The lasting impact of childhood health and circumstance

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Abstract

We quantify the lasting effects of childhood health and economic circumstances on adult health, employment and socioeconomic status, using data from a birth cohort that has been followed from birth into middle age. Controlling for parental income, education and social class, children who experience poor health have significantly lower educational attainment, poorer health, and lower social status as adults. Childhood health and circumstance appear to operate both through their impact on initial adult health and economic status, and through a continuing direct effect of prenatal and childhood health in middle age. Overall, our findings suggest more attention be paid to health as a potential mechanism through which intergenerational transmission of economic status takes place: cohort members born into poorer families experienced poorer childhood health, lower investments in human capital and poorer health in early adulthood, all of which are associated with lower earnings in middle age—the years in which they themselves become parents.

Introduction

Recent research has documented that children born into poorer families fall into poorer health as they age. These children arrive at the doorstep of adulthood not only in poorer health but also with lower educational attainment, in part attributable to their poorer health. (Cose et al., 2002 provide evidence for the US, and Currie and Stabile, 2004 for Canada.) This research suggests that childhood health may be an important contributor to the “gradient”, the widely documented positive association between good health and higher economic status observed in adulthood (Adler et al., 1994).

Research on determinants of adult health has varied in the weight it has placed on childhood health and circumstances. A strand of recent work suggests that nutrition in utero can affect health status in middle age, through its impact on such important chronic conditions as coronary heart disease and diabetes (Barker, 1995, Ravelli et al., 1998). New experimental work finds that mice whose fetal growth is restricted, but who are fed well after birth, exhibit rapid catch-up growth but die significantly earlier than mice well fed in utero (Ozanne and Hales, 2004). Children born to poor parents may be more likely to have had a poor fetal environment, leading to poor health in middle age. Having been raised in poorer families, such children are also more likely to earn less when they reach adulthood, leading to a correlation between earnings and health. In this way, the fetal-origins hypothesis could explain the positive association found between adult health and economic circumstance.

In a similar vein, some life course models emphasize the extent to which illness and deprivation in childhood have lasting effects on adult health—directly, through the illness itself, and indirectly, by restricting educational attainment and life chances (Kuh and Wadsworth, 1993). Life course models may also help to explain contemporaneous correlation between social status and health: those who have suffered chronic health conditions in childhood may reach adulthood in poorer health, and with less education and poorer labor market skills. Persistence in the processes generating earnings and health could lead to a contemporaneous correlation in earnings and health in adulthood that was due to conditions in childhood. Economists have contributed to this literature, examining the role played by health in education and labor market outcomes (see Currie and Madrian, 1999, for a review of the economics literature linking health to labor market outcomes, and Currie and Hyson, 1999, for an examination of the impact of low birthweight on educational attainment and labor market outcomes).

In contrast to these approaches, research centered on the role of adult socioeconomic status in determining adult health has largely argued that the observed correlation between income and health in adulthood is not directly attributable to childhood events. For example, Marmot et al. (2001) discuss their finding of a gradient in health among the subset of British civil servants whose parents survived to age 70. They conclude that, in their data, “early-life circumstances are important because they influence adult social circumstances, which in turn influence disease risk” (p. 305). Such pathways models posit a causal link from low socioeconomic status earlier in adulthood to poor health later in adulthood, with childhood circumstances important because they affect initial adult socioeconomic position.

In this paper, we quantify the lasting effects of childhood health and economic circumstances on adult health, employment and socioeconomic status, using data from a birth cohort that has been followed from birth into middle age. Making progress in this area is difficult for several reasons. Few datasets track individuals from childhood into adulthood. Much of what is known about the dynamics of income and health status for the US comes from a survey of the elderly, which restricts analysis to changes in income, wealth, and health status at the end of life, and over a short period of time.3 Panel data exist for the UK for three birth cohorts—the 1946 National Survey of Health and Development (NSHD), the 1958 National Child Development Study (NCDS, Centre for Longitudinal Studies, Bedford Group for Lifecourse and Statistical Studies, Institute of Education, http://www.cls.ioe.ac.uk/), and the 1970 British Cohort Study—and for two panels of British civil servants (the Whitehall I and II studies). However, these offer a more limited entry into the question than may first appear to be the case. Data from the 1946 cohort study are not publicly available, which restricts the extent to which any consensus could be reached using these data. The 1970 cohort is too young yet to trace childhood events very far into middle age. The Whitehall studies, which collected information on health and mortality of cohorts of British civil servants over time during working adulthood, contain only minimal retrospective information on family background. Results presented below suggest that, in particular, the lack of information on mother's education and own-health status in childhood limits the usefulness of the Whitehall data for quantifying the extent to which childhood circumstances can explain the relationship between health and economic status in adulthood.4 At the present time, the 1958 NCDS cohort provides the best opportunity to follow children across the bridge from childhood to adulthood.

