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Anthropometry of the Child
Anthropometric Status of the Mother
Nutritional Indices as Measures of Social Development
8.1. In the running of public health programmes there is always a danger of an overemphasis on assessment and evaluation. As Jelliffe and Jelliffe (1) have recently stated, sometimes a compulsive insistence on scientific investigation can delay proof of the obvious and thus impede the introduction of necessary preventive measures. The reason we have to concern ourselves with assessment, however, is that resources are becoming increasingly limited, and it is necessary to know what we have achieved and what we have failed to achieve. Assessment criteria may conveniently be discussed under four headings: mortality, morbidity, growth, and finally, indices based on functional capacity.
8.2. Mortality rate, particularly infant mortality rate, is one of the classical public-health indices, and the one-to-four-year age-group mortality rate has frequently been used in comparative international surveys as an index of the prevalence of undernutrition in different countries (2). Internationally there is evidence of quite dramatic decreases in infant and pre-school mortality rates in recent years (3); measures of population dynamics are always more revealing than single assessments of mortality. To be realistic, however, it will be some time before there are completely reliable statistics for most developing countries, but even quite simple retrospective studies on relatively small samples can be valuable. Mothers can be asked questions such as, "How many children have you had, how many are still alive, and at what ages did they die?" Demographers have developed techniques for converting this level of information into more conventional statements about infant and child mortality.
8.3. In the interpretation of mortality data it is obviously important to take into account the cause of death. In the Gambia, for example, McGregor has shown that prior to 1973, 50 per cent of rural children had died before the age of five years (4). In Guatemala, by contrast, the corresponding figure was only about 25 per cent (5). This difference does not seem to be related in any significant way to dietary intake, and it would seem reasonable to speculate that the high mortality rates encountered in Africa might be related to infection, particularly endemic malaria, just as much as to food shortage. The relation between nutritional state and malaria is complex; both adversely affect total immune competence. Whatever the reason, it does emphasize that mortality as an indicator of nutritional status can be a very blunt instrument without additional knowledge concerning specific causes.
8.4. One also needs detailed information about the age at death. In the context of this report it is especially relevant to examine the distribution of deaths during the first year of life. The PAHO survey in Latin America and the Caribbean (6) showed than in most of the areas studied, about twice as many deaths occurred between one and six months as between six and twelve months. Figure 19 (see FIG. 19. Mortality from Nutritional Deficiency, Protein Malnutrition, and Nutritional Marasmus by Month of Age in the First Two Years of Life in 13 Latin American Countries Combined (Source: ref. 6)) gives the summary for the 13 Latin American projects combined. This finding is important, as it does not follow the predicted pattern if inadequacy of breast-milk and the introduction of contaminated weaning foods are the major aetiological factors in this high infant mortality. The PAHO data show that the distribution of deaths within the first year was the same whether the children were breast-fed or not.
As a further illustration of the importance of considering infection as well as diet in the interpretation of infant mortality rates, the findings of Martorell from Santa Maria Cauqué, Guatemala (7) on the age-incidence of diarrhoeal illness are important. The peak morbidity occurs between six and twelve months, i.e. after the peak of mortality, suggesting that weanling diarrhoea is not the major cause of the high infant mortality. On the other hand, Mata (8) in more recent studies in Costa Rica, has shown a very clear relationship between infant mortality rate and deaths from diarrhoea (see FIG. 20. Correlation between Infant Mortality and Diarrhoeal Disease in Costa Rica, 1965-1976 (Source: ref. 8)). Whatever the explanation for this difference, it is obvious that a proper assessment of the need for, and the adequacy of, different public-health measures, including dietary intervention, cannot be made unless one understands the natural history and causal relationships involved.
8.5. To get an accurate estimate of the incidence and severity of diseases that may be related to nutritional state is obviously difficult; diarrhoeal disease is the condition that has received most attention in so far as the young child is concerned. For a reliable check on incidence, observations really need to be made on the population sample at least every two weeks, and if the cause is also to be determined, this becomes a highly skilled and formidable undertaking. Interpretation can be complicated by large swings in seasonal incidence, as observed in the Gambia, Nigeria, and Nepal. Figure 21 (see FIG. 21. Incidence of Diarrhoea in Northern Nigeria According to Season (Incidence is Number of Attacks per Child per Three Months) (Data by courtesy of A.M. Tomkins)) shows differences in attacks for diarrhoea in the wet and dry seasons in Malumfashi, northern Nigeria, by age. We also need to know not only the frequency of episodes of infection but also their duration, which is an important indicator of severity. Both Mata in Costa Rica and Tomkins in Nigeria have shown that the duration of an infection is much longer in a malnourished, than in a well-nourished, individual, even though the number of episodes may have been very similar.
