3
Influences on Children’s Health

Children’s health is determined by the interaction of amultitude of influences, reflecting complex processes. We divide these influences into biological, behavioral, and environmental (physical and social) even though our model of children’s health views their effects as highly intertwined and difficult to isolate. This chapter provides a summary of published literature and a framework for understanding those influences.

OVERVIEW

Biological influences as discussed in this chapter include genetic expressions, prenatal influences, as well as biological constraints and possibilities created by perinatal and postnatal events plus prior states of health. Behavioral influences include the child’s emotions, beliefs, attitudes, behaviors, and cognitive abilities that affect health outcomes. Environmental influences are wide-ranging and include infectious agents, toxins such as lead and air pollution, and social factors such as loving interactions with caregivers, socioeconomic resources in the family and community, and peer relationships, segregation, racism, culture, the availability and quality of services, and policies that directly or indirectly affect these other interactive influences (see Box 3-1).

The role and effect of biological, behavioral, and environmental influences change as children grow. For example, a pharmacological agent like thalidomide is highly toxic within a narrow window during pregnancy but not afterward, an attachment to a caring adult is especially critical during infancy, and peer influences appear to grow steadily from toddlerhood through adolescence. Even within



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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health 3 Influences on Children’s Health Children’s health is determined by the interaction of amultitude of influences, reflecting complex processes. We divide these influences into biological, behavioral, and environmental (physical and social) even though our model of children’s health views their effects as highly intertwined and difficult to isolate. This chapter provides a summary of published literature and a framework for understanding those influences. OVERVIEW Biological influences as discussed in this chapter include genetic expressions, prenatal influences, as well as biological constraints and possibilities created by perinatal and postnatal events plus prior states of health. Behavioral influences include the child’s emotions, beliefs, attitudes, behaviors, and cognitive abilities that affect health outcomes. Environmental influences are wide-ranging and include infectious agents, toxins such as lead and air pollution, and social factors such as loving interactions with caregivers, socioeconomic resources in the family and community, and peer relationships, segregation, racism, culture, the availability and quality of services, and policies that directly or indirectly affect these other interactive influences (see Box 3-1). The role and effect of biological, behavioral, and environmental influences change as children grow. For example, a pharmacological agent like thalidomide is highly toxic within a narrow window during pregnancy but not afterward, an attachment to a caring adult is especially critical during infancy, and peer influences appear to grow steadily from toddlerhood through adolescence. Even within

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health BOX 3-1 Organization of Influences on Children’s Health Children’s biology Children’s behavior Physical environment Prenatal exposures Childhood exposures Home, school, and work settings Child injury and the provision of safe environments The built environment Social environment Family Community Culture Discrimination Services Policy a childhood stage, health influences can act in very different ways because of the differing cultural interpretations that families attach to them. While biology, behavior, and environmental categories are useful for organizing our discussion, it is important to understand that healthy development is not the product of single, isolated influences or even types of influences. Warm and nurturing parenting is an important family influence, but prematurity or visual impairment can make an infant unresponsive to a mother’s initial nurturing. Mothers may react with apathy or disinterest, which produces even more withdrawal on the part of the infant (Lozoff, 1989). While simplified schematics or models help to organize understanding of the influences on children’s health both during childhood and beyond, life is not as simple as these models suggest. One caveat should be kept in mind in reading through the following review of evidence. Few of the cited studies drew their evidence from randomized experiments. And few if any of the nonexperimental studies included all relevant variables in their data and analyses. Thus, the findings reported in these studies are likely to suffer from exclusion of potentially important categories of influences, so that the associations that are reported as being important may be due to their associations with a more important or equally important characteristic, or due to interactions with other types of factors so that their effect may be manifested

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health primarily or only in certain population groups. A related problem is that few of the cited studies include data that represent the whole population of children. Thus, the findings that are reported as significant may be significant only in the population studied or similar populations. Nonetheless, the committee found the evidence to be sufficiently compelling to warrant inclusion when there was a plausible, well-supported connection between the influence and health. Moreover, inferences about the relative importance of the variety of influences are heavily dependent on the nature of the theoretical models that underlie statistical analysis. If more proximal influences are mixed with more distal ones, they may appear to have stronger effects, even in situations in which more distal factors are operating on a multiplicity of proximal influences and therefore have cumulatively greater effect overall. Thus, future research should adapt more appropriate pathway techniques to help to sort out the patterns by which the influences interact to produce different states of health. Finally, the relative lengths of the following sections are not meant to signify the relative importance of the influences. For some, the prevalence is less well known than for others. From the viewpoint of influences on population or subpopulation health, the relative frequency of the different influences is at least as critical as the degree of the risk that they pose to individuals. Additional research is needed to refine understanding of the relative contribution of each of the influences and the relevance of each across a variety of social and cultural groups. CHILDREN’S BIOLOGY A child’s biology determines how physiological processes unfold and how organ systems adapt to outside influences. Biological response patterns, including responses to stress, novel situations, and primary relationships, can directly and indirectly influence other biological, cognitive (learning), and behavioral processes. The term “biological embedding” has been used to describe how the external environment influences and shapes the biological environment (including the central nervous system), which in turn changes the way the individual interacts with the external environment (Hertzman, 1999). Genes DNA provides the blueprint for life. The units of heredity, or genes, are specific sequences of DNA that code for proteins that affect the particular physiology and anatomy of an individual. All cells contain the full array of genes but, depending on the cell type, some are expressed while others are not; for example, certain genes coding for proteins in the retina are expressed in the cells of the eye, but not in the pancreas cells. Disruptions in genes can be caused by events before, during, or after conception and may produce disorders immediately or later in life. A parent can pass on

