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Rollins School of Public Health at Emory University, Atlanta, GA 30322 and * Save the Children Japan–Vietnam Office, Hanoi, Vietnam
2To whom correspondence should be addressed. E-mail: watanabe{at}savechildren.or.jp.
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ABSTRACT |
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 TOP ABSTRACT SUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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KEY WORDS: • child development • growth • nutrition • Vietnam
In 2004 it was estimated that 162 million preschool children, or 33% of children < 5 y old in developing countries, were stunted [height-for-age Z-scores (HAZ)3 < –2] (1). The negative effect of malnutrition on child survival has been well documented. For example, children who are underweight have an 
2- to 8-fold higher risk of death than those who are better nourished (2). Malnutrition in early childhood impairs functional performance in adulthood; this impairment may be physical as well as cognitive. Economic losses due to the physical and cognitive losses are substantial. Malnutrition in childhood decreases intellectual potential and productivity in adulthood. Furthermore, physical losses in adulthood also have intergenerational effects on child health and nutrition (3). Improving the physical and cognitive development of children in lower-income communities will have far-reaching effects throughout the less-developed world. Effective program designs for nutrition and early childhood development need a clearer understanding of their effects on physical and cognitive development.
The negative effect of malnutrition on cognitive development has been demonstrated in multiple locations around the world. Some cross-sectional studies found associations between chronic malnutrition, marked by stunting, and poor cognitive function among school-age children (4–6). These studies include one in Vietnam, although it did not control for poverty. Other longitudinal studies showed that height-for-age during infancy was strongly associated with cognitive performance in late childhood (7).
The positive effect of nutrition interventions on cognitive development has also been shown. Several supplementation studies suggested the potential for greater cognitive development through improved nutrition at early ages in populations with endemic undernutrition (8–14). Although not conclusive, it is generally agreed the first 3 y of life constitute the most vulnerable period, one in which nutritional status is of particular importance (15). Several studies reported evidence of long-lasting benefits from early supplementation on cognition when the children reached school age (11,14). The benefits of supplementation during early childhood on cognitive development may not be apparent at school age, but they are present by adolescence through interaction between schooling and nutritional improvement (11,16).
What is much less documented, less well understood, and thus a subject of considerable, sometimes acrimonious debate, is whether adding an early childhood development (ECD) intervention, defined as preschool-based activities and parenting education, to a nutrition intervention in communities in which growth stunting is endemic can improve cognitive performance. Because a majority of the children served by existing ECD programs in many of the developing countries belong to the age group 1–2 y away from entry into primary school, the effects of ECD interventions for this age group should be investigated. Hence, the objectives of the present study were to assess the existence of and potential effects of an ECD project during the preschool years (ages 4–5 y) on the cognitive development of school-age children in rural communes in Vietnam where a nutrition project was implemented when the children were 0–3 y old.
We hypothesized that the cognitive development of children participating in the ECD project would improve more than that of nonparticipating children. Nutritional status and cognitive development of the children are often confounded by the household environment, such as economic conditions, age, and education level of the mothers; these were taken into account in our assessments.
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SUBJECTS AND METHODS |
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Save the Children Japan implemented a nutrition intervention using Positive Deviance Inquiry (PDI) for 2 y from 1999 to 2000 at 5 communes in Vinh Loc district, Thanh Hoa province, targeting all the children aged 0–36 mo in the communes. The PDI approach identifies successful child-caring practices of poor families who have well-nourished children (19). The intervention communes were selected on the basis of 4 criteria set by the implementing organization: high prevalence of child malnutrition, poor socioeconomic conditions, absence of prior or current participation in the national nutrition program, and the existence of leaders interested in the project. The main components of the nutrition intervention included bimonthly growth monitoring for all children and 9 sessions of a 12-d nutrition education rehabilitation program (NERP) conducted every month by local health volunteers in their hamlets, targeted for severely malnourished children [weight-for-age Z-score (WAZ) < –3]. Approximately half of the families participated in at least 1 NERP session, where they learned nutrition- and health-seeking behaviors and fed the children locally available nutritious foods. In addition, antenatal care services, home gardening, and a savings and credit program were promoted to help strengthen and sustain the nutritional benefits.
