Racial/ethnic differences in prehypertension in American adults: population and relative attributable risks of abdominal obesity.

To estimate the risk and population attributable risk of prehypertension that is due to abdominal obesity in White, Black and Hispanic American adults. To determine how much of the relative difference in the risk of prehypertension between high-risk Blacks and Hispanics and the low-risk group Whites that is attributable to their differences in abdominal obesity. Data (n=4016) from the 1999 to 2000 US National Health and Nutrition Examination Surveys were used in this study. Abdominal obesity was defined as waist circumference >/=102 and >/=88 cm in men and women, respectively. Prehypertension was defined as not being on antihypertensive medication and having systolic blood pressure of 120-139 mmHg or diastolic blood pressure of 80-89 mmHg. Odds ratio from the logistic regression analysis was used to estimate the risk of prehypertension that was due to abdominal obesity. To estimate prehypertension risk differences between low-risk Whites and high-risk Blacks and Hispanics that was due to abdominal obesity, we estimated relative attributable risk. Statistical adjustments were made for age, blood glucose, total cholesterol, current smoking and exercise. Abdominal obesity was associated with increased odds of prehypertension in Whites, Blacks and Hispanics. In men, abdominal obesity was associated with 44, 90 and 98% increased odds of prehypertension in Whites, Blacks and Hispanics, respectively. The corresponding values in women were 112, 198 and 104%. Proportions of risk of prehypertension explained by abdominal obesity were 15.2, 22 and 25.8% in White men, Black men and Hispanic men, respectively. The corresponding values in women were 38.8, 58.6 and 32.5%. Approximately, 7% of the differences in the risk of developing prehypertension between White and Black men and between White and Hispanic men may be attributable to differences in rates of abdominal obesity. The analogous values for women were approximately 39.7 and approximately 16.5%, respectively. In conclusion, despite having lower rates of abdominal obesity than their counterparts, Black men, Hispanic men and Hispanic women had high population attributable risks, indicating that factors other than abdominal obesity may have important explanatory power for racial differences in prehypertension in these groups. However, in Black women reduction in risk of prehypertension could be possible by instituting public health measures to reduce abdominal obesity to the levels seen in White women. Intervention programmes designed to reduce overall obesity may also lead to reduction of abdominal obesity, and consequently may curb prehypertension in these population groups. Life-style modification, including diet and exercise, may have public health significance in reducing the incidence of prehypertension in these populations.