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health a defective or abnormal gene or set of genes, a malfunction can occur during combination of maternal and paternal DNA, or exposure to an outside substance or condition can occur after conception that alters the genes in the fetus. Physical and social environments (e.g., family, community, school, culture) interact with and influence these biological processes. Influences of Genes on Responses to Different Environments Classically, genes have been considered to be the “instructions” for building proteins, although it is clear now that they have other functions as well. A gene may affect health as a result of the interaction of its protein product with another aspect of a child’s biology. The combinations of these interactions may result in an enhanced, worsened, or inconsequential change in health status. For example, sometimes an alteration in the gene (i.e., mutation) is identified due to the presence of a particular disease state, or it can be deduced that an individual with the mutation has a high probability of developing a particular disease. Understanding the biological pathway of the disease and its interactions with other biological processes facilitates treatment options by modifying the causal path. In the case of Huntington’s disease, for example, the disorder appears to be in part mediated by glutamate excitotoxicity; giving patients a substance that blocks this effect (glutamate receptor antagonists) interrupts this pathway and may retard the manifestation of the disease (Ferrante et al., 2002). The influence of genes on health always exists in an environmental context; in the next sections we describe how genes affect behavior and the physical and social environments. Genes and Behavior. That genes affect behavior has been amply demonstrated in honeybees (Ben-Shahar et al., 2002) and higher animals (Ruby et al., 2002; Chester et al., 2003; Hendricks et al., 2003). Examples in humans are being rapidly discovered, including genes that influence the relationship between exposure to trauma and susceptibility to posttraumatic stress disorder (Stein et al., 2002), genetic polymorphisms that protect against alcoholism (Wall, Carr, and Ehlers, 2003), mutations that result in sleep disorders (Wijnen et al., 2002), and several genes that are associated with simple phobias (Gelernter et al., 2003). Genes and the Physical Environment. The physical environment includes ubiquitous agents (e.g., ultraviolet light, amino acids and sugars in the diet, noise, speech) and somewhat less universally encountered ones (e.g., loud music, medications, pollutants). Some genes result in poor outcomes following common environmental exposures (e.g., phenylketonuria with phenylalanine, galactosemia with galactose, xeroderma pigmentosa with ultraviolet light exposures). Individuals with these genotypes are likely to be affected by the disease because they have a high chance of being exposed to the physical environmental agent. In some cases, the physical environment can be modified to improve outcomes

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health (e.g., a phenylalanine-free or galactose-free diet may improve IQ, no sunlight or ultraviolet exposure may reduce skin cancers). There are also gene alterations resulting from uncommon physical environmental exposures that affect health. Examples include a higher risk of lung cancer in individuals lacking glutathione S-transferase mu who smoke (Perera et al., 2002) and noise-induced hearing loss in some individuals exposed to high levels of noise—the gene or genes in this case are just being discovered (Kozel et al., 2002). These genes are known as susceptibility genes. An example of a positive susceptibility gene to a physical environmental agent may be that for perfect pitch. It appears that individuals with exposure to music and a family history of perfect pitch are more likely to acquire perfect pitch (Alfred, 2000). Genes and the Social Environment. The identification of genes that confer susceptibility to adverse or beneficial responses following exposure to diverse social environments has only just begun. In one study, abused children with a genotype conferring high levels of neurotransmitter-metabolizing enzyme monoamine oxidase A expression were less likely to develop antisocial problems in adulthood (Caspi et al., 2002). The risk of developing alcohol abuse or dependence also appears to have both a genetic susceptibility and a family influence (Macciardi et al., 1999; McGue et al., 2001), as does the risk for relapse and poor outcomes with schizophrenia (Campbell, 2001). Characteristics of Gene-Environment Interactions The expression of certain genetic characteristics depends on the environment in which they occur. Thus, gene expressions that lead to a disease in one context may not lead to a disease, or may result in a different disease, in another context (Holtzman, 2002). Inheriting a single copy of the hemoglobin S gene makes an individual resistant to malaria (Aidoo et al., 2002). However, inheriting two such genes gives the individual sickle cell anemia, a severe disease. Outside of malaria-endemic areas, sickle cell trait, the inheritance of one copy of hemoglobin S, has no known adaptive benefit and may be maladaptive. A single cystic fibrosis gene has been postulated to be protective against diarrheal diseases such as cholera, conferring a survival advantage to individuals who carry one copy of the gene (Rodman and Zamudio, 1991). However, individuals with two such genes have cystic fibrosis, a severe disorder with altered pulmonary and gastrointestinal function. Other examples of genes with positive influence also exist in given environments. The gene or genes that confer protection from cancer (Gonzalez et al., 2002; Reszka and Wasowicz, 2002) have been described. Genes may confer susceptibility only during a specific span of time, referred to as a critical period. For example, 20 percent of children are extremely sensitive to thalidomide during a critical 15-day period from day 20 to day 35 of gestation, although the gene or genes responsible for this enhanced sensitivity have not yet

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health been identified (Finnell et al., 2002). Presumably there are narrow windows of rapid development throughout childhood, including puberty, but critical windows of sensitivity to disruption have not been adequately described (Selevan et al., 2000). The complex interrelationships between genetics and environmental stimuli are not clearly defined and are an active area of current research. Gene Expression Understanding of the genome has rapidly expanded the study of the ways in which genes interact with diverse influences (e.g., physical and social environments) to affect health. Expression of genes (the amount of the protein encoded for by the gene) has a profound influence on the health of the individual. Gene expression is determined by many factors, such as promoters, regulators, mutagens/carcinogens/teratogens, X-inactivation, message stability, rate of protein degradation, prior exposures, all of which are affected by the environment. Interactions between genes and the environment influence different physiological pathways and adaptation (Holtzman, 2001) and may lead to adaptive or maladaptive phenotypes. An interesting example is the hygiene theory of childhood asthma, which postulates that children living in hygienic, low-pathogen environments develop an imbalance between two types of immune cell classes (TH1 and TH2). Children with an imbalance of TH1 and TH2 are more likely to develop allergies and asthma when confronted with allergens. When children live in low-hygiene, high-pathogen environments, they develop a strong system of immune regulators (a balance between TH1 and TH2 cells), and they are less likely to develop allergies or asthma (Yazdanbakhsh et al., 2002). Children living on farms or in homes with at least two cats or dogs in the first year of life have been shown to have significantly lower rates of allergic sensitization tested at 6–7 years (Ownby et al., 2002). Healthy development depends on gene expression being responsive to changes in the environment. For example, the radical change in the environment at birth is responsible for changing the expression of genes to enable the baby to make the transition from intrauterine to extrauterine life. These include the production of proteins that close the ductus arteriosus (Kajino et al., 2001), alter lung liquid absorption (Matalon and O’Brodovich, 1999), produce barrier function in the skin (Harpin and Rutter, 1983), produce immunoglobulins, and alter gene expression in brain development. Thus, to be healthy, newborns must make profound changes in gene expression as they transition from intrauterine to extrauterine environments. Converging findings from genetics and molecular biology demonstrate that a host of internal and external signals can stimulate or inhibit gene expression, including subtle factors such as the light-dark cycle (Hegarty, Jonassent, and Bittman, 1990) and tactile stimulation (Mack and Mack, 1992). This pattern of contingency is now recognized as part of the normal process of development in

