Body mass index and waist circumference as markers of arterial hypertension in adolescents

Objective: To evaluate the sensitivity and specificity of anthropometric measurements of body fat in a sample of Brazilian adolescents for the prediction of hypertension. Methods: The arterial blood pressure was measured on two visits in a sample of 456 students aged 12 to 17 years, from public and private schools of the Fonseca neighborhood, in Niterdi between 2003 and 2004. A subject was defined as hypertensive if he/she had systolic and diastolic pressures above the 95(th) percentile for sex, age and height. A questionnaire was applied and Body Mass Index (BMI) and waist circumference (WO measurements were made. Results: A statistically significant correlation was observed between hypertension and the cutoff points considered unfavorable, both for BMI and WC. The greatest association was with the cutoff point proposed for the Brazilian population. As to the BMI sensitivity used for American Black or White populations or for the Brazilian population, we found 52.4% to 57.1% and 52.4%, respectively. And BMI specificity was 69.3%, 70.0% and 80.88%, respectively. The sensitivity found in our sample, relative to the cutoff points for WC proposed for all American ethnic groups, was also low (45.0%) and specificity was a little higher (77.6% and 74.5%, respectively). Conclusion: Existing American WC measurements showed low sensitivity and specificity for hypertension in our population. As to BMI, the available cutoff points also showed a low level of sensitivity. There is a need to establish body fat cutoff points that can provide a better prediction of cardiovascular risk.