Blood pressure: effect of body mass index and of waist circumference on adolescents.

BACKGROUND: Increased body mass index (BMI) and waist circumference (WC) have been associated with blood pressure elevation.

OBJECTIVE: To evaluate the effect of BMI and WC on blood pressure (BP) of adolescents.

METHODS: Cross-sectional analytical study including 536 adolescents from public and private schools. BMI was calculated and classified as high-normal (> or =50th p and < 85th p), overweight (> or =85th p and < 95th p), and obesity (> 95th p). WC was measured and considered increased if > 75th p. BP was considered elevated if > 90th p.

RESULTS: 319 (59.5%) adolescents were girls, the mean age was 14.0+/- 1.99 years, high-normal weight was found in 39.6%, overweight in 37.1% and obesity in 23.3%. The percentage of high SBP and DBP followed the increase in BMI (p=0.000), reaching 46.4% among boys and 39.3% among obese girls for SBP and 42.0% and 44.6% for DBP, respectively. High SBP and DBP were 3.9 and 3.4 times more frequent among boys and 2.2 to 2.0 times more frequent among girls with WC > 75th p, respectively. Using simple linear regression analysis, each increment in BMI would increase SBP by 1.198 mmHg, and in WC by 0.622 mmHg. The PR for elevated SBP and DBP in relation to BMI > or =85th p was 3.9 (95% CI 2.0-7.4[p=0.000]) and 4.3(95% CI 2.2-8.5[p=0.000]), respectively; in relation to WC > 75th p was 1.8(95% CI 1.0 to 3.0 [p=0.036]) and 1.4 (95% CI 0.8 to 2.4). BP > 90th p with WC < or =75th p was found in 16/181 (8.8%) of the adolescents with high-normal weight.

CONCLUSION: BMI and WC values have a strong influence on BP values in adolescents.