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health embryology and developmental biology, and there is a growing body of literature demonstrating how factors, including internal neural and hormonal events and external sensory events, activate or inhibit gene expression during individual development (see Davidson, 1986, 2001; Gilbert, 2000; Holliday, 1990). Body Stores Chemicals in the environment (air, water, dirt, dust, food) move into the body across such biological barriers as skin, lungs, and the gastrointestinal system. Exposure is considered to be contact of the agent with the biological barrier; following exposure, the agent crosses the barrier and is found inside the body (the internal dose). After uptake or absorption across the barrier, chemical agents (including drugs) are distributed throughout the body, metabolized, and eliminated (U.S. Environmental Protection Agency, 2003; Atkinson et al., 2001). The rate of elimination varies substantially for different agents; some are eliminated in a matter of minutes; others may be found in the body for years following exposure. The amount of chemical/biochemical/vitamin/mineral stored or measured in the body is called the “body stores” or “body burden” of that agent. The committee has adopted the term “body burden” in this report. Body burdens of a chemical or drug represent the amount of cumulative exposure and, in some instances, can be transferred to another individual (e.g., from a mother to the fetus or infant through the placenta or in breast milk). Body burdens can improve or harm health, based on their biological characteristics and presence during certain periods of development. Maternal body burdens of either lead or polychlorinated biphenyls (PCBs) impair the cognitive function of offspring if present during critical periods during fetal development (Gomaa et al., 2002; Lai et al., 2002). A body burden of lead in the bones of young children has been associated with poor social behavior (Needleman et al., 2002; Wald et al., 2001), poor cognitive performance or development (Lanphear et al., 2003; Rogan and Ware, 2003), and impaired pubertal progression (Selevan et al., 2003). The relative impact of body burdens varies with developmental stage. Relatively lower body burdens of organic mercury will reduce cognitive development in young children more than at older ages (U.S. Environmental Protection Agency, 2000c; National Research Council, 2000). Some body burdens can have positive impacts on healthy development. For example, maternal body burdens of folate during the early first trimester of pregnancy significantly reduce the risk of a baby with a neural tube defect (Wald et al., 2001). Adolescents with higher levels of folate also have a significantly decreased risk of juvenile hypertension (Kahleova et al., 2002), and adults with high folate stores appear to be at substantially lower risk of cardiovascular disease (Wald, Law, and Morris, 2002). Some body stores that are beneficial at lower levels can become harmful at higher levels: a baby’s appropriate body burdens of iron will improve cognitive outcome, but an inappropriately high body burden of iron

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health potentiates oxidative stress (Rao and Georgieff, 2001) or can cause iron overload disease. Low maternal or fetal levels of vitamin A are associated with developmental disease, as are high levels. The impact of some body burdens vary across time and, to be understood, must be assessed at different times. For example, a maternal body burden of PCBs causes exposure to both the fetus and to the newborn via breast milk. Body burdens at one time may also impact measures of health in later time frames. A child who has received treatment for Hodgkin’s lymphoma, increasing the genotoxic body burden, is at risk for secondary cancers (Hack et al., 2002). Early Programming While not without controversy (Huxley et al., 2002), there is a growing literature on the potential role of “perinatal programming,” referring to the processes in which specific influences during critical or sensitive periods of development can have lifetime consequences by altering metabolic pathways and other physiological systems. This appears to be a special case of the more general phenomenon of how environmental influences can be embedded in biology during critical and sensitive periods of development. In humans, the relationship between fetal growth, postnatal growth, and the risk of such diseases as hypertension, coronary heart disease, and non-insulin-dependent diabetes have been frequently studied (Bertram and Hanson, 2002; Barker, 1998). Both human epidemiological and animal experimental studies support the hypothesis that relative undernutrition in the fetus results in significant and relatively permanent changes in important physiological systems (Nathanielsz, 1999). Perinatal programming indicates that sensitive or critical periods of development may have lifelong effects and influence the development of chronic diseases later in life (Ingelfinger, 2003). However, it does not discount the potential effect of the external environment (Seckl, 1998; Ingelfinger and Woods, 2002; Falkner, 2002; Roseboom et al., 2001) in modifying the effects. Fetal undernutrition is believed to induce persistent changes in several metabolic pathways, but the exact mechanisms are only now being pieced together through a range of animal experiments and human measurement studies (Seckl, 1998; Barker, 1998). Because it is likely that events occurring at other times modify prior influences, there is a growing interest in understanding the predisease pathways and biological changes that occur prior to the recognition of a vast array of clinical outcomes. Currently many of these predisease markers are either below current limits of detection or produce changes that are not currently measured on a routine basis (Lucas et al., 1999; Keller et al., 2003; Ingelfinger, 2003). Examples of such programming during particular sensitive or critical periods of development are coming to light. For example, low numbers of nephrons are associated with hypertension, and it has been shown that individuals whose mothers experienced severe protein-calorie malnutrition during the third trimester,