It is only fair to conclude that, although a reduction in morbidity, particularly from diarrhoeal disease, could be a very relevant indicator of the success of a maternal-child intervention, because of the number of variables and the resources required, the approach is more suitable as a research tool than for the routine assessment of a public health programme.
Anthropometry of the Child
8.6. Much has been written about the assessment of nutritional status in infants and young children by anthropometry. The usual cross-sectional approach is, however, relatively insensitive to change unless it is dramatic.
More precise information can be obtained by measurements of growth velocity. This naturally requires longitudinal measures, but the advantage is that quite small samples can give meaningful results. Figure 22 (see FIG. 22. Weight Gain in Children Aged 5-32 Months in Nepal during Two Monthly Periods (Mean ± SE) (Source: D. Nabarro, unpublished data)) shows seasonal difference in growth from the village of Dhankuta in Nepal; the sensitivity of growth velocity is obvious.
As already emphasized in relation to mortality and morbidity, it is important to look separately at children in different age-ranges and not to group them all together. There is an additional reason for this in anthropometric assessment. In most populations the prevalence of wasting decreases after the first two years, while that of stunting increases (9); it is thus not possible to interpret the response of three-year-old children in the same way as one-year-olds.
8.7. More information is needed about the significance of growth deficits. An important indicator is increased risk of death. Figure 23 (see FIG. 23. Mortality Rate in Relation to Weight for Age in the Punjab, India (Redrawn from Kielman and McCord) (Source: ref. 11)), from studies in the Punjab (10), shows the relationship between risk and degree of deficit in weight for age. The risk increases steeply with increasing deficit. A point, however, which has not been sufficiently emphasized is that for a given deficit the risk is much greater for younger children. Consequently the threshold or cut-off point at which the extra risk is appreciable varies with age. Below one year the threshold is at about 80 per cent of standard, between one and three years at about 70 per cent.
A very important study in Bangladesh (11) has traced the relationship between risk of death and degrees of wasting and stunting. Children who were severely wasted and stunted had very high mortality rates, but moderate degrees of stunting did not carry any extra risk.
8.8. Mortality is a very crude and extreme indicator of functional impairment. Since in some countries up to 50 per cent of pre-school children may be classified as stunted by the usual criteria (height-for-age less than 90 per cent of reference), it becomes extremely important to know more about the cause and significance of stunting. Does being small matter?
Some workers look upon stunting as a successful adaptation to a shortage of food, although not successful enough for the child to overcome completely the changes in his environment. This issue is of more than intellectual interest. There is no use in having an indicator unless it is useful for making decisions. The usefulness will depend on the type of decision to be made. If the decision is about the need for a feeding programme, then our ignorance about the causes and physiological significance of stunting is embarrassing.
Anthropometric Status of the Mother
8.9. To safeguard the nutritional health of women during their reproductive age, it is important to consider pre-pregnant status as well as that during pregnancy and lactation. The most meaningful measurements are weight-for-height and thigh circumference. The various skinfold measurements, such as triceps, biceps, subscapular, and pert-umbilical, may also be of value, although whether these provide clinically relevant information, not given by weight-for-height alone, is open to question and needs to be clarified. In countries where kwashiorkor is the major form of protein-energy malnutrition, the measurement of plasma albumin is important, as is blood haemoglobin where there is anaemia.
During pregnancy the most relevant anthropometric measurement is the amount of weight gained during its course. For the United Kingdom the recommended amount is 12.5 kg (12), and it would be considered undesirable if the mean increment for a population fell below 10 kg. This is a level of performance rarely achieved by poor women in the developing world. Research is desperatly needed in which anthropometric change is quantitatively related, both to the health and well-being of the mother, as well as to the success of the pregnancy and the subsequent growth and development of the baby. This work is necessary for the definition of health targets relevant to health planning in the Third World.
