[The study on relationship of body mass index and blood pressure in children and adolescents of Beijing].
OBJECTIVE: To identify the relationship of body mass index (BMI) and blood pressure in 7 - 15 years children and adolescents of Beijing so as to provide scientific basis for early prevention of hypertension and to provide evidence for verification on the category criterion of overweight and obesity in children and adolescents of China, recommended by the Working Group on Obesity in China (WGOC) to sensitively distinguish the blood pressure in normal weight, overweight and obesity populations. METHODS: A cross-sectional survey on epidemiological characteristics of obesity with stratified cluster sampling method carried out in Beijing in April and May, 2000. 5155 students aged 6 - 15 years were selecte das research subjects. The category criterion of overweight and obesity in children and adolescents of China was recommended by WGOC, the diagnostic criterion of hypertension in children was recommended by CDC in the USA. Statistics analysis system (SAS 8.1) including partial person correlation analysis, t-test, chi(2) test and logistic multi-factors regression analysis was used to analyses the data from 4982 subjects aged 7 - 15 years. RESULTS: (1) after the age and gender were adjusted, the BMI positive correlation with systolic blood pressure (SBP) and diastolic blood pressure (DBP) was found independent in 7 - 15 years children and adolescents (P < 0.0001) and the partial relation coefficients(r) between BMI and SBP and DBP were 0.323 87 and 0.245 88 respectively. (2) the means of SBP and DBP in obesity group were significantly higher then overweight, while overweight was significantly higher then normal weight group (P < 0.0001). (3) the prevalence rates of hyper-SBP, hyper-DBP and hypertension were significantly different (P < 0.0001). When compared with the normal weight group, the relation risk (RR) for hypertension in overweight group and obesity group were 2.96 and 4.85 respectively. The prevalence rates of hypertension in overweight and obesity group were 19.70% and 24.22% respectively. (4) the results of logistic multi-factors regression analysis showed that both age and weight were effecting on hyper-SBP, hyper-DBP and hypertension (P < 0.0001). After age was adjusted, the RR for hypertension was 2.62, and their confidence interval (CI) was 2.36 - 2.91 in obesity or overweight, between overweight and normal weight. CONCLUSION: (1) the BMI positive correlation with SBP and DBP was found independent in 7 - 15 years children and adolescents of Beijing, and the risk for hypertension maybe increased when these people with overweight and obesity, it is very important for hypertension prevention and control that overweight and obesity prevention and control in children and adolescents. (2) the sensitivity of the category criterion of overweight and obesity in children and adolescents of China, recommended by WGOC have been verified on distinguish the blood pressure in normal weight, overweight and obesity populations.