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health when nephron development takes place, are most at risk of hypertension (Roseboom et al., 2001; Keller et al., 2003). Outcomes associated with programming early in life may also promote health. For example, rats receiving high levels of licking and grooming as pups are less fearful compared with rats that received low levels of licking and grooming (Francis et al., 2002). The mechanism for this change in behavioral programming appears to be the influence of maternal licking on gene expression during a critical period of development and subsequent changes in the development of synaptic receptor sites for specific neurotransmitters (Francis et al., 1999). Similar environmental influences on the development of behavioral pathways have been described in rhesus monkeys (Champoux et al., 2002), and studies of premature human infants show substantially greater increases in body weight after introduction of massage therapy (Field, 2002). In contrast, disruption of maternal bonding during infancy has been shown to have profound negative effects on later relationships (National Research Council and Institute of Medicine, 2000). CHILDREN’S BEHAVIOR As used in this report, behavior refers to a child’s emotions, beliefs, cognitions, and attitudes, as well as his or her overt behaviors. Some behaviors are planned and deliberate; others are reflexive, impulsive, and contingent on environmental circumstances. A child’s emotions, beliefs, and attitudes affect health, principally through the way they modify a child’s explicit and overt behaviors, such as his or her health and life-style choices. These in turn alter the child’s eventual health outcomes. Examples include social and interactional behaviors (e.g., compliance with parental requests, peer interactions), health preventive behaviors (e.g., avoiding smoking, driving with a seat belt, choosing good friends), or illness-management-related behaviors (e.g., behavioral adherence with a treatment regimen or health care appointments). Health-related behaviors may be health promoting (those that increase the likelihood of future health, such as regular balanced diet and exercise) or health impairing (those that adversely cause actual morbidity or mortality, such as smoking, drinking, or reckless driving). A body of recent research suggests how these behaviors develop and describes the role of family, peers, and social environment, including media, in shaping this developmental process (Tinsley, 2003). While behaviors like smoking, drinking, and exercise are known to affect later health, it is not clear how these behaviors develop in childhood (McGinnis and Foege, 1999). Often these health behaviors are considered proxies for health, even though they may not necessarily constitute health per se. Some health policies attempt to change youth behaviors that are thought to affect health. An example is the re-

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health quirement for regular school attendance, which may both reflect current health and exert effects on a given child’s likelihood of future health. Behavioral influences on children’s health are often reciprocal, both influencing and influenced by parents, peers, and others. For example, parenting style, family traditions, and peer influences affect not only fairly simple youth behaviors, such as compliance with behavioral requests or participation in health prevention programs (Patterson and Fisher, 2002), but also more complex behaviors, such as participation with disease management regimens. This section focuses on the internal psychological factors that underpin children’s behavior, with implications for subsequent health outcomes. Emotions, Attitudes, and Beliefs In addition to the influence of explicit behaviors on health, a child’s internal emotional, attitude motivation, or belief states may exert effects on health. For example, research on both adults and children has shown direct relationships between internal attitudinal and personality factors and health outcomes, perhaps through mechanisms that link internal emotions, attitudes, and beliefs with stress reactions and immune responses (Berry and Worthington, 2001; Herbert and Cohen, 1993; Kiecolt-Glaser, 1999, Lawler et al., 2000). Thus, external events perceived as stressful by a child may function as triggers for an asthma or inflammatory bowel disease flare, over and above any biological exposure or adherence to therapy (Rietveld and Prins, 1998; Santos et al., 2001). Presumably such effects are conveyed through a child’s emotional arousal states, which in turn result in physiological changes, such as increased pulse and elevated blood pressure, glycemic, and immune responses. This research has solid empirical support in both the adult human and animal research fields (McEwen, 1998; Seeman et al., 1997), but it is less firmly established for children. Behavioral Adaptations The hallmark of childhood is the constant exposure to new developmental challenges. As children acquire new physical and cognitive skills and experiences, their behaviors change. They explore, practice, and experiment and as a result they change and are changed. The resulting behaviors are both manifestations of their health and have significant implications for it. At each new exposure, the child may respond in a variety of ways that in turn unleash a variety of reactions in his or her caregiver and in others around him. From birth, infants recognize, prefer, and are soothed preferentially by their mother’s voice (Mehler et al., 1978; DeCasper and Fifer, 1980). They suckle more in response to it (Mehler et al., 1978), and mothers in turn are gratified by their ability to sooth their children (Klaus et al., 1972). Thus the beginnings of attachment are initiated. As an infant continues his or her explorations and trials, which

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health themselves influence health, they produce reactions from caretakers that in turn further affect the infant’s behavior and health. One of the first developmental challenges faced by an infant is adaptation to extrauterine life. Low-birthweight infants experience more difficult transitions and are more likely to be fussy during social interactions and less likely to smile and vocalize (Beckwith and Rodning, 1992; Barnard and Kelly, 1990). These infant reactions in turn impose stresses on the parent, which may affect the child’s health through impaired attachment. If the parent responds in a fashion that induces further stress in the infant, the increased stress in turn may affect the infant’s ability to secrete adequate amounts of growth hormone (Skuse et al., 1996), potentially leading to growth impairment or failure to thrive. Attempts to make this transition are met with a variety of parental and cultural responses, all of which influence infants in ways that facilitate or impede their development. Nearly a quarter of infants respond to new stimuli in a negative fashion (Kagan et al., 1998); their early infancy imposes a series of challenges that are especially daunting and many are found to still be socially wary and exhibit evidence of physiological stress at age 6 years (Kagan et al., 1987). Emotional development and the establishment of social relationships are among the greatest challenges of infancy and early childhood. Emotions are fundamental for human attachments, social interactions, and self-satisfaction. Therefore, the extent to which infants evoke sympathetic and empathetic emotions in others and eventually develop these emotional expressions themselves greatly influences their subsequent health. Children who do not attain these skills are more likely to encounter rejection from caretakers and peers (Dodge et al., 2003; Schultz et al., 2000). The complex interplay of genetics, parenting, and societal reactions illustrates just how precarious the early years are and how central infant behavior is for subsequent health (Rutter, 1998). Attitudes, Beliefs, and Circumstances The effects of individual, family, and community attitudes and beliefs on health behavior have been well described. A substantial body of research has been conducted on issues related to adherence to treatment regimens, both among parents of younger children and among adolescents (McQuaid et al., 2003; Volovitz et al., 2000; Davis et al., 2001). This work focused initially on asthma and diabetes and more recently on substance use and HIV/AIDS treatment (Manne, 1998). Current research is informed by several related theoretical models of behavior, all of which take into account youths’ attitudes, beliefs, and subjective perceptions about the risks of negative outcomes, as well as the perceived benefits and difficulties of treatment (Hochbaum, 1956; Ajzen, 1991; Rogers, 1983; Bandura, 1994). In accordance with these models, data suggest that both parents’ and youths’ attitudes are moderately predictive of subsequent health care behaviors, whether