Of the 5 communes, 2 were followed up with an early childhood development (ECD) project for 2 y during 2002–2003, targeting children of preschool age (4–5 y old). The 2 communes were selected because they had less access to quality preschool services. Although the majority of the children aged 4–5 y in the 2 communes attended preschool at baseline, the attendance and the quality of preschool teachers in the 2 communes were lower than those in the other 3 communes. The ECD intervention strengthened existing center-based preschooling through material support and teacher training on child-centered teaching methods. It also supported parental behaviors through 1-d training sessions for fathers and mothers separately every month on 10 different topics concerning child care and development. In addition, the interventions included the establishment of a small local library for parents and promoted play corners in the homes of participating children.
Anthropometric measurements of height and weight were collected for all of the participating children in 3 surveys conducted in 1999, 2000, and 2001; at that time, mothers were interviewed about their behavior and knowledge of child care. The present study focused on primary school children living in the project communes who were aged 6.5–8.5 y in 2004 and were exposed directly to 1 or both of the 2 different interventions from 1999 to 2003.
Sampling. Two communes were selected as samples for this research and represent the 2 study populations. The first commune represents those populations exposed only to the nutrition intervention; the second commune represents those exposed to both the nutrition intervention and early childhood development. The main selection criteria for the 2 communes were similar socioeconomic conditions and ecologic characteristics. Baseline data on wealth ranking, ethnic composition, and ecologic characteristics collected from the district in 1998 were used to identify the sample communes. We studied nearly all of the children (431 of 474) listed in the sampling frame of children aged 6.5–8.5 y in the 2 communes. The sampling frame was established on the basis of the data collected in past surveys, which were updated by the most recent census records available at the Commune People’s Committees. The criteria for eligibility for the sampling frame were that the children had been living in the commune since 1998, were currently registered in the same commune, and were between the ages of 6.5 to 8.5 y.
Data collection. Standing height was measured to the nearest 1 mm with a standard technique that used the infant/child/adult height measuring board (Shorr Production) (20,21). The survey team was trained in anthropometry standardization exercises conducted by a senior program officer of Save the Children Japan, to avoid interobserver measurement bias.
Raven’s Colored Progressive Matrices test was used to measure the cognitive performance of the children. The test measures the ability to develop new insights and information from what is already perceived or known (22). This test was used to assess the cognitive ability of children in several international studies in developing countries such as Guatemala (11), Kenya, Egypt, and Mexico (5). The test generally has had high internal consistency and retest-reliability (>0.8); factor analytical studies showed that the test is a good indicator for Spearman’s g-factor (23). The standard version of Raven’s Progressive Matrices consists of 5 scales (A–E), with 12 items in each scale. Each item contains a figure with a missing piece, below which alternative pieces are placed to complete the figure. Each set involves a different principle for obtaining the missing piece; within a set, the items are arranged in increasing order of difficulty. According to the instructions given by the trainer, Raven’s Colored Matrices version was administered. The Colored Matrices version, consisting of 3 scales, Test-A (12 items), Test-B (12 items), and Test-AB (12 items), is designed to assess with greater precision the intellectual processes of young children (22). The same approach was taken in similar research conducted in Guatemala (11).
Because the test has not been standardized locally, interpretations of the scores were made only through comparisons of the group mean scores within the study population. Field workers administered the test one-on-one for each individual child, taking 15 min per test per child. A trainer, affiliated with the Research and Training Center for Community Development in Hanoi, conducted training on the test methods and use of materials made available by the Center for this research (24). To minimize examiner’s biases, children were assigned randomly to field workers, and no information was provided to the field workers regarding interventions, nutritional status, and socioeconomic level of children. The workers were trained repeatedly on skills and attitudes against biases throughout the test administration. The training included trial test administration, which confirmed agreement between the test results obtained by the workers and the trainer.
