To analyze the factors associated with children's linear growth, according to the different subsystems of the 6Cs model and Bronfenbrenner's Bioecological Theory.
Data sourcesNarrative review, carried out in the Scielo, Lilacs, Pubmed, and Science Direct databases, based on research using the terms Bioecological Theory, child growth, and risk factors, combined with the use of Boolean operators.
Summary of findingsAccording to the 6Cs model, proposed based on Bronfenbrenner's Bioecological Theory, the determining factors of children's linear growth are in six interrelated subsystems - cell, child, clan, community, country/state and culture. The empirical studies included in this review made it possible to analyze protection and risk factors within the subsystems. Among the protective factors: are adequate birth weight and satisfactory weight gain, breastfeeding for six months or more; proper hygienic habit of hand washing, proper elimination of feces, and access to clean water. As risk factors: low, birth weight and size, prematurity, multiple deliveries, short interval between deliveries, non-exclusive breastfeeding until the 3rd month, frequency and severity of infectious processes and anemia, little parental education, short maternal statur, inadequate maternal nutritional status, domestic violence, family poverty, food, and nutritional insecurity, living in rural areas or at high altitudes.
ConclusionChildren's linear growth is determined by interrelated factors that encompass aspects prior to the child's birth, as well as socioeconomic, political, family and community issues.
The inseparability of growth and development processes is a widely recognized fact. Both are complex phenomena, which depend on the interaction between genetic potential and environmental factors. Regarding linear growth, there is a consensus that environmental factors are the main factors responsible for height variations between individuals from different populations.1,2 Different theoretical-conceptual approaches encbetween nature and environment. Among these, Urie Bronfenbrenner's Bioecological Theory stands out, which integrates genetic, biological, and environmental factors.3
Based on this theory, Harrison et al.4 proposed the 6Cs Model, composed of factors distributed in six interrelated subsystems: cell, child, clan, community, country/state (country) and culture. This model was initially proposed for the investigation of factors that contribute to childhood, obesity; considering its scope, however, it has been adapted to other complex problems that require a systemic approach.
Although a number of studies in the literature have sought to investigate factors associated with children's linear growth, it is important to analyze this phenomenon, including environmental factors, which expands the understanding of the interaction between the components involved. Thus, based on Bronfenbrenner's Bioecological Theory and guided by the 6C Model, it is necessary to consider that children's linear growth reflects the socioeconomic and cultural conditions of a community. Therefore, the evaluation of the systemic and interrelational character of the factors that are related to it is important for the definition of strategies that aim to minimize inequalities between people. The proposed study of child stature from the construction of a bioecological model, whose outcome is the linear growth of children and influenced by the Harrison Model4, may open a promising field to understand central issues in the prevention and treatment of growth retardation in children. There is no doubt that the task is challenging, mainly because it implies applying systemic and contextual thinking in research practice and intervention.5
This review, then, was based on a brief conceptual summary of the Bioecological Theory and the 6Cs Model, and reports of empirical studies that analyzed determining factors in the linear growth of children from the perspective of the 6Cs Model.
MethodsData sourceThis is a literature review carried out from April/2022 to June/2022. The search strategy comprised the use of these descriptors, in Portuguese and English: Bioecological Theory, child growth, and risk factors, combined with the use of Boolean operators AND / OR, to expand the search in the Scielo, Latin American Literature in Health Sciences (Lilacs), Pubmed and Science Direct databases.
The inclusion criteria were empirical studies that aimed to explain children's linear growth, evaluated by the height-for-age anthropometric index, from an ecological point of view, with analyses of possible factors that could interfere with this outcome.
Data synthesisData referring to author/year, objective, methods and main results were extracted. For the description and interpretation of the results, the information was grouped under the perspective of the 6Cs Model. Finally, an explanatory model was elaborated, making a synthesis of the current state of knowledge.
