Relationship of “weight for height” to “height for age” — a longitudinal study

NUTRITION RESEARCH, Vol. 6, pp. 369-373, 1986 0271-5317/86 $3.00 + .00 Printed in the USA. Copyright (C) 1986 Pergamon Press Ltd. All r i g h t s reserved.

RELATIONSHIP OF "WEIGHT FOR HEIGHT" TO "HEIGHT FOR AGE" - A LONGITUDINAL STUDY Frank-P. Schelp, Praneet Pongpaew, Niyomsri Vudhivai and Santasiri Sornmani Department of Epidemiology, I n s t i t u t e of Social Medicine Free University Berlin; German Agency f o r Technical Cooperation (GTZ) Federal Republ~c of Germany and Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand ABSTRACT The development of four age cohorts of preschool children from 0 to 5, 6 to I I , 12 to 23 and 24 to 60 months according to weight f o r height and height f o r age, as well as weight for age, was followed f o r 1 year. All n u t r i t i o n a l parameters declined in the two cohorts 0 to 5 and 6 to II month-old children. Weight for height recovered subsequently to almost the same level as that of the North American children in the age groups 12 to 60 months, whereas the age dependent parameters remained well below the North American standard. The individual variations of weight f o r height and height for age were followed up in 6 case studies for 20 months. I t appears that the organism gives main p r i o r i t y to an optimal r e l a t i o n s h i p of weight to height e i t h e r , by reducing the growth spurt as was observed over the observation period, or, by l i m i t i n g growth altogether. The phenomenom of "stunting" is interpreted as an adaptation process which is not necessarily due to undernourishment in the past. I f the n u t r i t i o n a l status is assessed by the parameter weight f o r age, investigators must recognize f u l l y i t s l i m i t a t i o n s . KEY WORDS: Weight for height, height for age. INTRODUCTION Weight for height is regarded as an index of the current n u t r i t i o n a l status, and height f o r age is said to r e f l e c t the n u t r i t i o n a l conditions in the past ( I ) . Besides inadequate food intake, with or without i n f e c t i o n , a certain deficiency of protein intake and undernutrition at a period when growth is p a r t i c u l a r l y sensitive, had been discussed as underlying causes for stunting (2). SUBJECTS AND METHODS Two v i l l a g e s , Ban Kok and Ban Pak Puey, in the Nam Pong i r r i g a t i o n area of Khon Kaen province, Northeast Thailand, located approximately 500 km north-

Correspondence: Department of Epidemiology, I n s t i t u t e of Social Medicine, Free University Berlin, Kelchstr. 31, D-lO00 Berlin 41, Federal Republic of Germany. 369

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northeast of Bangkok, had been selected for t h i s survey. The v i l l a g e r s of Ban Pak Puey are solely farmers; some of the v i l l a g e r s of Ban Kok work, however, in the provincial centre. Nevertheless, the main occupation is s t i l l farming. The Nam Pong i r r i g a t i o n area has already been described in detail previously (3). Approximately 185 children from b i r t h up to 60 months of age had been under observation. These were all the children in t h i s p a r t i c u l a r age range residing in the v i l l a g e s . Measurement followed standard precedures and p a r t i c u l a r emphasis was laid on the accuracy of measuring length under 29 months of age. The data were evaluated only once every t h i r d month. B o d y weight was measured by using a beam balance (Detecto model 239). The balance was calibrated on each day of measurement b y using a standard weight. The children were dressed only in l i g h t clothing. The length of the children under 29 months of age was measured by using a measuring tape f i x e d to a true v e r t i c a l f l a t surface and the c h i l d was held by two persons. The height of older children was measured by using a measuring scale attached to the balance. The results of the measurements were expressed, using the reference data from the US Center for Health S t a t i s t i c s and SD scores had been calculated according to Waterlow et al. ( 4 ) . RESULTS The children were grouped into 4 age cohorts i . e . 0 to 5 months, 6 to II months, 12 to 23 months and 24 to 60 months according to t h e i r ages in June 1982. From June 1982 up to June 1983, for 5 measuring points, the median of individual SD scores: weight f o r height, height for age and weight f o r age were claculated. The variations in the number of children in each cohort are due to migration and u n a v a i l a b i l i t y when taking measurements at certain measuring points. The reduction of the number of children in the oldest age cohort was due to a drop-out of those children whose ages exceeded 60 months (Fig. I ) . There is a d i s t i n c t reduction in weight f o r height in the age range 0 to II months. Weight according to height improved again after the f i r s t year of l i f e , and in the oldest age range, the reduction in weight for height is only approximately 0.5 SD scores below the North American standard. Height for age SD scores also decreased in the age range 0 to 5 and 6 to II months and remained around or below -2.00 SD from the American standard from I year of age onwards. Weight for age SD scores follow almost the same pattern as height for age. In Fig. 2, from June 1982 to March 1984, the development of weight for height and height f o r age is followed for three generally healthy children. In the case of the child no. 0453, both parameters are close to the medians of the reference population f o r weight for height and height f o r age from the 7th to the 16th month. Subsequently, there is an indication of s l i g h t overweight in December ]983, whereas the height of the child is below -1SD when compared with those of i t s Western counterparts. The n u t r i t i o n a l status of the c h i l d no. 0028 improved steadily from the 6th to the 27th month according to her weight for height but her height remained very low i . e . between -2.50 and -3.50 SD of the standard. A d i f f e r e n t s i t u a t i o n can be observed in the development of the child no. 0777. Throughout the whole observation period she ramained well nourished and gradually adjusted her height towards the median of the standard as well, a f t e r being d e f i n i t e l y below -1.50 SD height f o r age at the beginning of the observation period.