In addition, selected information was gathered on maternal characteristics (age, education, number of deliveries, occupation), household characteristics (number of children and family members, presence of grandparents in the household), and childcare (preschooling history) through interviews with mothers, conducted by field workers in Vietnamese. Data on household monthly income were collected from commune-level secondary data sources. A questionnaire was developed in English, translated into Vietnamese, and pretested in the field before revisions and completion.
The research team consisted of 16 field surveyors; 4 were assigned exclusively for the Raven’s tests and 2 for anthropometric measurements. They worked in 2 groups under the supervision of a team leader. Half of the field workers were recruited for short-term work as main surveyors from universities or nongovernment organizations, whereas the remaining workers were recruited from local partners as assistants to the main surveyors. They had previous experience with data collection in rural Vietnam and were trained in data collection techniques before doing field work. The field workers were assigned specific data collection tasks that were fixed throughout the duration of the survey to minimize interobserver errors.
Data management and analysis. Names and dates of birth of mothers and children were obtained from the demographic record book held in the hamlet and surveys conducted previously in the communes by SC Japan. Then they were cross-checked at registration points in the survey sites, double-checked by field workers before measurements were taken, and finally checked by the team leader after data collection. All data collection forms were reviewed by the team leader each evening and any discrepancies were discussed. Data collected in the field survey were entered into EPI Info 2000 (CDC) immediately after collection.
The 2 main outcome variables were HAZ and Raven’s test scores. Heights were compared with the international National Center for Health Statistics/WHO/CDC reference standards (25) and converted to HAZ using Epi Info 2000. Raven’s test scores were calculated by summing total correct answers across the 3 scales. All data were entered into Epi Info 2000 and analyses were performed using SAS 8.0 (SAS Institute) (26).
For data analysis, the present datasets were merged with the data of previous surveys, which included weight/height of children at earlier ages, household characteristics, and child feeding/caring practices of mothers. Bivariate analyses were performed using t tests for continuous variables and 
2 tests for categorical variables. The generalized linear model (GLM) was used to assess effects of interventions on HAZ and Raven’s tests scores. Similarly, generalized estimating equations (GEEs) were used to assess the effects on proportions. The GLM and GEE models control for potential confounders to compute adjusted mean scores and proportions of each effect group for comparison. P-values 
0.05 were considered significant.
Human subjects and ethical considerations. The project was approved by the Emory University Institutional Review Board before the present research was launched. Written consent was received from parents of the children who voluntarily participated in the research. Field workers were trained in ethical considerations and were under strict orders not to discuss information pertaining to subjects with members of the community or with other nonproject-related persons. All of the data collected in the research were kept confidential and used only for aggregated data analysis with anonymity.
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RESULTS |
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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2 children (95%). Mothers were young (mean age = 33 y) and their education level was low; more than one-third had completed only primary school. Farming was the primary occupation of mothers in the communes (97–98%); 23% of children lived with their grandparents. Most of the household variables were similar for the 2 interventions. They differed from each other, however, in maternal education (P = 0.05), child age (P < 0.01), parity (P = 0.02), and number of children (P = 0.01). The ECD-and-nutrition intervention commune had fewer children per household, they were younger, and their mothers had less education. Those variables were controlled for in multiple variable analyses.
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Finally, scores on the Raven’s tests were modeled with GLM to compare how changes in the nutritional status of children from baseline to 2004 affected cognitive test scores between the 2 interventions (Table 5). Nutritional status at baseline and in 2004 were cross-tabulated to form 4 groups: "drop" (HAZ dropped from >–2 to <–2), "remained stunted" (HAZ stayed <–2), "never stunted" (HAZ stayed >–2), and "catch up" (HAZ improved from <–2 to >–2). Adjusted differences in cognitive test scores between the groups were detected only for the nutrition-only intervention (P = 0.001–0.06). Mean scores from the 4 groups (Fig. 1) illustrate the dose-response relation between the change in nutritional status over time and cognitive test scores for the nutrition-only intervention commune, which was not present for the ECD-and-nutrition intervention.
