Childhood Precursors of Adult Morbidity and Mortality in Developing Countries: Implications for Health Programs

W.Henry Mosley and Ronald Gray

INTRODUCTION

The developing countries of the world are in the midst of a demographic and epidemiologic transition that is profoundly transforming their health profile (Mosley and Cowley, 1991). Prior to World War II, most developing countries experienced high rates of mortality, with infectious diseases of childhood dominating the epidemiologic picture. In the postwar period, largely as a result of advancements in medical technology directed against infectious and parasitic diseases, there have been rapid declines in infant and child mortality that, coupled with the high levels of fertility, have produced rapidly growing populations with a very young age structure. Beginning in the 1960s and accelerating through the 1970s and 1980s, birth rates declined in much of the developing world, initiating a process of slower population growth. This reduction in the growth rates, however, initially occurs among infants and children; the population of adults will continue to grow for decades into the future because of the large numbers of children already born who will survive to reach the older age groups (Chenais, 1990).

There were dramatic changes in the age structure of the world’s population between 1960 and 1990 that will continue into the first quarter of the next century, according to estimates and projections by the United Nations

W.Henry Mosley and Ronald Gray are at the Department of Population Dynamics, the Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland. The authors acknowledge the assistance of Dr. Aida Abashawl and Dr. Laura F.Robin in the preparation of this paper. Partial support for the work was provided by the U.S. Agency for International Development under Child Survival Cooperative Agreement DPE-5951-A-00–5051.



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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings Childhood Precursors of Adult Morbidity and Mortality in Developing Countries: Implications for Health Programs W.Henry Mosley and Ronald Gray INTRODUCTION The developing countries of the world are in the midst of a demographic and epidemiologic transition that is profoundly transforming their health profile (Mosley and Cowley, 1991). Prior to World War II, most developing countries experienced high rates of mortality, with infectious diseases of childhood dominating the epidemiologic picture. In the postwar period, largely as a result of advancements in medical technology directed against infectious and parasitic diseases, there have been rapid declines in infant and child mortality that, coupled with the high levels of fertility, have produced rapidly growing populations with a very young age structure. Beginning in the 1960s and accelerating through the 1970s and 1980s, birth rates declined in much of the developing world, initiating a process of slower population growth. This reduction in the growth rates, however, initially occurs among infants and children; the population of adults will continue to grow for decades into the future because of the large numbers of children already born who will survive to reach the older age groups (Chenais, 1990). There were dramatic changes in the age structure of the world’s population between 1960 and 1990 that will continue into the first quarter of the next century, according to estimates and projections by the United Nations W.Henry Mosley and Ronald Gray are at the Department of Population Dynamics, the Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland. The authors acknowledge the assistance of Dr. Aida Abashawl and Dr. Laura F.Robin in the preparation of this paper. Partial support for the work was provided by the U.S. Agency for International Development under Child Survival Cooperative Agreement DPE-5951-A-00–5051.

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings (1991). For example, in developing countries in particular, the population under age 15 will have only slightly more than doubled over this 60-year time span, but the population age 15 to 64 will have increased by almost four times to 4,441 million in 2020, and the population over age 65 will have increased almost six times to 472 million in 2020. This rapid aging of the population will have a profound effect on the health system, which will have to shift its priorities toward the prevention and management of chronic diseases among adults (Mosley et al., 1993). This paper examines only one aspect of the health transition in developing countries. It looks at the emerging health problems among the adults and the aged, and assesses to what degree these chronic diseases and disabilities might be a consequence of infectious diseases and other adverse conditions that were experienced decades earlier in infancy and childhood. A recognition of these relationships can enhance our understanding of the cost-effectiveness and cost-benefits of programs to promote child health. Child health interventions are not only cost-effective in saving lives and preventing disabilities in the short run but, more importantly, in the long run can result in major cost savings to health systems and can accelerate national development by improving the health and productivity of these children when they become adults. BACKGROUND Recently, Elo and Preston (1992) completed a review of the literature examining the effects of early life conditions on adult mortality. Their review begins with a discussion of the epidemiologic evidence for some of the major mechanisms whereby exposures and morbidity in childhood may have health consequences for adults. Initially, they examine a number of specific infectious diseases of childhood with well-documented, long-term health effects among adults (tuberculosis, hepatitis B, rheumatic heart disease) and then look at the growing literature suggesting that a number of chronic cardiovascular and pulmonary diseases may be related to a range of risk factors beginning in the intrauterine environment (e.g., intrauterine growth retardation) and extending through disease exposures and behavior patterns acquired in childhood (e.g., acute respiratory infections, dietary consumption of fat and salt). They examine other associations including a number of studies postulating that viral infections acquired in childhood may be linked to a wide variety of chronic diseases ranging from cancer to multiple sclerosis, juvenile diabetes, rheumatoid arthritis, and presenile dementia, as well as the extensive literature linking short stature and adult mortality. Elo and Preston’s review then turns to population-based studies among cohorts of adults that seek to link conditions around birth and early childhood to differentials and subsequent mortality. They find that a wide variety of