Bioecological theory of human development and the development of the 6C modelBronfenbrenner proposed a theory and a model that avoided the fragmented approaches to the study of human development, each level of which focused on a level of analysis: only the child, only the family, only the society.5 The first theoretical model, outlined in 1979, called “ecological”, highlighted the environment as the fundamental factor for understanding how the individual develops. In 1992, the approach became a little more detailed, contemplating aspects of development linked to the person, and was named “Theory of Ecological Systems”.6 Later, the theory envolved and the understanding of human development began to contemplate a more complex model, broader, considering four interrelated aspects: the process, the person, the context and the time (PPCT Model). In this more advanced perspective, the focus shifted to the individual, considering the dimension of time and the interaction between the person and the context in which he/she is inserted. These adjustments led to new denominations: the “Bioecological Theory of Human Development” and the “Bioecological Model of Human Development”, which defined the subsystems where the developing being is inserted.3,5,7
This PPCT process is highlighted as the main influencer of development and has to do with the reciprocal interactions that happen gradually, in terms of complexity, between the individual and others, and between objects and symbols present in their immediate environment. Regarding the person, Bronfenbrenner recognized the relevance of biological and genetic factors in development and paid special attention to personal characteristics that could contribute to the socialization of the individual.6
The context is characterized by any event or condition outside the organism that can influence or be influenced by the developing person, and is classified into four subsystems: microsystem, mesosystem, exosystem and macrosystem, socially organized, which help to support and guide the being in growth. These subsystems are arranged to describe and analyze the life contexts, proximal and distal, of human development.6,7
The microsystem, considered as the gravitational center of the biopsychosocial being, is the environment where face-to-face interactions take place. This level is extremely important, as it is where neighborhood relationships and family relationships occur, especially mother/child, which are crucial in child development.7
The contributions of Urie Bronfenbrenner and his PPCT model to the understanding of human development are based on the fact that his assumptions were able to reformulate the study of the development, where the developing individual is seen in a dynamic interaction with the multiple contexts in which he/she is inserted, that can directly affect their biopsychosocial well-being, as represented by Figure. 1.
Taking into account the breadth and complexity of the model presented, the need to consider the influence of each subsystem on the development of the individual becomes evident; clearly, this thinking is limited linear and unicausal. For the factors that determine a child's healthy development, in addition to innate biological conditions, it is necessary to think about the influence of family, community, and broader aspects of the socioeconomic and political situation, without losing sight of the temporal and historical transformations of each of these contexts.8,9
The 6Cs model proposed by Harrison et al.,4 based on Bronfenbrenner's systemic theory, explains the interaction of different factors; this model is composed of six subsystems, which in the description of the graphic model are called spheres: cell, child, clan, community, country/state and culture. In the cellular sphere, genetic and biological factors are included. The child sphere includes personal and behavioral characteristics. The clan sphere, in turn, includes family characteristics, such as parental dynamics and domestic rituals. Peers, schools, and other institutional factors and community factors are combined into a single sphere called community, which represents factors relating to the child's social world outside the home. In the country sphere, state and national institutions are included that influence citizens' priorities and restrict their opportunities. Finally, in the sphere of culture, culture-specific norms, myths and prejudices that guide the fundamental assumptions of citizens and policymakers about food, exercise, health and the body are considered.4
This model does not focus just on individual factors in the understanding of growth and development processes; it recognizes the importance of environmental factors and context for the explanation of phenomena. From the revised articles (Table 1), a model was constructed having the linear growth of the child as outcome, based on the Harisson et al.4 Model (Figure. 2).
Studies on determining factors of children's linear growth.
Although there are several studies in the literature that explore factors associated with children's linear growth, the systemic approach, by allowing the visualization of possible interactions between the various factors that make up the subsystems, facilitates understanding of the phenomenon and, thus, makes it possible to determine where interventions at different levels - cell, child, clan, community, country/state and culture - can be effective in promoting adequate child linear growth.4
Figure. 2 illustrates an explanatory model for the determining factors of children's linear growth, according to the six subsystems defined by Harrison et al.4 It is possible to visualize, then, protection and risk factors that are interrelated within the subsystems - cell, child, clan, community, country/state and culture.