The biochemical measurements listed in the previous paragraph can be of even greater importance during pregnancy. For example, protein deficiency may compound the fall in albumin concentration that normally accompanies pregnancy because of haemodilution. Plasma amino-acid patterns can also be informative, but this is a subject for research; such measurements could not be recommended for public health programmes at the present time.
Babies' birth-weight, height, and head circumference relative to gestational age at birth are crucial parameters. Birth-weights in poor economic circumstances in the developing world are much lower than in Europe and North America, but this cannot be solely attributable to dietary deficiency since infections like malaria can profoundly affect birth-weigh/(13). The proportion of children born with a weight below 2.5 kg is a particularly relevant statistic because neonatal and infant mortality rise sharply below this point. In research programmes, placental weight is also an important measurement.
Assessment of maternal nutritional status during lactation is more difficult. Weight is normally lost during lactation at a rate of 570 g/month (14), but, as described in section 3.2, considerable metabolic adaptations occur and excessive weight loss is not observed unless food intake is exceptionally low. An important measurement is the baby's milk intake, although there is a wide normal range, and at an individual level only values below 500 ml/24 hr between one and five months of age can definitely be considered inadequate: however, a population mean volume of 650 ml would be considered low. As with bodyweight, it is apparent that considerable metabolic adaptation protects milk supply against the worst effects of dietary deficiency. For lactating women it is likely that assessments of overall health and well-being plus her capacity for an active life are likely to be the most revealing.
8.10. There is one final type of measurement of great potential value: measurement of functional capacity, an obvious example being the level of physical activity. Thomson(15), describing trials organized in the United Kingdom by Boyd Orr and others in the 1920s to test the effect of giving milk to school-children, wrote: "Acceleration of growth was confirmed and clinical examination of the children and reports from teachers suggested that the milk-fed children had improved in general condition and became much more alert and more boisterous and difficult to control than others." The difference in height growth between supplemented and unsupplemented children in this trial was 6 mm/year, but the difference in activity was likely to have been of much greater importance.
A reduced level of activity in children consuming inadequate but not disastrously low amounts of dietary energy has also been reported among rural children living in Uganda (16). Studies at INCAP in Guatemala (17) have likewise demonstrated that energy intake of pre-school children can be reduced from 90 to 80 kcal/kg without affecting nitrogen balance or growth, but this is only possible because of a reduction in energy expenditure.
Activity is an even more relevant functional parameter for pregnant and lactating women, as they represent an important component of the labouring work-force, particularly in rural areas of the developing world. As discussed in section 1.17, studies in Sri Lanka have demonstrated that iron supplementation enables work output to be increased. Investigations into work capacity and energy output need to be designed with imagination and flexibility; however, it is possible for a woman to complete the same task with a minimum of extraneous effort or with more joie de vivre. It is not unreasonable to suggest that the latter style of working provides a greater sense of well-being and general happiness. In the Gambia the unanimous first reason given by pregnant and lactating mothers for the popularity of the biscuit supplement (see section 3.26) was that it gave them more "power" for work. Since there is, as yet, no evidence that they were doing more actual work, it can only be concluded that this statement means the mothers were better able to work well within their capacity rather than at the extreme limit.
It is quite apparent that the use of functional tests is a subject that merits a much greater research input. Quite apart from their intrinsic physiological interest, it would enable the merits of nutritional intervention programmes to be translated into terms relevant to national development planning. They might be taken more seriously by politicians and government officials than would more medical and biochemical measurements whose significance is less obvious.
Nutritional Indices as Measures of Social Development
8.11. All the types of indicators discussed can be useful as long as their limitations are appreciated. They can be used for the obvious direct purpose of assessing the effect of interventions on nutrition and health, but also as indirect indicators of social development. An example of the latter use is a large-scale integrated rural development programme currently being funded by the British government in Nepal, in which there are inputs from agriculture, animal husbandry, forestry, irrigation, and education as well a health. The concept of using nutritional status indicators for this purpose has been accepted enthusiastically.
To maintain this enthusiasm, however, and to provide the governments of both nations with meaningful information, it will be necessary to establish an appropriate methodology in which data will be collected on a continuing basis and, of equal importance, whose results will be analysed and made available quickly so that necessary changes in the overall programme can be made when necessary.
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