The association between high blood pressure, physical fitness, and body mass index in adolescents

Background The aim of this study was to analyze the association of fitness and fatness with blood pressure (BP) and hypertension. Methods This was a cross-sectional study of 13,557 boys and girls 15–20 years of age. Fitness was estimated from a shuttle run test, fatness from body mass index (BMI), and BP was measured sitting after 5 min of rest. Other lifestyle variables were self-reported. Results Boys had a higher systolic BP (SBP) than girls. A low physical fitness level and high BMI were independently associated with a high BP and risk of having hypertension in both girls and boys. Interaction was found between BMI and fitness. In a stratified analysis an odds ratio (OR) of 3.99 was found for hypertension in girls with a BMI > 25 kg m−2 compared to lean girls if all had a low fitness level, and an OR of 2.14 for a high BMI in girls with a high fitness level. In boys, OR for high versus low BMI were 3.23 in the low fit and 2.34 and 2.50 in the middle and upper tertile of fitness, respectively. Conclusions Fitness and BMI were independently associated to BP. BMI was a stronger predictor of hypertension in those with a low fitness level, especially in girls.