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health observational studies reporting little or no relationship between physical activity and television viewing (Robinson and Killen, 1995; Robinson et al., 1993; Durant et al., 1994). A second hypothesis links television viewing, in particular, to increased caloric intake either from eating during viewing or as a result of food advertising on television, which tends to emphasize high-calorie, high-fat foods with poor nutritional content (Story and Faulker, 1990). There is some evidence that amount of television viewing is related to children’s requests for, and parental purchases of, highly advertised foods (Taras et al., 1989) and that television advertising may produce incorrect nutritional beliefs in children (Ross et al., 1981). There is also experimental evidence that there are direct effects of exposure to advertising for high-calorie foods on children’s snack choices and consumption (Gorn and Goldberg, 1982; Ross et al., 1981). Effects of Sexual Messages and Sexual Content. Throughout childhood, adolescence, and young adulthood, people continually learn more about sex, with media being a major source of information (Brown et al., 2002; Dorr and Kunkel, 1990; Wartella et al., 1990). The average child will have viewed over 14,000 sexual simulations and sexual innuendos each year (Derkson and Strasburger, 1994). Experimental studies conducted largely with convenience samples of white, middle-class young adults (often college students) have documented negative effects of nonviolent but dehumanizing pornography, especially on attitudes toward women (Kenrick et al., 1989; McKenzie-Mohr and Zanna, 1990; Weaver et al., 1984). However, the evidence is particularly disturbing in the case of violent pornography. Two major reviews of the literature, one using meta-analytic techniques (Allen et al., 1995a) and the other a conceptual review (Malamuth and Impett, 2001), both conclude that sexual violence has been found to be arousing to sex offenders, force-oriented men, and sometimes even to “normal” young men if the woman is portrayed as being aroused by the assault. Media Use, Cognitive Development, and Academic Skills. Theory and popular perception have proposed that because television viewing involves so little mental effort, it retards cognitive development and the development of such academic skills as reading (Healy, 1990; Winn, 1985). In the case of television, there is a large body of theory and empirical data showing that both the content and form of television programs affect children’s intellectual development and social behavior (Huston and Wright, 1997). Longitudinal studies have found that watching general-audience entertainment programming can have deleterious consequences on both academic and social outcomes (Anderson et al., 2001; Friedrich-Cofer and Huston, 1986; Huesmann and Eron, 1986). But both field experiments and longitudinal studies indicate that watching educational programming in early childhood is positively related to cognitive skills (Ball and Bogatz, 1970; Rice et al., 1990; Zill, 2000), school readiness (Wright et al., 2000),

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health and adolescent academic achievement (Anderson et al., 2001). Much less is known about the effects of video games and computer technologies, but some theorists have proposed that the interactive character of these activities makes them more potent than television as sources of sensorimotor skill, intellectual stimulation, and messages about violence and other social behaviors (Calvert and Tan, 1994; Cocking and Greenfield, 1996; Greenfield, 1994). Researchers have demonstrated academic gains in young children of both genders, using developmentally appropriate software (i.e., software allowing children to control the program and make decisions) in academic settings in such skill areas as verbal ability, problem solving, and creativity (Haugland and Wright, 1997). Cultural Environment Culture is often defined by the ideas, beliefs, and values coupled with the rituals and practices of social groups, including but not limited to families. Betancourt and Lopez suggest that culture refers to “a distinct system of meaning or a cognitive schema that is shared by a group of people or an identifiable segment of the population” (García Coll and Magnuson, 2000, p. 97). Miller and Goodnow define cultural practices as “actions that are repeated, shared with others in a social group, and invested with normative expectations and with meanings or significances that go beyond the immediate goals of the action” (National Research Council and Institute of Medicine, 2000, p. 60). Thus, practices to prevent and promote health and provide treatment have to make sense and be congruent with these systems of meanings and practices. In addition, any self-report on health is embedded in these cultural constructions. In the United States, the relationship of culture to health outcomes and their measurement is particularly significant because of the growth in diverse populations. It is estimated that by 2050, children of color will account for a majority of children in this country (Institute of Medicine, 1997). Consequently, dominant notions of health—mostly based on middle-class, northern European beliefs and practices—are increasingly out of alignment with the traditions, customs, and beliefs of those with other ancestries. Culture affects health in many ways. One is by promoting daily activities and routines that reflect culturally defined goals and values that interact and influence developmental processes, inclusive of health (Gallimore et al., 1993; Rogoff, 1990). These routines can include, for example, health-promoting habits such as culturally prescribed foods and activities that provide adequate nutrition and caloric intake or patterns of mother-infant interaction (e.g., Harwood, 1992). Culture also affects health by providing caregivers (and eventually children themselves) with an understanding of development and health: culture offers the context for defining what is a problem, explaining why the problem exists, providing possible treatments, and indicating who should respond (Groce and Zola,