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings studies based on data from nineteenth and twentieth century Europe with findings that are generally consistent with the hypothesis that the childhood environment plays a substantial role in adult mortality. The analysis in this paper extends the work of Elo and Preston (1992) in several ways. First, it takes a more epidemiological approach, looking at a broader range of disease conditions in infancy and childhood where the evidence supports a direct relationship to adult morbidity and mortality. Second, our analysis is oriented to the current situation in developing countries with the objective of trying to assess the probable magnitude of the health effects of selected childhood diseases on adult morbidity and mortality. Our assessment admittedly is more speculative, given the data limitations in most developing countries. Our purpose will be achieved, however, if this analysis highlights the need for more research on these issues as well as the importance of maintaining and expanding programs to promote child health in the developing world. CLASSIFICATION OF DISEASES OR CONDITIONS OF INFANCY AND CHILDHOOD WITH CONSEQUENCES FOR ADULTS There are a wide range of health conditions affecting infants and children in developing countries that have long-term consequences for adult health. Table 1 classifies these conditions into four groups: (1) conditions acquired in the perinatal period; (2) infectious diseases of childhood; (3) nutritional deficiencies of infancy and childhood; and (4) environmental hazards. This classification system is by no means comprehensive, but it does include many of the major diseases and conditions that have substantial effects on adult health and survival. The first part of this paper briefly discusses each of these conditions, focusing particularly on the available information relating childhood diseases to adult health consequences. Where data are available, the magnitude of the problem in terms of effect on adult health is provided. In the concluding section of this paper we take a more integrated approach by examining some of the interactions among childhood risk factors in producing adult diseases. Also, recent trends in adult cause-of-death data from selected developing countries are examined to assess how mortality profiles may be related to conditions acquired in childhood several decades earlier. Perinatal Conditions Low Birthweight Twenty million newborns per year, or 16 percent of all children born worldwide, are considered to be low birthweight as defined by a weight of

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings TABLE 1 Consequences of Selected Infant and Childhood Health Problems for Morbidity and Mortality in Adults Conditions in Children Consequences in Adults Perinatal conditions   Low birthweight Growth stunting, chronic obstructive pulmonary disease Birth trauma, asphyxia, metabolic disorders Brain damage, cerebral palsy, mental retardation Congenital and perinatal infections   Hepatitis B Liver cancer, chronic liver diseases Syphilis Blindness, deafness, paralysis, bone disease Gonorrhea Blindness Infectious diseases of childhood   Tuberculosis Tuberculosis Rheumatic fever Chronic rheumatic heart disease Poliomyelitis Residual paralysis Trachoma Blindness Chagas’ disease Heart failure Schistosomiasis Liver cirrhosis, general debility Helicobacter pylori Stomach cancer Epstein-Barr virus Nasopharyngeal cancer, Burkitt’s lymphoma Nutritional deficiencies in infancy and childhood   Protein-energy malnutrition Growth stunting, obstetrical complications, cardiovascular disease, chronic pulmonary diseases, intellectual impairment Micronutrient deficiency   Iodine Cretinism, intellectual impairment Iron Learning disabilities, intellectual impairment Vitamin A Blindness Environmental hazards   Indoor air pollution Chronic obstructive pulmonary disease, lung cancer Lead exposure Intellectual impairment less than 2,500 grams (World Health Organization, 1990). Ninety percent of low-birthweight infants are born to mothers in developing countries. More than two-thirds of these occur in the countries of South Asia where approximately one birth in four is low birthweight. The overall risk of delivering a low-birthweight infant in a developing country is three times that in an industrialized country. In South Asia the risk is four times greater. In developing countries, approximately 80 percent of low-birthweight

