultural study of males and females from Jamaica, St. Lucia and Barbados investigated the prevalence of hypertension and its environmental determinants. Standardized measurement techniques allowed comparable measurements of weight, height, waist and hip circumferences, and blood pressure. The population values for body mass index (BMI), per cent overweight (males BMI > or = 27.8 kg/m2; females BMI > or 27.3 kg/m2) and per cent obese (males BMI > or = 31.1 kg/m2; females BMI > or = 32.3 kg/m2) are presented. Prevalence of hypertension is based on the age-adjusted total population. The gradient in per capita gross national product in Jamaica, St. Lucia and Barbados parallels the gradient in the proportions of population in those countries who are obese. BMI explained 26 percent of the variance in blood pressure in females and 13 percent in males. Obesity is a significant problem in the Caribbean, as it is in many other developing countries, and it is associated with a high prevalence of hypertension, particularly in women.(AU)

Obesity in the Caribbean

People of African origin who live in the Caribbean share a common genetic heritage but live in socioeconomic environments that diverge widely. A cross-cultural study of males and females from Jamaica, St. Lucia and Barbados investigated the prevalence of hypertension and its environmental determinants. Standardized measurement techniques allowed comparable measurement of weight, height, waist and hip circumferences, and blood pressure. The population values for body mass index (BMI), percent overweight (males BMI > 27.8 kg/m; females BMI > 27.3 kg/m) and percent obese (males BMI > 31.1 kg/m; females BMI > 32.3 kg/m) are presented. Prevalence of hypertension is base on the age-adjusted total population. The gradient in per capita gross national product in Jamaica, St. Lucia and Barbados parallels the gradient in the proportions of populations in those countries who are obese. BMI explained 26 percent of the variance in blood pressure in females and 13 percent in males. Obesity is a significant problem in the Caribbean, as it is in many other developing countries, and it is associated with a high prevalence of hypertension, particularly in women.(AU)

Obesity in peoples of the African diaspora

People of African descent in the Caribbean and the USA originated from the Bight of Benin in West Africa. Although these population 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 of adults in Nigeria, Cameroon, Jamaica, St. Lucia, Barbados and the USA. In urban populations there was a trend toward 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.(AU)