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health 1993; Harwood et al., 1999). Similarly, culture also provides a framework for the use of home remedies. There are studies on the use of cupping and coining, traditional practices in some cultures that have been confused with child abuse (Moy, 2003; Bullock, 2000; Hansen, 1998). Cupping, a practice used by various cultures including Chinese, Arabic, and Jewish, involves attaching cups on one’s back and creating a vacuum to evacuate a malady and increase blood flow to the region, leaving marks that can be confused with the result of trauma to the area. Similarly, coining is the practice of rubbing the edge of a coin on one’s skin as a treatment for an illness. Other examples of the importance of cultural meaning of health and disease definitions are the “empacho” theory used by Latin Americans (food is claimed to be “stuck” to the intestines causing vomiting, diarrhea, or early satiety—many families seek the help of folk healers or home remedies consisting of such dangerous substances as lead and mercury) and the use of “hot-cold” remedies, which were mentioned in Chapter 1 (Nuñez and Taft, 1985; Risser and Mazur, 1995). In the United States, variables such as language proficiency, acculturation level, and recency of migration have all been identified as important sources of variability within cultures (Gutierrez et al., 1988) with significant impact on health. Biculturalism (identifying simultaneously with two cultures) rather than linear acculturation (adopting a single cultural identification over time) has been found to be related to better outcomes (Gil et al., 1994; Szaponick et al., 1981). An interesting finding in the health literature is what has been termed the “Latino epidemiological paradox” (Markides and Coreil, 1986) or “the immigrant paradox” (Fuligni, 1997; Portes and Rumbaut, 2001), whereby recent immigrants who tend to be more economically deprived and less acculturated, or individuals from Hispanic backgrounds in general, tend to have better health outcomes than other groups from the same ethnic backgrounds or non-Hispanics (Hayes-Bautista et al., 2002; Hayes-Baustista, 2003). The mechanisms behind these surprising findings are not well understood. One possibility is that of selection bias; that is, first-generation immigrants to the United States may be the healthiest and most motivated subset of potential immigrant families. But it has also been hypothesized that traditional cultural practices serve as protective factors. These and other findings have led investigators to posit cultural differences as sources of both risk and resilience (García Coll et al., 1996; García Coll and Magnuson, 2000). In other words, culture does not constitute a source of vulnerability or risk per se, but cultural differences can become a source of risk when (1) cultural differences are seen as deficits that need to be remedied or fixed, (2) cultural differences lead to mismatches between caregivers or the child themselves and members of dominant institutions, and (3) cultural differences lead to experiences of discrimination and diminished life opportunities due to segregation. There is evidence that these sources of stress are not limited to low-income

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health populations but are experienced by groups with higher socioeconomic backgrounds as well (McAdoo, 1981; Tatum, 1987). Discrimination A sparse but growing literature on discrimination, particularly regarding race and ethnicity, documents its effect on health. Krieger (2000) reviewed 20 research articles that used instruments to measure self-reported experiences of discrimination: the most common association with discrimination (10 studies) was with mental health; the second (5 studies) was with hypertension. Unfortunately, all studies concerned adults only. A more recent review confirmed the findings of a substantial association between racial/ethnic discrimination and mental health, with additional associations with various physical health measures (Williams et al., 2003). In one study, simulated racial discrimination was associated with physiological dysfunction, which was associated with subsequent poor health (Harrell et al., 2003); again, the studies included adults only. Van Ryn and Fu (2003) proposed a pathway through which health provider behavior in clinical or public health settings contributes to discrimination. In this case, the pathway would be as relevant to children as to adults, as adults generally accompany children in health services encounters and act as proxy for them. Nazroo (2003), reviewing evidence on ethnic discrimination from the United Kingdom, concluded that social and economic inequalities, underpinned by racism, are a fundamental source of ethnic inequalities in health across population subgroups. Chaturvedi (2001) suggested that recognition of different kinds of effects from racism, including on children, could help to sort out the pathways by which the multifactorial and interacting influences affect various aspects of health. To that effect, a recent review (McKenzie, 2003) provided added evidence for an effect of racism on health, including the documentation of racism as well as the mechanisms by which it operates. SERVICES Although few would debate the relevance of health services to improving individual health, many have actively debated the contribution of health services to the health of populations. In recent decades, writers such as Thomas McKinley have made strong arguments that improvements in population health have come more from improvements in other spheres (particularly nutrition) than from interventions provided by health services (McGinnis et al., 2002). Although there is increasing recognition of the effect of services in the behavioral and social arenas on health (Institute of Medicine, 1997, 2000), evidence regarding specific outcomes of these programs is limited.

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health In contrast, the medical literature is replete with reports of the effectiveness of specific biomedical interventions that influence the course of particular diseases. John Bunker has gone further and estimated that health services in general account for about half of improvements in health (measured as increases in life expectancy) in the most recent half-century (Bunker, 2001). While his monograph demonstrates the important role of health services, it reinforces the simultaneous importance of other influences. The effect of social factors on health, and the possibility of their remediation, does not detract from the importance of health services, at least in part because one of the correlates of social factors is differential access to and appropriate use of health and other services. Documentation of the overall effect of services specifically on children’s health is more limited. A 1985 publication on the importance of health services on the incidence, prevalence, and severity of 16 important conditions in childhood (Starfield, 1985b) illustrated the importance of access to health services. However, this study provided no quantitative estimates of the total magnitude of effect of health services on the child population, and it predated numerous new vaccines and other general environmental improvements that have further reduced morbidity and mortality. It was also based on a model of health that was more disease-oriented than the multifaceted conceptualization of health proposed in this report. In more recent years, it has become clear that the nature of health services, rather than simply their presence, is important. For example, an accumulating number of studies, both in the United States and abroad (as well as international comparative studies) have shown the importance of a strong primary care orientation in health services systems (Starfield et al., 1998). The benefits of a strong primary care orientation are even more salutary for children than for adults (Shi and Starfield, 2002). Comprehensive, high-quality center-based early education has been demonstrated to improve a range of educational outcomes (National Research Council and Institute of Medicine, 2000). A growing literature supports the ability of early intervention services to intervene and modify developmental health trajectories in children who are at risk of developing developmental, behavioral, and mental health conditions (Ramey et al., 1992; Karoly et al., 1998; Olds and Kitzman, 1993; Olds et al., 1997, 1998, 1999). The availability and configuration of services in a given community can be logically assumed not only to affect a range of children’s health outcomes, but also to create a context for and to affect the range of other influences. Figure 3-1 presents a theoretical framework modified from Halfon and Lawrence (2003) to illustrate how services can direct or modify a course of healthy development; modify predisease pathways; and minimize the risk of exposures before they occur, thereby actively promoting the development of health capacities. Services can reduce exposure to health-compromising events. For example, there is strong evidence that multiple doses of pneumococcal vaccine lead to