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings infants are a result of intrauterine growth retardation (IUGR) rather than prematurity (Villar and Belizan, 1982). IUGR is primarily a consequence of inadequate energy and protein intake during pregnancy, often coupled with excessive energy expenditure during the later stages of pregnancy because of the heavy work load of most poor women in the developing world (Kramer, 1987). Adolescent pregnancy and maternal stunting are associated with low birthweight (Herrera, 1985). Additional factors are traditional practices of dietary restrictions during pregnancy, maternal infections such as malaria, and possibly close spacing of births (Kramer, 1987). Cigarette smoking and smoke from biomass cooking fuels may also be implicated (Ferraz et al., 1990; Mavalankar et al., 1993). Studies in Guatemala, Colombia, India, Mexico, the United States, and Canada have confirmed that supplemental nutrition can increase birthweight (Pinstrup-Anderson et al., 1993). Improvement in birthweight appears to be greatest if supplementation is provided in the third trimester of pregnancy. It is noteworthy that most low-birthweight newborns in societies experiencing high levels of chronic malnutrition are found to remain stunted at below the tenth percentile for height and weight at 3 years of age (Mata, 1978). Elo and Preston (1992) review the evidence indicating that stunted growth is associated with higher risks of mortality among adults, particularly from cardiovascular disease and chronic obstructive pulmonary disease (COPD). The former relationship is examined below in the discussion of protein energy malnutrition. Here we look at the evidence specifically relating low birthweight to respiratory infection in childhood and COPD in adults. Low-birthweight infants have a higher incidence of lower respiratory tract infections than infants with normal birthweight (McCall and Acheson, 1968). As a consequence, low birthweight has been shown to be associated with a higher prevalence of cough and poor lung function in later childhood (Chan et al., 1989). Recently, Barker and colleagues (1991) completed a study relating birthweight and childhood respiratory infections to risk of death from chronic obstructive pulmonary disease and to pulmonary function among men ages 59–67 years in England. They confirmed that low birthweight and severe respiratory infections in infancy were associated with higher risks of death from COPD as well as with compromised lung function among the survivors. They note that an association between low birthweight and obstructive lung disease is biologically plausible, because fetal lung growth, particularly growth of the airways, is largely completed in utero (Bucher and Reid, 1961). Barker et al. (1991:674) conclude from their study that “prevention of chronic obstructive airway disease may partly depend on promotion of fetal and infant lung growth and reduction in the incidence of lower respiratory tract infection in infancy.” COPD is a leading cause of death among adults in developing countries, and the high incidence of low birthweight in these settings is undoubt-

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings edly a contributing factor. Because there are other important contributing factors in developing countries (see below), COPD is discussed in more detail in the second section of this paper. Birth Trauma, Asphyxia, Metabolic Disorders In developing countries only about 50 percent of the births are attended by trained personnel (World Health Organization, 1990). One consequence is a perinatal mortality rate four to six times higher than that seen in developed countries, where more than 99 percent of births take place in the presence of a trained attendant, and typically in a hospital setting. Unfortunately, data are lacking on the incidence of birth injury, asphyxia, and preventable metabolic disorders (such as hyperbilirubinemia secondary to physiologic jaundice) that can produce permanent disabilities among surviving infants in developing country settings. Brain damage leading to mental retardation, cerebral palsy, and other neurological disabilities would be among the most serious consequences with a lifelong influence on health status. Although incidence data are not available, there are some clinical studies suggesting that birth injury is a significant contributor to chronic neurological disease. Nottidge and Okogbo (1991) found that among 413 children presenting with cerebral palsy in Ibadan, Nigeria, 41 percent appeared to be related to bilirubin encephalopathy and 20 percent to birth asphyxia. The patients seen in this urban referral center are by no means representative of the population; however, the data do suggest that a high proportion of brain damage seen in infants may be attributable to conditions preventable in the perinatal period. It is not clear how these observations may relate to neurological disability seen among adults, but the data are at least consistent with the thesis that inadequate antenatal and childbirth care can contribute significantly to the level of chronic disability in a population. This thesis requires far more research. Congenital and Perinatal Infections There are a number of maternal infections that may be transmitted to the fetus in utero or to the newborn around the time of childbirth that have significant consequences for adult health. Hepatitis B By far the most prevalent and serious disease in this category is related to the maternal-infant transmission of hepatitis B virus (HBV) (Francis, 1986; Kane et al., 1993). The World Health Organization (1990) estimates that more than two billion individuals have been infected with HBV, of whom 280 million are chronically infected carriers of the virus. Prospective population-based studies indicate that ultimately, ap-

