The Relationship between Body Mass Index and Blood Pressure in Adolescent School Children

INTRODUCTION: Adolescents form prospective human resource for the society. Besides physical growth and development, significant physiological changes also take place during adolescent period, both among boys and girls. The period of transition from childhood to adulthood is hazardous for adolescent health, because they often develop behavioural problems and improper life style changes in absence of proper guidance and counselling, which has its reflection in the form of various diseases in adult life. One such disorder is essential hypertension, in which the risk factors for development have its initiation during childhood and adolescence. Investigations of the correlates of blood pressure in children and adolescents carried out in developed countries suggest that blood pressure level in children and adolescents are associated with various personal, social and environmental factors such as gender, race, weight, height and social class(1). The relationship between body mass and blood pressure has been established more than 70 years ago(2). Both cross sectional and longitudinal studies(3,4) in western populations have consistently identified an association between overweight and hypertension. Several clinical trials have also shown an effect of weight reduction in lowering blood pressure(5,6). Body weight adjusted for height is often used as an alternative to the measurement of adipose tissue mass in the evaluation of individuals or population for obesity(7). One such measure in widespread use is Quetelet’s index, which is body weight (in kg) divided by height (in m2)(7). Better known as Body Mass Index (BMI), this measure is promulgated by the World Health Organization (WHO) as the most useful epidemiological measure of obesity. AIM OF STUDY: To assess the relationship between the Body Mass Index and the Blood Pressure in adolescent school children from three different localities (urban, semi urban and rural areas) in and around Madurai. DISCUSSION: The relationship between BMI and blood pressure is of crucial interest in evaluating both public health and the clinical impact of the so called obesity epidemic. In this study we have included 2494 children from three schools one each from urban, semi urban and rural area in and around Madurai. The purpose of our study is to find out the relationship between BMI and blood pressure in adolescent children. So, the study group was restricted to children in the age group of 13- 17 years. In this study, the height, the weight and the blood pressure of the children were measured along with systemic examination. From this the BMI was calculated in each child and they were classified based on age and sex specific BMI charts (WHO). The mean values of BMI, systolic and diastolic blood pressure were derived and analysed. The present study showed the incidence of “at risk for overweight” was 5.8% and overweight /obesity was 0.8%. A higher percentage of girls than boys were at or above the 85th percentiles of BMI. When compared with Western studies, the incidence of overweight and obesity were less in our study. This study showed that, the mean BMI was significantly higher in urban and semi urban school children in all age groups when compared with rural school children. At the same time children from semi urban school had lesser BMI values than urban school children. In all these three study groups, girls had more BMI values than boys in their respective age group. CONCLUSION: 1. The overall incidence of “at risk for overweight” and “overweight/obesity” was 5.8 and 0.8% respectively. 2. Girls are more in the category of “at risk for overweight” than boys whereas boys dominate in the overweight / obese group in their respective age. 3. The incidence of overweight and obesity is more in urban and semi urban school children. 4. About 1/3 of children from rural school were underweight. 5. 1.52% children in our study had hypertension. 6. Incidence of obesity among rural school children in our study in nil. 7. Age and BMI has strong influence on blood pressure. Sex doesn’t have statistically significant association. 8. BMI is significantly associated with SBP and DBP in both sexes, even within BMI groups. This suggest that obesity is a strong risk factor for developing hypertension in both sexes and this finding emphasize the importance of the prevention of obesity in children and adolescents.