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health FIGURE 3-1 Where services can effect change in healthy development. SOURCE: Adapted from Halfon and Lawrence (2003). significant decreases in otitis media (ear infections) and subsequent hearing loss (Fireman et al., 2003). Public health activities to improve nutrition and public health education campaigns have resulted in health improvements. For example, introduction of folic acid in grain-based products decreased the risk of neural tube defects (Fletcher and Fairfield, 2002). The Back to Sleep campaign, aimed at educating adults on proper infant sleeping position, has been credited with a dramatic reduction in the occurrence of sudden infant death syndrome (Willinger et al., 1998). Services can modify the relationship between exposure and the onset of disease once the child has been exposed—thereby altering the nature of the exposure outcome pathway. Children exposed to a case of meningitis may receive prophylactic antibiotics to avoid coming down with the disease themselves. Newborn screening identifies infants with phenylketonuria, enabling dietary modification that avoids adverse manifestations of the disorder. Another way in which services influence health outcomes is to modify or reduce a disease or to promote a specific rehabilitation or habilitation process. For example, the lives of children with cystic fibrosis have been transformed and their prognoses improved as a result of service delivery systems that have lengthened life expectancy and improved functional capacity (Schechter, 2003). Services relevant to children’s health include a broad array of interventions, such as health promotion and preventive services, diagnostic, treatment, and rehabilitative services, educational programs, and a variety of social services. They include specific health interventions, such as immunizations, as well as programs of integrated services that systematically address prevention, promotion, treat-

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health TABLE 3-1 Illustrative Services for Children, Youth, and Families Prevention-Oriented Treatment-Oriented Long-Term Care, Home and Community-Based Care Early intervention programs; early literacy Infectious disease control Nutritional services Lactation services Exercise programs Safe sex education Injury prevention programs Topic-specific health education targeted at schools, child care, and parenting Media campaigns Environmental risk abatement programs (e.g., lead) Vision and hearing screenings AIDS education, testing, and counseling Smoking and substance abuse prevention Prenatal care; pre- and postpregnancy counseling Immunizations and well-baby care Developmental, behavioral, and mental health assessment and guidance Genetic screening and counseling High-risk mother and infant care services Emergency medical services Smoking and substance abuse cessation programs Acute medical care Mental health, behavioral treatment, and therapy Chronic disease management Medication management, rehabilitation therapies Crisis intervention High-risk mother and infant care services Emergency medical services Smoking and substance abuse cessation programs Acute medical care Mental health, behavioral treatment, and therapy Chronic disease management Crisis intervention Long-term inpatient mental health care Chemotherapy, cancer radiation treatment Convalescent and rehabilitation care Child protective services Home visiting Home health care Child care School-based clinics Case management care coordination Caregiver respite After-school programs Peer support groups for adolescents Social skills development, stress management School-based special education and rehabilitation for developmental delay, learning disability, mental health problems and programs for gifted and talented students ment, and risk reduction simultaneously, as is the case in model chronic disease management programs (American Academy of Pediatrics, 2002). Services function at several different levels, including the level of the individual child, family, and community, as well as larger social, physical, and policy environments. Table 3-1 lists a range of potential services relevant to children’s health that reflects the committee’s conceptualization of it. While not exhaustive, this list depicts a continuum of services designed to improve the health of children and the functions they serve. It includes services provided by the personal and public health system, as well as the environmental health, education, and social service systems. Prevention-oriented services are shown to include health promotion services that are focused at the population level (e.g., injury prevention, anti-smoking campaigns), as well as services that are part of ambulatory health care provided through the primary care system (e.g., immunizations). Treatment-

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health oriented services include those that are provided in clinical encounters and ambulatory care settings (e.g., acute medical care), as well as those that are provided in hospitals (e.g., emergency services). Long-term, home, and community-based care includes community-based rehabilitative services designed to restore function (e.g., physical therapy), as well as habilitative services designed to maintain the development of function (e.g., speech or language therapy for children with language impairments). Research is warranted to tease out the role that a range of services play in mediating and modifying influences so children can stay healthy, as well as supporting and promoting their optimal health. Improved specification of the effects of services, better targeting and customizing of services for specific populations, and improved monitoring of the effect of specific services on population health measures should be considered important research and analysis priorities. POLICY The health of children in the United States is affected by laws, rules, and regulations developed at the national, state, and local levels. These governmental actions determine the availability of publicly supported services and often regulate the provision of privately administered services. They are integral to how communities operate. Policies directed specifically at health or health care services, such as eligibility for publicly funded insurance (Currie and Gruber, 1996a) or requiring a child to be immunized prior to starting school (Briss et al., 2000), have both intuitive and documented effects on children’s health. But many improvements in children’s health over the past century were also influenced by policies in areas other than health. Prominent examples include improvements in children’s health as a result of the decision to include vitamins in food products (e.g., vitamin D in dairy products and folic acid in cereals and breads) and fluoride in drinking water (Centers for Disease Control and Prevention, 2001); drinking water and food quality standards (Environmental Protection Agency, 1996; Perdue et al., 2003); educational and child care standards and programs (e.g., the Individuals with Disabilities Education Act); and environmental emissions and engineering safety standards (Perdue et al., 2003). Innumerable serious injuries and deaths have been prevented by traffic safety standards, such as car seats and speed limits (Sleet et al., 2003; Farmer et al., 1999), consumer product safety standards (Sleet et al., 2003), and such building codes as requiring fencing around swimming pools and safety protections on high-voltage electrical equipment (Stevenson et al., 2003). The policy environment also affects children’s health in less obvious ways. For example, welfare policy decisions play a role in families’ SES and even child achievement (see discussion below), and education policies play a role in the availability and quality of schools in a given community (Chase-Lansdale et al., 2003).