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings proximately one-quarter of these chronically infected individuals will die from chronic active hepatitis, cirrhosis, or primary liver cancer. HBV infection is directly related to one to two million deaths per year (World Health Organization, 1990). The prevalence of chronic HBV infection ranges from 6 to 10 percent throughout much of East and Southeast Asia and sub-Saharan Africa. For the rest of Asia, HBV prevalence is 3 to 5 percent, and it is 1 to 2 percent in Latin America (Francis, 1986). Mother-infant transmission in the perinatal period is the primary reason for the high carrier rates in areas where hepatitis B is prevalent. Figure 1 from Beasley (1982) provides a schematic representation of the cycle of HBV infections and liver cancer from generation to generation. If the mother is an HBV carrier, approximately 50 percent of newborns will be infected, 95 percent of whom will become carriers. The daughters will grow up to transmit the virus to the next generation. Ultimately, about half the sons and 14 percent of the daughters will die of chronic liver disease and liver cancer later in life. FIGURE 1 Schematic representation of the intergenerational cycle of hepatitis B infection, chronic liver disease, and liver cancer. SOURCE: Beasley (1982:22S). Permission to reprint granted. From “Hepatitis B virus as the etiologic agent in hepatocellular carcinoma: epidemiologic considerations”. Hepatology 2(2):21S-26S.

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings FIGURE 2 Liver cancer: Age-specific mortality rates per 100,000 population. SOURCE: Barnum and Greenberg (1993). Demographically, HBV is an important cause of mortality among adults in developing countries. Primary liver cancer is a leading cause of cancer death in males in most of sub-Saharan Africa and much of East and Southeast Asia and the Pacific Basin. Figure 2 (from Barnum and Greenberg, 1993) compares the age-specific liver cancer mortality rates from China, where HBV is prevalent, to those from the United States, where maternal-infant HBV transmission is rare, to illustrate the relative importance of this condition in developing country settings. A two-year prospective study of 22,707 Chinese men in Taiwan documented that primary hepatocellular carcinoma and liver cirrhosis associated with HBV accounted for approximately 20 percent of all deaths (Beasley et al., 1981). Consistent with this, Elo and Preston (1992) review a number of demographic studies in East Asia and suggest that the Far Eastern pattern of mortality, characterized by very high death rates at older ages (30+) relative to younger ages, and present primarily among males, may relate to excess mortality as a consequence of a high prevalence of chronic carriers of HBV. Hepatitis B vaccine is now available, and studies have documented that it is highly effective in preventing maternal-newborn transmission of HBV