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DISCUSSION |
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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Overall, the current level of stunting among school-age children who were exposed to the Save the Children’s nutrition program was 20% in terms of the proportion of children < –2 HAZ. Age-specific nutrition status by height-for-age is not available for this age group in Vietnam. A recent national survey reported the prevalence of undernutrition among children 6–10 y old as 27% nationally and 28% for rural regions (27). Although these data provide only an overview, it could be argued that nutritional improvement has occurred in these communes. The difference was not significant, however, between the 2 communes in terms of the amount of change over time in mean HAZ scores. Those results indicate that there were no additional effects of ECD interventions on the nutritional status of children.
With the nutritional improvement program, the nutritional change among children exposed to nutrition-only interventions had a linear association with cognitive development. This finding, consistent with other studies that detected significant associations between cognitive performance among school-age children and their current or early nutritional status (5–7,11), suggests that continuing malnutrition is detrimental to the cognitive development of children.
Children exposed to Save the Children’s ECD interventions had significantly better test scores than their counterparts who experienced only the nutrition intervention. Differences in test scores between stunted and nonstunted children were minimal among children who had ECD interventions, whereas they were significantly larger in the nutrition-only intervention commune in which better-nourished children had higher scores than malnourished children. Significant effects of the ECD intervention were thus most noticeable for currently malnourished children whose test scores were significantly higher than similarly malnourished children who were exposed only to the nutrition intervention.
Furthermore, additional analyses controlling for initial height, change in height over time, and their interactions did not alter the findings without the adjustments, suggesting that the effect of the ECD intervention was separate from the effects on physical growth. All of this evidence supports the protective effect of ECD intervention against the negative cognitive effects of growth failure; it is possible that the effects of Save the Children’s ECD intervention "compensated" for the loss caused by poor physical growth in the earlier years.
Reviews of early childhood development programs for children in low-income families in the United States reported evidence that the programs produced large effects on IQ during the early childhood years and sizable persistent effects on school achievement (28). Those included longitudinal studies, which found significant positive effects on IQ scores (29,30), achievement test scores (29–32), school repetition (29,32), attendance (33), and special education (29–31). For populations in developing countries with endemic undernutrition, many studies assessed the effects of food supplementation on the cognitive development of children. In contrast, very few examined the additional effects of psychological stimulation.
A longitudinal study in Cali, Colombia assessed the effects of integrated interventions of varying duration, consisting of nutrition supplementation, health care, and an early education program, on the cognitive development of preschool children aged 42–84 mo who were chronically malnourished. The results showed that nutrition supplementation alone before initiation of the preschool program had no effect on psychological development measured by various intellectual ability tests at several ages from 4 to 7 y, whereas the combined interventions of nutrition and early education had larger effects if they were started earlier and lasted longer (34). The study design, however, did not allow us to compare the effects of nutrition supplementation alone with the combined interventions of supplementation and stimulation. Another study in Bogota, Colombia compared the effects of supplementation only, stimulation only, supplementation and stimulation, and no intervention on cognitive development of children aged 0–36 mo. It detected clear effects of nutrition supplementation on the cognitive performance of children as measured by the Griffith test. However, no added benefits of psychological stimulation were found (12).
Evidence concurrent with this study’s findings was provided by a study of stunted Jamaican children, aged 9–24 mo, who were randomly assigned to nutrition-only, stimulation-only, nutrition-and-stimulation, and control groups (10) After the 2-y intervention, the benefits from a combination of supplementation and stimulation were additive, and the children receiving both treatments caught up to the nonstunted control group in developmental levels. A follow-up study of those children at 7 y of age showed small, but significant, global benefits of the interventions (9). That study indicated a plausible mechanism that the lower activity levels of undernourished children may not affect their development when they are in a stimulating environment.
The greater effect of the combined interventions in improving both physical growth and psychological development than the effect of either one alone may be explained by their interactions at 3 different critical points: at the child level, between the child and his or her family or caregivers, and in the design and delivery of programs (35). At the level of the child, the negative cognitive effects of growth failure were evident, as shown in the nutrition-only commune in this study, which was protected by exposure to the ECD intervention. Psychosocial stimulation programs, although improving cognition, would also have positively affected physical growth (36), which was not detected in this study. This was possibly due to the late timing of the ECD intervention (ages of 4–5 y). Effective timing and duration of ECD interventions warrant further investigation. As illustrated by similar studies in Colombia (32), the effects of psychological stimulations were larger if the interventions were applied earlier and for a longer period. A follow-up study on younger children aged 0–3 y at the time of this study, who were exposed to the ECD intervention at younger ages and for a longer period, may provide useful insights.