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health Although many policies affect children’s health, most are developed and implemented without formal consideration of their effect on children. It is beyond the scope of this report to provide a comprehensive review of all policies that have had an impact—or could have an impact—on children’s health. Instead, we illustrate the importance of policy with discussions of fluoridated water, children’s health insurance, and welfare reform. Fluoridated Water Fluoridation of drinking water has contributed to reductions in dental caries in both children and adults (National Research Council, 1993), and the Centers for Disease Control and Prevention (CDC) has highlighted water fluoridation as a significant public health achievement (Centers for Disease Control and Prevention, 1999b). Cross-sectional studies conducted in the mid-1900s showed water fluoridation to have an effect on dental caries and prompted policies to fluoridate water in many cities throughout the United States. A review of studies on the effectiveness of water fluoridation conducted in the United States between 1979 and 1989 found that caries were reduced between 8 and 37 percent among adolescents (Newbrun, 1989). There is some evidence that water fluoridation has been particularly beneficial for communities of low socioeconomic status (National Research Council, 1993; Riley, Lennon, and Ellwood, 1999), perhaps attributable to their disproportionate burden and lower access to dental care. Evidence of the effectiveness of water fluoridation in reducing dental caries has led to other approaches to introduce fluoride, including the addition of fluoride in toothpastes and topical fluoride treatment by dental professionals. There has been some debate about whether water fluoridation increases the risk of a range of other health conditions, including cancer, osteoporosis, and Down syndrome. A review by the National Research Council (NRC) in 1993 concluded that there was no credible evidence to support these claims. The NRC is currently conducting a study to review the evidence since 1993 and advise EPA on the adequacy of its current water fluoride standards in the context of the variety of fluoride sources now available. Health Insurance The role of health insurance for health care access and service use2 has been a focal point of health policy and specifically children’s health policy over several 2   Policies focused on improving the quality of health services available to children in the United States are equally important. Because there is an extensive literature on the importance of appropriate health care treatments to improve health in the face of disease, we do not review that here, but underscore the importance of access to care based on the information that health can be enhanced through health care.

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health decades. In contrast to all other industrialized nations and despite frequent incremental attempts to expand health insurance coverage, a substantial proportion of children remain uninsured, and many more have inconsistent or inadequate health insurance (http://www.census.gov/prod/2003pubs/p60-224.pdf). While health insurance is an important contributor to access to and use of health services (Starfield, 2000a; Currie and Gruber, 1996a), it is far from the only factor. The availability and distribution of providers, the functioning of the primary care system, and multiple nonfinancial barriers are also important variables that affect health care access and use (Starfield et al., 1998; Halfon, Inkelas, and Wood, 1995). The two primary publicly funded programs that provide health insurance for children—Medicaid and the State Child Health Insurance Program (SCHIP)—require families to demonstrate initial and continuing financial eligibility. Implemented in the 1960s, Medicaid coverage increased dramatically during the 1980s and early 1990s as a result of major policy changes in laws that sought to expand Medicaid eligibility (Currie and Gruber, 1996a). Although participation in Medicaid programs is far from universal (Cutler and Gruber, 1996), and most uninsured children still receive medical care, the increased access to health care afforded by Medicaid has been associated with better birth outcomes (Currie and Gruber, 1996b), lower rates of preventable illness (Starfield, 1985a) and improved efficiency of medical care delivery (Dafny and Gruber, in press). In 1997, SCHIP was initiated to provide further health insurance coverage for uninsured children. SCHIP provided additional funds to states to expand their health insurance coverage by either using Medicaid expansion or, alternatively, developing state-run health insurance programs for children. Despite these efforts to expand insurance coverage, far-from-universal SCHIP program take-up and other factors still left 9.2 million children without health insurance coverage in 2001 for the full year (http://www.census.gov/prod/2003pubs/p60-224.pdf; LoSasso and Buchmueller, 2002). An additional number lack insurance for part of the year. States with policies that facilitate eligibility and certification procedures have been shown to have higher rates of enrollment (Dick et al., 2003). Health insurance of any type cannot facilitate access to health care services when the necessary resources are not present. In the absence of national health insurance, national health policy has supported the development of a safety net of services in the form of community health centers in areas with a shortage of health facilities and personnel. Currently there are about 800 such centers across the country, all of which provide high-quality primary care services. Recent evaluations indicate that the presence of these centers improves the health of children and reduces racial disparities among the populations who receive services from them (Politzer et al., 2001; Shi and Starfield, 2000).

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Children’s Health, The Nation’s Wealth: Assessing and Improving Child Health Welfare Policy From a policy perspective, it is important to ascertain to what extent policies directed at families or adult family members, even if not explicitly targeted on child well-being, in fact alter children’s chances of healthy development. We illustrate this kind of policy analysis with the welfare reform law (the Personal Responsibility and Work Opportunity Reconciliation Act of 1996), which was directed first and foremost at increasing the employment and reducing the welfare dependence of mothers. Evidence on the likely effects of welfare reforms comes both from random-assignment experiments and from longitudinal survey studies (National Research Council and Institute of Medicine, 2003). A key finding from the experiments is that effects on the achievement and behavior of younger children were consistently more positive in programs that provided financial and in-kind supports (earnings supplements) for work than in those that did not. The packages of work supports were quite diverse, ranging from generous earnings supplements provided alone to more comprehensive packages of earnings supplements, child care assistance, health insurance, and even temporary community service jobs. At the same time, these experiments produced evidence of negative effects on adolescent achievement across all types of programs, although a prominent nonexperimental study did not replicate the negative adolescent results (Chase-Lansdale et al., 2003). Systematic approaches to evaluate the effect of policies on children of this sort are the exception, rather than the rule, and few other systematic attempts can be identified. CONCLUSION This chapter provides a discussion of evidence concerning the influence of various types of characteristics on the health of children. Although imperfectly understood, the important role of interactions of these influences, which may differ in kind and amount at different ages and stages of development, is amply supported by the evidence. Notably absent from most of the discussion, however, is the relative importance of the various types of influences on children’s health at different ages. For the most part, evidence for the influences comes from studies of the relative risk imposed by them. However, exposure to influences differs in frequency from one influence to another. Influences that have a high relative risk may be of only minor importance to the health of the population of children if they are relatively uncommon. In order to understand the effect of these factors on the health of children, such information is critical (see Goodman et al., 2003).