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings when administered to newborns (Francis, 1986). With recombinant genetic techniques, the cost of production of this vaccine has dropped to approximately $1 per dose, making this a highly cost-effective health intervention in most developing country settings. Syphilis Syphilis and gonorrhea are two other infections transmitted from mothers to infants that can have consequences for adult health. Both of these problems are most serious in sub-Saharan Africa (Over and Piot, 1993). The prevalence of syphilis seroreactivity among pregnant women attending antenatal clinics has been found to range from 4 to 15 percent in a number of regions in eastern and central Africa (Schulz et al., 1987). Based on prospective studies in a variety of settings, from 50 to 80 percent of the pregnancies in these infected women will have an adverse outcome caused by syphilis. In the large majority of cases, congenital syphilis will result in spontaneous abortion or perinatal deaths; however, in 10 to 20 percent of cases, there will be a surviving infant with latent congenital syphilis who may develop active manifestations later in life (Hira et al., 1990). These may include blindness, deafness, paralysis, and a variety of bone lesions. Therefore, in some African populations where about 10 percent of childbearing women are infected, approximately 1 percent of newborns may have congenital syphilis that, if untreated, will result in disabling disease and premature death in adulthood (Schulz et al., 1987). Gonorrhea Maternal newborn transmission of gonorrhea can lead to gonococcal ophthalmia neonatorum (GON) which, if untreated, often leads to blindness. Although prophylaxis or treatment of the eyes with antibiotics is simple and highly effective, it is not available in most poor areas of the world where the vast majority of births occur at home. The World Health Organization (1990) gives a minimal estimate of the annual incidence of gonorrhea at 25 million cases. Again, as with syphilis, a high proportion of these will be in sub-Saharan Africa where diagnosis and treatment are not generally available. The prevalence of Neisseria gonorrhoeae in pregnant women has been reported as ranging between 3 and 22 percent in a dozen countries in sub-Saharan Africa (Schulz et al., 1987). These reported studies were undertaken in urban settings, and some researchers believe that gonorrhea is more prevalent in towns than in rural settings. Because about one-third of the infants exposed to N. gonorrhoeae during birth will develop GON if prophylaxis is not given, one can estimate that the incidence of GON in neonates in Africa may range from 0.5 percent to 6 percent (Schulz et al., 1987). Given that sub-Saharan Africa has more than 20 million births annually, this percentage represents a very large number of children who are exposed to the risk of blindness. Unfortunately, there are no data on the incidence of blindness related to GON in developing countries.

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings Infectious Diseases of Childhood Tuberculosis Tuberculosis represents the classical example of an infection acquired in childhood that manifests itself predominantly with disease among adults. The epidemiological features of tuberculosis were elucidated by Frost in the 1930s (Frost, 1939). Tuberculin skin test surveys in developing countries generally reveal a rather consistent increase in the proportion testing positive for infection with each year of age up to about age 20. The general picture, as represented by a cohort studied in the Netherlands, is that in populations where tuberculosis is endemic, approximately 40 percent of the infections will occur before the age of 5, 67 percent before age 10, and 90 percent by age 19 (Sutherland, 1976). The clinical symptoms of tuberculosis however, are not common with the onset of the infection; rather, after a latent period of some years, approximately 6 to 10 percent of infected individuals will go on to develop active tuberculosis. Eighty-five percent of these cases will be among adults in the most productive age group 15–59 years, as is shown in Figure 3 for several African populations. About 45 percent of the cases will be sputum positive, continuing the cycle of disease transmission to the next generation of children. The economic consequences FIGURE 3 Age distribution of smear-positive tuberculosis in four sub-Saharan tuberculosis programs. SOURCE: Murray et al. (1993: Fig. 2).

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings of this disease are enormous when one considers the estimates that tuberculosis accounts for 18.5 percent of all deaths in the 15–59 age group or 26 percent of all avoidable adult deaths (Murray and Feachem, 1990). Tuberculosis is the single most serious infectious disease in the developing world (Murray et al., 1993). Annual infection rates are highest in sub-Saharan Africa and Asia, ranging from 1 to 2.5 percent; in South and Central America, North Africa, and Western Asia the range is 0.5 to 1.5 percent. Murray et al. have estimated for the developing world in 1990 an annual incidence of 7.3 million cases and 2.7 million deaths. With the diagnostic technology and chemotherapeutic agents currently available, demonstration projects in a number of developing countries have shown that short-course chemotherapy can be applied on a national scale with cure rates approaching 90 percent (Styblo, 1989). Treatment of smear-positive tuberculosis will rapidly accelerate the decline in disease incidence. Analysis of health intervention programs has shown that tuberculosis case therapy is one of the most cost-effective health interventions available (Jamison, 1993). Rheumatic Fever Rheumatic fever is a systemic complication of pharyngitis due to group A streptococcal infection, which can result in inflammatory manifestations principally in the joints and the heart. Infection in children is associated with low socioeconomic status and crowding, and continues to be prevalent in developing countries. Although significant mortality accompanies the acute disease, the chronic consequences of rheumatic heart disease—resulting in disability and ultimately death among young adults in the economically productive ages—represent a significant cost to society. A recent World Health Organization (1988) report notes that “…among the majority of the world’s population, rheumatic heart disease remains the most common cardiovascular cause of death in the first four decades of life.” Rheumatic heart disease remains a significant problem in the developing world (Michaud et al., 1993). Prevalence rates per 1,000 among school-age children included in surveys in different regions and countries of the world were North Africa, 9.9 to 15.0; Nigeria, 0.3 to 3.0; Latin America, 1.0 to 17.0; Asia, 0.4 to 21.0; Pacific, 4.7 to 18.6. Hospital studies in nine sub-Saharan African countries revealed that rheumatic heart disease accounted for 10 to 35 percent of all cardiac admissions (Hutt, 1991). The complications of group A streptococcal pharyngitis (GASP) can be prevented by early diagnosis and treatment with antibiotics. Community-based approaches to promote early detection of pharyngitis, coupled with selection of cases for antibiotic therapy based on the use of a clinical algorithm, have been proposed; at present, however, these are not cost-effective