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The child no. 03858 was d e f i n i t e l y underweight at the time he was included into the project. However, within three months he recovered e n t i r e l y and remained well-nourished ever since. His recovery was accomplished by a reduction in his growth spurt. He scored the lowest for height for age 7 months a f t e r his recovery from acute undernutrition and caught up with his growth a f t e r that. DISCUSSION The two v i l l a g e s under investigation were taken as part of a n u t r i t i o n a l intervention study from March 1981 to June 1985. Besides anthropometric measurements morbidity data were also compiled, but no biochemical information had been collected because the cooperation of the v i l l a g e r s deteriorates rapidly when blood has to be taken. I t is assumed that the pattern of weight and growth development observed in t h i s survey might be quite common amongst preschool children in the rural areas of Asian countries. The reduction in weight for height within the f i r s t year of l i f e to almost 1.5 SD scores from the standard weight might be due to the fact that all children are breast fed without adequate supplementary feeding; coinciding with observations made in other countries (5). A steady improvement in the older age groups in the relationship of weight to a given height can be observed (Fig. I ) . Dietary surveys undertaken in the Northeast of Thailand for three to six year-old children revealed an energy intake of around 700 to 1500 Kcal (2929 to 6276 KJ) per day and 15 to 30 g protein per day (6,7). This seems to be marginally below the energy and protein requirements as recommended by FAO/WHO 1973. Obviously, the children adapt to t h e i r n u t r i t i o n a l environment by l i m i t i n g t h e i r growth spurt in favour of an optimal weight in r e l a t i o n to a given height which almost equals those of children from a western i n d u s t r i a l i z e d country. In the l i g h t of these r e s u l t s , i t seems questionable whether "stunting" is a valuable indicator of the n u t r i t i o n a l status of preschool children. The results also indicate that i f weight for age is used as a n u t r i t i o n a l i n d i c a t o r , i t s serious l i m i t a t i o n s has to be taken into consideration. ACKNOWLEDGEMENTS This study was supported by the German Agency for Technical Cooperation Ltd. (GTZ), Project No. 74.2513.5. The authors wish to express t h e i r sincere thanks to Mr. Pongson Sitaputra from the Department of Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok f o r his help in conducting the f i e l d studies and Dr. Dankmar B~hning, Department of Epidemiology, I n s t i t u t e of Social Medicine, Free University Berlin for his assistance in data processing. REFERENCES I. Waterlow JC, Alleyne GAC. Protein malnutrition in children : advances in knowledge in the last ten years. Adv. Prot. Chem. 1971; 25:117-241. 2. Waterlow JC. Observation on the assessment of protein-energy malnutrition with special reference to stunting. Courrier 1978; 28:455-460.

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373

3. Schelp FP, Sornmani S, Egormaiphol S, Pongpaew P, Keller W, Harinasuta S, Migasena P. Physical growth of preschool children in relation to a water resource development scheme in Thailand. J. Trop. Pediatr. 1982; 28:187-192. 4. Waterlow JC, Buzina R, Keller W, Lane JM, Nichaman MZ, Tanner JM. The presentation and use of height and weight data for comparing the n u t r i t i o n a l status of groups of children under the age of I0 years. Bull. Wld. Hlth. Org. 1977; 55:489-498. 5. Waterlow JC, Ashworth A, G r i f f i t h s M. Faltering in less-developed countries. Lancet 1980; 2:1176-1178.

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6. Chandrapanond A, Ratchatasilipin A, Tansuphasiri S. Dietary survey of preschool children and expectant women in Soongnern D i s t r i c t . Nakorn Rajsima Province, Thailand. Am. J. Clin. Nutr. 1972; 25:730-735. 7. Migasena P, Thurnham DI, Pongpaew P, Hongthong K, Harinasuta C. Anthropometric studies in preschool children in Northeast Thailand. J. Nutr. Sci. Vitaminol. 1974; 20:127-132. Accepted for publication February 23, 1986.