At the cellular level, processes coordinated and strongly orchestrated by the fetal genome (sum of maternal and paternal genomes) and modulated by the cellular microenvironment (gene-environment interaction) influence the normal growth and development of the fetus, including its organs and tissues. The cellular microenvironment is determined by the fetal environment, which, in turn, is determined by the maternal and external environments, so the environmental issue will reflect on the biology, physiology and metabolism of the newborn.10
The intrauterine environment aggregates cellular factors that can influence later growth and development of children. The pre-gestational nutritional status and maternal nutrition during this phase can influence the health conditions of the fetus, such as birth weight. Deviations in birth weight are related to increased child morbidity and mortality and should be evaluated early.11 In the studies found, low birth weight was one of the variables most related to growth retardation, demonstrating its influence on future child growth.12–20
Other conditions related to pregnancy that influence child growth and development are prematurity21, small size at birth, multiple births22,23 and shorter birth intervals.20,24 A single study found gestational factors that protected adequate linear growth were satisfactory birth weight and weight gain.25
The characteristics inherent to the child include sex and age and behavioral characteristics, such as history and duration of breastfeeding, minimum acceptable diet both in adequate diversity and frequency, in addition to the history of infections.
Sex is a biological factor that interferes with nutritional status, determining growth and differentiated energy stock between females and males, that is, lower linear growth and energy accumulation in the form of fat for girls and greater linear growth and greater protein supply for boys.26 Thus, male children, because they have a higher protein-energy need than female children, are more subject to the development of short child stature, when the food supply is similar. Therefore, being a boy is a risk factor for children's linear growth.18,22,23,27,28
Regarding growth and age, some articles 27–30 have pointed out that age younger than 24 months is a risk factor for child growth, considering the fact that children under 2 years old have a high growth rate and, therefore, greater nutritional needs. Nshimyiryol et al.18 state that age between six to 23 months and 24 to 59 months is a risk factor for developing short stature. This is because, when for some reason growth in early childhood is slow, the nervous system permanently “programs” itself to save energy, to ensure survival in adverse conditions, with adaptations including hormonal ones. After this phase, these adaptation mechanisms have already occurred and older children, who depend more on hormonal regulators, are able to make the most of the energy saved.31
With regard to dietary characteristics, breastfeeding is recognized as the ideal form of infant nutrition, especially in the first months of life. Children who are breastfed are healthier and have better cognitive development.32 On the other hand, non-exclusive breastfeeding in the first six months of life is a risk factor for inadequate child growth.33
Four studies identified similar relationships. Rachimi et al.,15 Garcia Cruz et al. 17 and Ayelign & Zerfu23 point to breastfeeding for six months or more and its early onset as protective factors for adequate linear growth; Musaad et al.34 reveal non-exclusive breastfeeding up to the 3rd month and Sk et al.20 the short duration of breastfeeding as risk factors for short child stature.
After breastfeeding, at food introduction, when food supply is insufficient early in life, adaptations for survival occur through saved energy, selectively preserving some tissues and organs over others. This adaptation is achieved by endocrine changes that affect growth, energy expenditure and body composition, which are influenced by the composition and quantitative and qualitative content of the diet.31,35
Some studies included in this review identified an association between low dietary diversity and short child stature,29,30,36–39 as well as the time of initiation of complementary feeding was related to stunting, 17 indicating that in families that do not have a minimum diet acceptable in terms of adequate diversity and frequency, children are more likely to be stunted.
When taking into account the child's health status, the frequency and severity of infectious processes, as well as the occurrence of anemia, are related to child growth, as increased metabolism requires a greater protein energy supply; protein insufficiency was confirmed by three articles found in this review.39–41
Starting from the environment where children develop, the context in which the proximal processes associated with child development occur is the family. A harmonious family environment and the role of the support network have already been attested as protective effects against the consequences of poverty and social vulnerability.42 The family, even experiencing an unfavorable context, has a crucial importance in child development, responsible for ensuring the children a healthy eating pattern and provide a stimulating psychosocial environment, indispensable for their full growth and development. Maternal height and nutritional status influence the linear growth of offspring. These influences likely comprise both genetic and non-genetic factors, including nutrition-related intergenerational influences, which have an impact on growth, making it difficult to achieve the genetic potential for maximum height in low- and middle-income countries.43
Thus, with regard to maternal characteristics that influence child growth, maternal and even parental education13,15,17,18,20,22,23,25,27,30,36,38,41,44–46, mental health in the prepartum period, in addition to maternal age38,47, occupation17,20,28, short stature and maternal nutritional status12,13,15,18,19,25,36,38,44,46,48–50 are factors that are directly related to children's linear growth, as confirmed by the studies found in this review.