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings FIGURE 5 Chronic obstructive pulmonary disease: Age-specific mortality rates, China and the United States.

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings mented a direct correlation between declining ambient lead concentrations and blood lead levels in the U.S. population (Shy, 1990). It is important to recognize how exposure to lead occurs in the population. Although combustion of leaded gasoline initially disperses lead into the atmosphere, actually inhalation of lead from the air contributes only 1 to 2 percent of the total lead intake of humans. More important is indirect exposure to atmospheric lead via ingestion and inhalation of lead in dust, soil, food, and water affected by the fallout of atmospheric lead. One study in Italy confirmed that an estimated 60 percent of blood lead levels in the city of Turin was attributable to inhalation or ingestion of leaded fuel emission in dust, food, and water (Facchetti and Geiss, 1982). Not surprisingly, lead exposure is highest among children in urban areas where there is a high density of air, soil, and dust lead levels. A number of epidemiological studies have documented that the developmental effects of chronic low-level lead exposure in early life include low birthweight, impaired mental development in the first two years of life, I.Q. deficits in school-age children, and disturbances in sensory pathways within the central nervous system persisting for five or more years (Shy, 1990). These effects, particularly the neurological and cognitive ones, occur at very low blood lead levels. For example, studies in the United States and Australia in the early 1980s documented evidence of measurable declines in cognitive functions among infants at blood lead levels that were lower on the average than those detected in U.S. school children based on measurements taken in the National Health and Nutrition Examination Survey II (Bellinger et al., 1987; McMichael et al., 1988). The data from these and other studies lead Shy (1990:174) to conclude that “with respect to lead, there should be as little human exposure as possible, and all evidence points to a greater risk of a variety of adverse effects, particularly on cognition and hematological function at what were formerly considered normal blood lead levels.” The adverse effects of lead on human health is well documented in developed countries. Unquestionably the cognitive and neurological deficiencies detectable in children will have consequences for their intellectual development in school and their mental abilities as adults. There are essentially no data on the risks to lead exposure in developing countries; however, the rapid urbanization and increase in the use of motor vehicles indicate that it will be a growing problem in the future. In this context it is noteworthy that in the United States, lead-free gasoline was introduced in the 1970s to protect catalytic converters rather than to prevent disease in human beings. Catalytic converters have not been mandated in most developing countries because of cost considerations; therefore, the use of leaded fuel is the norm. Consequently, one can predict that there will be a growing problem with lead exposure in these settings.

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings SYNERGISM OF CHILDHOOD RISK FACTORS PRODUCING ADULT DISEASE The preceding discussion examines a series of infections and other conditions in childhood in isolation from each other, focusing on their established or possible biological links to morbidity and mortality among adults. This approach, however, oversimplifies the situation because typically there are common underlying risk factors for many of these conditions that are associated with the impoverished living conditions in developing country settings. Chronic obstructive pulmonary disease is used as an example to illustrate how multiple risk factors in childhood can be operating simultaneously and even synergistically to produce disability and death among adults (Samet et al., 1983). Figure 6 illustrates schematically some of the possible underlying childhood determinants of COPD in developing country settings. The use of low-grade, biomass fuels for cooking results in heavy indoor air pollution, which has been well established as a direct contributor to a high rate of acute respiratory infections among infants and children. Indirectly, indoor air pollution may contribute to low birthweight if there is poor ventilation so that women in pregnancy are exposed to significant concentrations of carbon monoxide (Mavalankar et al., 1993). More importantly, under impoverished circumstances the mothers may already be stunted, and this condition, along with poor diets and heavy exertion during pregnancy, can result in low-birthweight infants. Low birthweight, as noted earlier, is associated with impaired lung development, which also increases the risk of acute respiratory infection. In the long run, all of these conditions in combination become precursors of chronic airway obstruction leading to COPD. A similar scenario may be sketched for infant malnutrition, which can result in growth faltering in childhood to produce the long-term health consequences of stunting among adults noted earlier. As with COPD, there are social and environmental determinants of growth faltering and stunting, including poor hygiene and sanitation leading to a high incidence of diarrheal disease. A key point about these theoretical examples is that curative interventions limited to the treatment of acute respiratory infections and episodes of diarrhea can be lifesaving in the short run but may not produce major reductions in adult morbidity and mortality in the long run unless the underlying risk factors are addressed. In the cases cited above, improvements in stove construction, household ventilation, and water and sanitation programs might be expected to produce both short-term and long-term health gains in the population. Relevant in this context is an analysis by Preston and van de Walle (1978) of the gains in survival in a number of French cities in the last century following improvements in the water supply. Data were avail-

