Early childhood origins of the income/health gradient: The role of maternal health behaviors
Introduction
Several recent studies have documented a positive relationship between family income and child health in the US, Canada, and the UK (Case, Lubotsky, & Paxson, 2002; Chen, Martin, & Matthews, 2006; Currie, Shields, & Price, 2007; Currie & Stabile, 2003), with two of these studies finding that the slope of the “gradient” between family income and child health becomes steeper as children get older. With strong evidence for the existence of socioeconomic gradients in child health that begin early in life, it is important to identify the mechanisms through which children acquire the double disadvantage of poor socioeconomic status and poor health.
This paper builds upon previous work on the income gradient in child health by testing whether health risks during pregnancy and early infancy can explain the observed relationship between family income and children's health in the US. The paper employs unique data detailing the mother's health and behaviors during pregnancy and the child's early infancy, allowing a more comprehensive examination of the physical origins of the gradient in young children than has been previously carried out.
Section snippets
Background
While many studies have examined the relationship between socioeconomic status, especially poverty, and poor birth outcomes (Fairley & Leyland, 2006; Finch, 2003; Kramer, Seguin, Lydon, & Goulet, 2000), fewer have examined the nature of the income gradient in children's health beyond birth and how this gradient compares to the gradient in adults. Educational and income gradients for self-rated health, depression, and obesity in adolescents were found using data from the National Longitudinal
Sample
Data for this analysis come from the 1988 National Maternal and Infant Health Survey and 1991 Follow-up (NMIHS). The 1988 NMIHS, conducted by the National Center for Health Statistics, represents the richest national data set drawn from vital records for investigating the determinants of negative pregnancy outcomes. The sample was drawn from the vital records of women in the US who had a pregnancy in 1988, with an oversample of black women due to their higher rates of poor birth outcomes and
Health
Health status of the child is a categorical measure reported by the mother for the child on a scale of 1–5, with 1=excellent, 2=very good, 3=good, 4=fair and 5=poor. This health outcome has been used to characterize the size and shape of the income gradient in child health in the US, Canada, and the UK (Case et al., 2002; Currie et al., 2007; Currie & Stabile, 2003). While this measure of health status has been a powerful predictor of future mortality and functional decline in adults (Idler &
Data analysis
Analyses were conducted with STATA statistical package 9.0 (Stata Corp., 2005), using weights to adjust for survey design effects including oversampling of certain groups. Logistic regression models were used to predict the dichotomous intrauterine and early childhood health environment variables. Ordered probit models were used to estimate the relationship between family income and health status of the child on a five-point scale with and without controls for other health variables as follows:
Results
Table 2, Table 3, Table 4 show the relationships between the measures of intrauterine and early childhood health environment and maternal income and education. Almost uniformly, higher income and education are associated with pregnancy conditions and behaviors that are known to promote healthier pregnancies and healthier babies. Since all of these health variables are significantly related to both the income and education of the mother, we next test whether these measures can explain the
Discussion and limitations
Our analysis shows that while variables associated with the quality of the intrauterine and early childhood environment are strongly associated with family income, they do not explain the relationship between family income and maternal-assessed health of the child on a five-point scale. Our results for the magnitude of the relationship between family income and children's health status in the NMIHS (−0.132) are very close to the estimate of Case et al. for children ages 0–3 in the NHIS (−0.115)
Conclusions
The US Department of Health and Human Services declared as one of the two major objectives of its Healthy People 2010 health promotion agenda, “to eliminate health disparities among different segments of the population”. This paper has confirmed recent findings that these disparities seem to begin very early in life, finding that family income is significantly associated with the maternal-assessed health status of children at age 3. From a policy perspective, it is imperative to understand the
Acknowledgments
The financial support from the Woodrow Wilson School of Public and International Affairs (Princeton University), Mathematica Policy Research, Inc., and the Robert Wood Johnson Foundation Health and Society Scholars Program at the University of Michigan during the writing and revision of this paper is acknowledged.
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