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Introduction
Experimental design (I: Scrimshaw et al., 1967a)
Results
Collateral studies
Discussion of results
Medical, social, and public health benefits of the study
References
Notes
Nevin S.
Scrimshaw1 and Miguel Guzmán2
In the 1950s there was
still only limited recognition that malnutrition is often
precipitated by episodes of infection and that malnourished
children are more susceptible to infection, a synergistic
interaction. The Institute of Nutrition of Central America and
Panama (INCAP) was established in 1949 and immediately began
studying factors responsible for the high prevalence of
protein-calorie malnutrition, including kwashiorkor. It was
observed that almost every case of kwashiorkor was precipitated
by antecedent infections (Béhar and Scrimshaw, 1960), and that
the more malnourished children had infections of greater
frequency and severity.
As in most developing countries, the officially reported causes of the high mortality of infants and preschool children were incomplete and inexact. Deaths in which malnutrition is the direct or the underlying cause were almost entirely misinterpreted and usually did not appear in the official statistics. For example, during 1956 and 1957 the causes of the 222 deaths among children zero to four years of age in four Guatemalan villages, including one (Santa Catarina Barahona) selected for the current study, were reviewed by visiting the household immediately afterwards (Béhar et al., 1958). Forty of the deaths occurred with clear signs of kwashiorkor, 42 with respiratory infections, and 37 with diarrhea! disease. The official records indicated only one death from malnutrition, and the kwashiorkor deaths were all ascribed to Ascaris. However, it was also apparent that without the impact of infections there would have been few or no cases of kwashiorkor. Moreover, few children would have died from an episode of infection had they been nourished sufficiently to have normal resistance to infectious disease (Béhar et al., 1958). This was subsequently verified by the study of Puffer and Serano (1975) who investigated both the reported and underlying causes of death in children in Latin American cities.
Information on the frequency of infections and of malnutrition is even more unreliable. In general, however, their incidences are high in the preschool years, particularly during the first two years of life. In Guatemala breast-feeding commonly extends to 24 months, but beyond six months it no longer provides the protein and calories needed for satisfactory growth and development. In developing countries such as Guatemala, a weaning child is particularly vulnerable to acute diarrhea because of exposure to an unsanitary environment, lack of acquired immunity, and decreased resistance because of malnutrition (Gordon, 1964). Both malnutrition and diarrhea peak in the 6- to 24-month age span, with the process of weaning as a common factor (Scrimshaw, Taylor, and Gordon, 1968). Accordingly, excess morbidity and mortality among preschool children results from the synergistic impact of both malnutrition and infections
The national medical service, to the extent that the population was reached by it, provided only limited curative and almost no preventive medicine. The demand from the population and most of the physicians in the health service was for more curative services. Yet clearly curative medicine could neither correct the malnutrition associated with weaning nor prevent the occurrence of infectious diseases sufficiently to restore normal growth and development to young children. In this situation, INCAP sought funds for an investigation that would compare the effects of enhanced curative medicine, nutritional improvement, or both on the health of preschool children as compared with only the usual government health services. Funds were approved in 1958 by a Study Section of the US National Institutes of Health, with some limitations.
As approved, the design tested two basic assumptions:
1. That improved nutritional status of preschool children resulting from daily supplementation would reduce the incidence, severity, and duration of diarrhea! disease and respiratory disease, and other complications of the common communicable diseases of childhood and improve growth and development.
2. That good medical care would reduce morbidity and mortality from infectious disease and thereby improve growth and development in preschool children.
Malnutrition develops slowly over time by progressive deterioration of nutritional status. For this reason, cross-sectional surveys for assessing prevalence are not appropriate for answering these questions. Similarly, the significance of infection does not depend on a single acute event but relates to a progression of events. Only a long-term field investigation of a population in its natural environment, with follow-up of illnesses and periodic appraisals of nutritional status, is appropriate for the study of the interrelationships between malnutrition and infection. Association can be documented by longitudinal studies without establishing cause-effect relations. However, for confirming causation, appropriately controlled intervention trials are necessary.
Ideally,
randomly selected individuals should be assigned to each
intervention, but given the nature and complexity of the
interventions for this investigation, such an approach was not
practical. The only practical alternative was allocation of
interventions to different, but closely comparable, communities.
With this design, comparison of morbidity in the feeding and
control communities provided a basis for testing the hypotheses.
Similarly, the nutritional benefits resulting from the reduction
in infections were assessed by comparison of the nutritional
status in the three communities. Complementary observations
collected during the field study allowed identification and
evaluation of contributions from broad ecological factors
inherent in the cultural patterns and environment of the study
communities.