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings FIGURE 6 Underlying childhood determinants of chronic obstructive pulmonary disease. able to document that over several decades after sanitary improvements were instituted, gains in survival were initially observed in infants and children and then successively in older groups as the young cohorts aged over time. INFLUENCE OF CHILDHOOD-ACQUIRED DISEASES ON ADULT MORTALITY—COUNTRY STUDIES The data presented above on individual diseases and conditions provide a general assessment of the morbidity and mortality consequences of these conditions for adult health. Although the numbers of persons affected on a global scale are in the tens of millions, it is difficult to assess from such data the relative importance of these childhood conditions compared to other diseases acquired later in life that contribute to adult morbidity and mortality. One problem with making such assessments is the fact that very few developing countries have adequate data at the national level on cause of death. India does have a national sample registration system for vital events that in recent years has included cause of death. These data have limitations because cause of death is based on lay reporting. Indian data do reveal that among adults ages 15–54, tuberculosis alone accounted for 18 percent of deaths among males and 11 percent of deaths among females, indicating that this disease is not inconsequential in contributing to premature mortality (Feachem et al., 1992). Much better data are available from China, which has a national sample

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings registration system providing cause-of-death information, most of it is medically certified, for more than 100 million people. Table 3 from Feachem et al. (1992) summarizes the leading causes of death for Chinese men and women between the ages of 15 and 60 in the year 1988. Noteworthy, cancers of the liver and stomach, due primarily to infections acquired in infancy, account for 13 percent of deaths in men and 9 percent in women. COPD accounts for 11 percent in both men and women. Tuberculosis and rheumatic heart TABLE 3 Distribution of Deaths by Cause for Chinese Women and Men Ages 15–59, 1988 Causes of Death Women (%) Men (%) Communicable 7.1 7.8 Tuberculosis 3.5a 3.8a Maternal 1.8   Cancer 23.6 27.3 Liver 4.3a 8.3a Stomach 4.8a 5.0 Lung 3.8 3.9 Esophagus 2.5 2.9 Colon-rectum 1.4 1.4 Nasopharynx 0.3a 0.9 Breast 1.7   Cervix 0.8   Cardiovascular 23.8 20.4 Cerebrovascular 11.2 10.8 Ischemic 4.3 3.6 Rheumatic 4.3a 2.2a Hypertensive 2.0 2.3 Respiratory 9.9 10.4 Chronic obstructive pulmonary diseaseb 9.5a 9.3a Digestive 5.6 7.5 Chronic liver disease 2.6a 4.2a Endocrine 0.8 0.8 Diabetes 0.6 0.8 Other noncommunicable diseases 6.5 5.7 Injuries 20.9 20.1 All causes 100.0 100.0 Probability of dying (percent) between ages 15 and 59 11.87 14.29 aThese causes are largely related to childhood condition. bPulmonary heart disease is included with chronic obstructive pulmonary disease. SOURCE: Derived from Feachem et al. (1992: Table 2.14).

