Our study of Epidemic Hypertension in Nigerian Workers has successfully recruited 501 male and 303 female civil servants, ages 20-64, in Benin City, a population of genetic relevance to U.S. blacks. This population appears to be in transition from a low prevalence of hypertension to a high prevalence of hypertension. Among the higher socioeconomic status (SES) males (Senior staff), we found a twofold higher prevalence of hypertension than in the lower SES males (Junior staff). Smaller differences were observed by staff status in females. Mean body mass index (BMI) was very low in the males (22.9 in Senior and 21.4 in Junior staff) and low in females (25.0 in Senior and 23.8 in Junior staff). Hypertension was associated with higher body mass index, waist girth, fasting insulin, and lower physical activity. Differences in hypertension rates between SES groups could not be attributed to differences in sodium or potassium excretion, macronutrient intake, alcohol intake, cardiovascular reactivity, or measured stressors. There was a high prevalence of left ventricular hypertrophy, based on ECG voltage criteria (ECG-LVH), in both Senior and Junior staff, males and females, which was related to hypertension, but was not uncommon in normotensives. Among males, there appeared to be a threshold effect for BMI on blood pressure around the median BMI, 21.5. Further analyses suggested that, above the BMI threshold, adult weight gain is a stronger determinant of blood pressure than pre-adult weight. Adult weight gain appeared to be predominantly central weight gain. However, only longitudinal data can support such a conclusion. We hypothesize that blood pressure in blacks is very sensitive to central weight gain and related changes in insulin. It seems likely that optimal weight for blacks is far lower than that considered normal in the U.S. We propose a longitudinal study of this cohort to determine the importance of weight gain and weight-related factors, and the possible interaction of other factors, e.g. psychosocial, electrolytes, reactivity, macronutrient intake, to change in blood pressure. Factors related to weight gain will be identified. The high prevalence of ECG-LVH will be validated against echocardiographic measures (ECHO-LVH), and we will identify the predictors of change in ECG-LVH, and the correlates of microalbuminuria. In Year 2 (Cohort Year 4) we will restudy half of the population with echocardiography, cardiovascular reactivity, and new psychosocial measures. In Year 4 (Cohort Year 6), with the exception of cardiovascular reactivity, we will repeat baseline measures in the full cohort, including multiple blood pressure measures, height, weight, waist, hips, ECG, physical activity, two 24 hour dietary recalls, alcohol intake, menopausal status, psychosocial measures, 24 hour urine for Na, K, creatinine, micro-albuminuria, and fasting serum for lipids, insulin, glucose, and creatinine. This dynamic population provides a valuable opportunity to gain important information about the etiology of hypertension which would be much more difficult to gain from a U.S. black population because higher weight and blood pressure are already entrenched and static in the U.S. population.
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