Tracking physical growth and health status of South African rural children : Ellisras longitudinal study (ELS)

Abstract

Motivation -

In under-developed and developing countries malnutrition is a major cause of mortality. Despite the long-standing use of anthropometry for assessing growth and nutritional status of children in Africa based on cross-sectional studies, a number of issues remained unresolved. Today there is an increasing awareness that the spiraling cost of medical and health services must be stopped and that our society would be better served by devoting more effort to research in methods of primary prevention. Hence longitudinal studies are needed to combat the nutritional status of rural South African children, which is clearly seen as a growing social problem. Objectives - In this thesis chronic and acute malnutrition will be investigated both cross-sectionally and longitudinally in rural South African children aged 3 to 12 years who will participate in the Ellisras Longitudinal Study (ELS). Data was collected from November 1996 to November 1998. The aim of the study is fourfold: • to describe the growth and nutritional status of Ellisras rural children aged 3-10 years old • to determine the prevalence of stunting and wasting in a cross-sectional sample of Ellisras rural children aged 3 to 10 years in relation to their socio-economic background • to assess tracking of the nutritional conditions of Ellisras rural children aged 3 to 12 years by means of evaluating the stability of anthropometric indicators over a twoyear period (1996-1998) and • to investigate the stability of somatotype in Ellisras children aged 3 to 12 and relate this to their nutritional status.

Methodology - Anthropometric measurements which include height, weight, body circumferences ( calf, upper arm flexed), breadths (bi-epicondylar humerus and femur) and skin-folds (triceps, sub-scapular, supraspinale, calf) were carried out from November 1996 to November 1998 on children who participated in the Ellisras Longitudinal Study according to standard procedures recommended by Norton & Olds (1996). The total number of subjects in the study is clearly stated in each published paper of this thesis. To examine the prevalence of malnutrition in the sample, the National Health and Nutritional Examination Survey (NHANES III) or National Centre for Health Statistics (NCHS) reference data were used to determine both the weight-for-age and height-for-age and weight-for-height Z score. The breadwinner's occupation was used to describe the socio-economic status of each subject in relation to his or her nutritional status. The Heath-Carter method of somatotyping was used to somatotype these children. Results and Discussion of the individual studies: ► In analysing the results cross-sectionally, it is evident that the ELS children experience poor growth throughout the age group. Patterns of growth in height suggest that these children grow parallel to the 50th centile of the NHANES III up to age six and then both sexes demonstrate a gradual decline in height velocity such that their mean heights diverge by approximately 0.5 cm per year. In both sexes increase in weight is consistently between 1 and 2kg per year in contrast to the increments of the reference sample that gradually increase to approximately 3kg per year by 10 years of age. The prevalence of chronic and acute malnutrition was high for this sample at an older age. ► The prevalence of stunting in all three (high, moderate and low) socio-economic groups ranged from 19.9% to 51.0%, while for wasting it ranged from 22.8% to 39.9% in all socio-economic groups. There is an ongoing social dilution of higher and lower social classes in the Ellisras rural community, but with considerable selectivity in the process.

► Ellisras children generally experience poor nutritional conditions. Based on the tracking analyses, it is clear that poor nutritional status is relatively stable over a period of two years. It appears that the acute and chronic poor nutritional conditions of the ELS children in this report do not improve but instead worsen with increasing age. The strong positive tracking coefficients in this sample could enhance the prediction of future values for the subject who experiences acute and chronic poor nutritional conditions at the initial stage of the measurements. ► Ellisras rural boys are stable while others are extremely variable with changes of two to six times greater than the most stable boys are. Their mean somatotypes shift from balanced ectomorphy to mesomorphic ectomorph and vice versa over time. Migratory distances (MD) showed that the somatotype of some boys are stable while those of others vary with changes up to two or more times greater than the most stable boys. The inter-age partial correlations for endomorphs and ectomorphy are high and significant but low and insignificant in mesomorphy. ► Some girls in each group are stable while others are extremely variable with substantially greater changes than the most stable girls. The mean somatotype shifts from mesomorph-ectomorph to balanced ectomorph for the pre-school girls as well as from mesomorphic ectomorph and mesomorph-ectomorph to balanced ectomorph in the primary school girls. Examination of MD patterns over two years indicates that the somatotypes of individuals may show considerable change. MD values ranged from 2.6 to 24.4. This indicates that some pre-school girls vary up to 6.9 times and primary school girls 7.2 times more than others. Somatotype analysis confirms the poor nutritional status of these girls. Combined discussion - The prevalence of acute and chronic malnutrition is high in rural South African children, irrespective of their socio-economic status. This probably accounts for the fluctuations in the somatotype components found in the present study. Healthy, active and well-nourished children are a fundamental pre-requisite for sustained economic development.

Nevertheless, it seems important to take into account the fact that the high values for the indicators of wasting and stunting in this study are of major concern to the South African rural population. Therefore, interventions to improve the nutritional status of rural South African children should already be focussed on young children.