The prevelance of hypertension, obesity and the association of fat patterning with blood pressure in rural south african children aged 6 to 13 years: ellisras longitudinal growth and health study

Introduction

Hypertension and obesity is with no doubt, one of the major causes of death in developed and underdeveloped nations [1]. It is also suspected that essential hypertension and obesity may have its inception in childhood [2]. However, there is no published data on obesity, fat patterning and blood pressure in rural South African children to support these findings. The main objectives of this study were to determine the prevalence of obesity and hypertension in 6-13 year old Ellisras rural children in South Africa. Additionally the association of fat patterning and blood pressure were investigated.

Method

A total of 1884 subjects (967 boys and 917 girls), aged 6 to 13 years, who were part of the Ellisras Longitudinal Study [3] were studied. The anthropometric variables of height, weight, and triceps, biceps, subscapular, supraspinal skinfolds were measured according to the standard protocols described in Norton & Olds [4]. The proportion body fat on the trunk relative to that on the limbs was used as an indicator of the central pattern of body fat (visceral fat). Internationally recommended cut-off points for BMI in children were used in this study. Hypertension was define as average systolic or diastolic blood pressure greater than or equal to the 95th percentile for age and sex measured at least three separate occasion [5]. The association between the changes in the fat patterning ratios and blood pressure was investigated.

Results

Boys had a significantly greater mean ratio of subscapular to triceps, the sum of the trunk skinfold relative to the limb skinfold and trunk than girls in all the age groups while girls had a significantly greater mean sum of skinfolds in all the age groups. These indicates higher levels of visceral and lower fat patterning among boys as compare to girls in this sample. The prevalence of hypertension ranged between 4.4% to 9.1% for boys and 3.8% to 6.0% for girls from the age of 6 to 13 years. The prevalence of overweight in the present sample was relatively low (0 to 0.3% for boys and 0 to 0.7% for girls), however the prediction of these children to have a BMI  30 at adulthood was not prevalent in this sample.

Discussion and Conclusion

There are relative low hypertensive children in the rural South African population coupled with low prevalence of overweight. There was a weak association between fat patterning ratios with systolic and diastolic blood pressure. The need to manage hypertensive individual is evident in this sample so as to combat this chronic disease at an early age. Follow up studies should investigate the relationship between blood pressure and dietary electrolytes (sodium, potassium, calcium), dietary protein, lipids and fibers, alcohol and total energy consumption of these children.
Acknowledgement: The financial support received from Vrije University, Amsterdam, Netherlands and the University of the North, South Africa, National Research Foundation and Medical Research Council of South Africa for the Ellisras Longitudinal growth and Health study is thankfully acknowledged.

References

[1]. Seedat YK, et al. (1981). The prevalence of hypertension in rural Zulus. SA Med J, 51: 7-10.
[2]. Van Lenthe FJ, et al. (1994). Tracking blood pressure in children and youth. Am J Hum Biol, 6:389-399.
[3]. Norton K & Olds T. (1996). Anthropometrica. Sydney: University of New South Wales Press: 120- 267.
[4]. Monyeki KD et al. (2000). Growth and Nutritional status of rural South African children 3-10 years old: The Ellisras Growth Study. Am J Hum Biol, 12:42-49
[5]. Pediatrics (1996). National High Blood preasure Education program working group on hypertension control in children and adolescence ,pediatrics, 98 (4): 649-658