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings disease together account for 6 to 7 percent of deaths, whereas chronic liver disease, much of which is related to hepatitis B virus, accounts for another 3 to 4 percent. Overall, conditions that are largely related to childhood precursors accounted for more than 30 to 34 percent of all of the premature and generally preventable deaths in this age group. CONCLUSION Typically, when one considers health conditions in developing countries, the focus of attention is on the high levels of infant and child mortality. This focus is reasonable because children under 5 years of age generally account for 15 to 20 percent of the population and the vast majority of deaths in this age group are preventable. What is less appreciated is that the surviving adults in these populations also experience very high rates of preventable morbidity and premature mortality. For example, although we may expect to see 6 to 10 percent of adults dying between the ages of 15 and 60 in developed countries, in developing countries upwards of 25 to 35 percent of adults may die in this period of life. As this review suggests, as many as one-third of these premature deaths may be the consequence of infections and other conditions acquired in infancy and childhood. Although not discussed here, it should be clear that because most of these fatal conditions produce death only after a prolonged chronic illness, the burden of morbidity in the population is far greater. Added to this burden must be that lifetime disability from nonfatal conditions of childhood that produce blindness, paralysis, and mental retardation. The recent child survival revolution in the developing world promoted by UNICEF, WHO, and the international donor community, has brought to the forefront of the world’s attention the cost-effectiveness of a number of selected technical interventions such as immunization and oral rehydration therapy in saving the lives of infants and children. More recently, additional interventions such as antibiotic therapy for acute respiratory diseases have been added to the child survival strategy. For the most part, the goal of child survival programs has been to produce an immediate mortality reduction, and the accomplishments have been noteworthy in many countries (Grant, 1990). A recent exception to this short-term strategy has been the introduction of hepatitis B vaccine into childhood immunization programs in a number of countries in Africa and Asia, including China. The premise of this review is that far more attention should be given to the long-term as well as short-term benefits of programs to promote child health. Attention should be given not only for direct child health interventions such as vaccines but particularly for interventions that will have cross-cutting effects on reducing the risks of multiple conditions simultaneously. Interventions such as reducing indoor air pollution, upgrading housing and

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The Epidemiological Transition: Policy and Planning Implications for Developing Countries - Workshop Proceedings sanitation, and improving pregnancy care and nutrient intake would fit in this category. Too often, when only narrowly defined, short-term benefits are taken into account, such broad-based intervention programs are considered too costly. However, as shown by Briscoe (1978) in terms of improving the water supply, when the multifaceted and long-term health benefits are considered, intervention programs in these areas become quite cost-effective. A major limitation of this analysis is the paucity of empirical data from population-based studies, particularly from developing countries, which could provide a firm basis for establishing the links between childhood exposures and adult morbidity and mortality. More precise knowledge of these linkages would be important for policy and programmatic purposes as well as having scientific significance. Although we can generally expect health conditions to improve in developing countries with rising incomes and better diets and living conditions, in a resource-constrained environment it would be invaluable for health policymakers to have better information about specific linkages between childhood conditions and adult morbidity and mortality so that development strategies could be formulated that would maximize the health gains to the population. In this context, as noted in this paper as well as in the review by Elo and Preston (1992), such health policies and programs may be directed toward not only reducing the current burden of disease seen in developing countries, for example, by the introduction of hepatitis B vaccine, but also limiting the emergence of the “diseases of development” such as cardiovascular disease by promoting the maintenance or adoption of healthy dietary practices in infancy and childhood as economies grow. Given the potential magnitude of the health gains in populations that could be achieved by directing more attention to risks and exposures in childhood, the importance and need for far more research in this area should be self-evident. REFERENCES Barker, J.P., K.M.Godfrey, C.Fall, C.Osmond, P.D.Winter, and S.O.Shaheen 1991 Relation of birth weight and childhood respiratory infection to adult lung function and death from chronic obstructive airways disease. British Medical Journal 303:671–675. Barnum, H., and R.Greenberg 1993 Cancers. In D.T.Jamison and W.H.Mosley, eds., Disease Control Priorities in Developing Countries. New York: Oxford University Press for the World Bank. Beasley, R.P. 1982 Hepatitis B virus as the etiologic agent in hepatocellular carcinoma: Epidemiologic considerations. Hepatology 2(2):21S-26S. Beasley, R.P., L-Y.Hwang, C-C.Lin, and C-S.Chien 1981 Hepatocellular carcinoma and hepatitis B virus. Lancet 1129–1133.

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