At the level of interaction between child and caregivers, better-nourished children tend to be more active and exploratory and more able to elicit parental interaction. ECD intervention may have stimulated parents to acquire more responsive behaviors toward malnourished children than parents with nutrition-only intervention. This study, however, cannot provide information to further examine the critical points due to lack of data on parental behaviors and child-parent interactions. It is of interest to determine which components of the ECD interventions worked most effectively on child-parent interactions. The ECD interventions combined the center-based approach with the parental support component, which cannot be separated in this study design. The preschool-based activities could have stimulated active learning and social interactions between the child and his or her environment, and the parental education component may have enhanced parents’ knowledge, attitude, and practices regarding child care at home.
The nonverbal cognitive ability measured by Raven’s Colored Progressive Matrices test is defined as "eductive," which refers to the ability to make meaning out of confusion. It is not within the scope of this study to detail the interpretation beyond the one summarized by Raven that eductive ability, compared with other cognitive abilities, is promoted when parents involve their children in their own attempts to make sense of difficult situations (37). This aspect of ability has relevance in assessing effects of ECD interventions. However, we can by no means assume that Raven’s progressive matrix is the single best tool with which to assess cognitive development in rural Vietnam. It would have been preferable to perform several other tests that have been used for different purposes in studies measuring children’s cognitive performance. School test scores and teacher ratings were of particular interest because the effect is modified by access and quality of education at preschool and primary schools. Nevertheless, the study provided a unique example of the utility of Raven’s tests in assessing the cognitive development of children in developing countries.
We acknowledge several other limitations to this study in addition to the points raised above. Unlike intervention trials using direct high-energy food supplementation or intensive provision of psychological stimulation, this study involved interventions designed for a real-life project with a primary focus on behavioral changes in feeding and child-care practices by parents as well as the community. The absence of data on the key behavioral factors did not allow us to investigate intermediate variables. If the Raven’s test had been conducted at baseline, it would have provided stronger evidence that the differences could be attributed to the ECD intervention. Larger samples randomly selected from the entire project communes would have provided a statistically more valid estimation of measurements. Measurements of potential confounders, particularly regarding educational opportunities available for children and mothers, would have helped to better explain study outcomes and interpretations. The optimal study design was beyond the resources of this study.
In summary, this study documented evidence that during a period of nutritional change, children who failed to catch up in linear growth are likely to lose the opportunity for cognitive betterment in the early primary school years if appropriate interventions are not given. The findings suggest that early childhood program interventions for preschool-age children (4–5 y) increase the potential for cognitive development, particularly for malnourished children, whose growth failure prevents proper cognitive development. All of these findings support the importance of an integrated program of nutrition and ECD to optimize the potential for holistic development of children in an equitable manner.
The Government of Vietnam, in collaboration with international donors, has initiated efforts to develop an effective integrated model of ECD and nutrition for preschool children. Save the Children is expanding its ECD program to have a wider scope with particular focus on the northern mountainous regions where people belonging to an ethnic minority live. These regions have fallen behind during the current trend of widening regional disparity, and children there suffer from chronic poverty and inferior access to health and education services, as well as food insecurity. Such a context allows these disadvantaged children to lose their chance for physical and intellectual development. It is here that the contributions from nutrition and ECD programs are expected to be most important. It is recommended, therefore, that the effects of the integrated nutrition and ECD interventions be examined further through community intervention trials.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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3 Abbreviations used: ECD, early childhood development; GEE, generalized estimating equation; GLM, generalized linear model; HAZ, height-for-age Z-score; NERP, nutrition education rehabilitation program; PDI, positive deviance inquiry; WAZ, weight-for-age Z-score.
Manuscript received 7 December 2004. Initial review completed 26 January 2005. Revision accepted 24 May 2005.
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TOPABSTRACTSUBJECTS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
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