Family size is also important, especially related to social vulnerability, as scarce resources are shared by more members. Another influential factor is whether this family is headed by women or men, as the mothers' decisions take into account factors that the fathers do not.13,17,30,51 The presence of violence in the family also influences child growth, as the family structure at these times is weakened.52
In order to broaden horizons beyond the family environment, it is important to emphasize that children's linear growth reflects a multicausal process that is influenced by environmental, social and biological factors.53 In this process, among the contexts that represent the environment, is the community where the child interacts with others outside the family. Therefore, the characteristics of the sanitary conditions of the community directly influence the development of this child. One review found consistent support in numerous previous studies showing that even children who are fed in sufficient amounts and are adequately breastfed, if exposed to intestinal inflammation caused by environmental enteric dysfunction, they will have their growth stunted.54
Recent articles demonstrate that environmental health conditions are associated with the development of environmental enteric dysfunction, and this in turn may contribute to inadequate infant linear growth, secondary to nutrient malabsorption, decreased immunity, and recurrent infections.55–58 These findings highlight the importance of appropriate environmental sanitary conditions as one of the pillars in promoting adequate linear growth in childhood. The distance from a source of water suitable for consumption can be a risk factor; 21 on the other hand, the proper hygienic habit of washing hands, adequate elimination of feces and access to a source of potable water are protective factors for satisfactory growth.44,59
Another important fact to be considered is for the families that have unsatisfactory socioeconomic conditions. Studies have already shown that the individual's height reflects the socioeconomic and cultural conditions of the child's community, with linear growth retardation due to nutritional/environmental causes being one of the most sensitive indicators of social inequality between peoples.31,60
Socioeconomic and demographic variables such as per capita family income, maternal schooling, access to consumer goods, number of rooms, number of people in the household and type of household have already been associated with insufficient linear growth in children.13,61,62 These characteristics are mediated. due to low purchasing power and low education, which leads to the acquisition and consumption of inadequate food.61,63
Studies have reported that when households and/or communities were considered poorer, there was a greater proportion of child growth retardation.13,18,21–23,36,64,65 This condition can lead to the acquisition and consumption of inadequate food, which can lead to food insecurity. This insecurity has also been associated with stunting in children.19,44
Still in the community domain, when expanding the spectrum of factors involved, housing in rural areas, living at higher altitudes, greater variations in rainfall and the experience of natural disasters can be considered as risk factors for the development of short child stature.15,65–69
When looking at the context of the economy, state and federal policies related to child nutrition establish parameters that influence community resources and practices. Community and social factors are the only elements under the contextual determinants of child linear growth mentioned in the World Health Organization (WHO) framework. Sub-elements include political economy, state and health care, education, agriculture and food systems, and water, sanitation and environment. Related to these sub-elements, linear child growth is associated with many determinants of political economy, state and health care, water, sanitation, and the environment.70
Thus, it has been shown that severe food insecurity was associated with growth retardation even in the post-harvest period 29 and that, in the political sphere, a prenatal care program, when not implemented, proved to be a risk factor.14,23 A policy of encouraging the purchase of food from family farming for school meals was seen to reduce the prevalence of stunting.71 These studies illustrate how broad the determinants of this problem are.
Finally, society and culture include beliefs and norms, social support networks, and key concepts often influenced by other levels such as the media and public policies governed by the state. In this context, it is important to promote adequate conceptions to provide healthy behaviors at the levels of community, family and individual. 7
Although, in the current review, no articles were found that related the extent to which cultural factors can interfere with linear growth, the lack of knowledge can be harmful. An example of that is the non-recognition of the problem that makes sense in a society where children with growth retardation are often offspring of parents with short stature, who, in turn, also had small parents, and this phenomenon is interpreted as a “family problem”. The population, in general, is unaware of the relationship between poverty, chronic hunger, inadequate nutrition, poor quality of life and inadequate linear growth.
ConclusionThis review showed that children's linear growth is determined by interrelated factors that encompass aspects occurring beforethe child's birth, associated with pregnancy and the mother, which reflect on the child, as well as issues of the family nucleus and the community in which the child is inserted, and also for socioeconomic and political issues. In this way, the articulation between the six subsystems was evidenced and a 6Cs model was developed for the determining factors of children's linear growth.
The English text of this paper has been revised by Sidney Pratt, Canadian, MAT (The Johns Hopkins University), RSAdip - TESL (Cambridge University).