There are difficulties in identifying causal relationships between health and socioeconomic status, even with the sort of rich, detailed data available for the NCDS. Unobserved factors, such as early-life experiences or genetic endowments, may drive both health and economic status over time. Experiments in which factors that affect economic status or health in early life are randomly altered may settle issues of causality, but the long-run impact of early-life nutrition and health interventions in some of the cleverly devised experiments being run today (Thomas et al., 2003, Gertler and Boyce, 2001) will not be fully realized for another 40 or 50 years.

Given the difficulties of drawing causal inferences, we proceed in two steps. Using data from the NCDS, we first present reduced form models that lay out the facts on the associations between childhood health and circumstance, on one hand, and educational attainment, adult health and socioeconomic status on the other. We then present more speculative estimates of the pathways through which prenatal and childhood health affect adult health and circumstance, making plain the assumptions necessary to attribute causal effects to different pathways.

We find, controlling for parental income, education and social class, that children who have experienced poorer uterine environments and poorer health in childhood have significantly lower educational attainment, poorer health and lower socioeconomic status as adults. Moreover, prenatal and childhood health appear to have direct effects on health and economic status in middle age: controlling for educational attainment, and for socioeconomic status and health in earlier adulthood, we find prenatal and childhood health markers are significant predictors of health and economic status at age 42.

Overall, our findings suggest more attention be paid to health as a potential mechanism through which intergenerational transmission of economic status takes place: cohort members born into poorer families experienced poorer childhood health, lower investments in human capital and poorer health in adulthood, all of which are associated with a lower probability of employment and lower earnings in middle age—the years in which they themselves become parents.

Section snippets

The 1958 National Child Development Study

The NCDS has followed all children born in Great Britain (Scotland, England and Wales) in the week of March 3, 1958 from birth through to age 42. Parents were interviewed at the time of the birth, and medical, social, demographic and economic data have been collected on these children during follow-up interviews conducted at ages 7, 11, 16, 23, 33 and 42.5

Educational attainment

Table 2 examines the relationship between childhood health and human capital investment. While the table focuses on the total number of O-level exams the child has passed by age 16, estimates of models for other educational outcomes—passing the English O-level, the Math O-level, and highest educational achievement—yield very similar results. In all cases, there is a significant association between health in childhood and educational attainment. On average, each childhood condition at age 7 is

Empirical framework

Our results in Section 3 show large, positive and significant associations of health in childhood with educational attainment, adult health, employment and social status. As we emphasized in Section 1, the interpretation of these findings requires caution: in the absence of experimental evidence, it is impossible to rule out that these associations are driven by unobserved “third factors” that influence both childhood health and adult circumstances. However, the fact that the associations

Conclusions

Our evidence suggests a potentially important role for all three models introduced earlier. Consistent with life-course models of health, childhood health conditions have a lasting impact on health and socioeconomic status in middle adulthood. Consistent with the fetal origins hypothesis, the uterine environment appears to play a significant role as a health determinant in middle age. The impact of the uterine environment is not reduced by controls for childhood health, educational attainment,

Acknowledgement

We thank Angus Deaton and Jeff Kling for useful discussions, and Janet Currie, Helen Levy, seminar participants at several universities and an anonymous referee for useful comments. This research has been funded in part through NIH grant R01 HD41141-01(National Institute for Child Health and Development). Fertig acknowledges support from a MacArthur Foundation postdoctoral fellowship while writing this paper.

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    Present address: Wylie Hall, Room 105, Indiana University, Bloomington, IN 47405, USA.

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    Present address: 316 Wallace Hall, Princeton University, Princeton, NJ 08544, USA.

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