Economic hardship in childhood and adult health trajectories: An alternative approach to investigating life-course processes

The importance of community resources for breastfeeding

BACKGROUND

Breastfeeding has long-lasting effects on children's cognition, behavioral, mental and physical health. Previous research shows parental characteristics (e.g., education, race/ethnicity, income level) are associated with breastfeeding initiation and duration. Further, research shows significant variation in access to community resources by race/ethnicity. It is unclear how community resources may impact breastfeeding practices and how this might intersect with maternal race/ethnicity.

METHODS

This study combined nationally-representative data from the Study of Attitudes and Factors Effecting Infant Care (SAFE), which surveyed US mothers immediately after the infant's birth and at two to six months of infant age, with the Child Opportunity Index (COI) 2.0, a census tract measure of community resources associated with child development, to explore the association between community resources and breastfeeding initiation and whether this varies based on maternal race/ethnicity and country of birth. The SAFE Study used a stratified, two-stage, clustered design to obtain a nationally representative sample of mothers of infants, while oversampling Hispanic and non-Hispanic (NH) Black mothers. The SAFE study enrolled mothers who spoke English or Spanish across 32 US birth hospitals between January 2011 and March 2014.

RESULTS

After accounting for individual characteristics, mothers residing in the highest-resourced communities (compared to the lowest) had significantly greater likelihood of breastfeeding. Representation in higher-resourced communities differed by race/ethnicity. Race/ethnicity did not significantly moderate the association between community resources and breastfeeding. In examining within race/ethnic groups, however, community resources were not associated with non-US born Black and Hispanic mothers' rates of breastfeeding, while they were with US born Black and Hispanic mothers.

CONCLUSIONS

Findings suggest that even health behaviors like breastfeeding, which we often associate with individual choice, are connected to the community resources within which they are made. Study implications point to the importance of considering the impact of the contextual factors that shape health and as a potential contributor to understanding the observed race/ethnicity gap.

The Long Arm of Prospective Childhood Income for Mature Adult Health in the United States

Pioneering scholarship links retrospective childhood conditions to mature adult health. We distinctively provide critical evidence with prospective state-of-the-art measures of parent income observed multiple times during childhood in the 1970s to 1990s. Using the Panel Study of Income Dynamics, we analyze six health outcomes (self-rated health, heart attack, stroke, life-threatening chronic conditions, non-life-threatening chronic conditions, and psychological distress) among 40- to 65-year-olds. Parent relative income rank has statistically and substantively significant relationships with five of six outcomes. The relationships with heart attack, stroke, and life-threatening chronic conditions are particularly strong. Parent income rank performs slightly better than alternative prospective and retrospective measures. At the same time, we provide novel validation on which retrospective measures (i.e., father's education) perform almost as well as prospective measures. Furthermore, we inform several perennial debates about how relative versus absolute income and other measures of socioeconomic status and social class influence health.

Intergenerational Social Mobility and Allostatic Load in Midlife and Older Ages: A Diagonal Reference Modeling Approach

OBJECTIVES

This study aims to understand the association of life-course intergenerational social mobility with allostatic load (AL) burden in midlife and older ages in Ireland.

METHODS

The study involved biological data for 3,987 older adults participating in The Irish Longitudinal Study on Ageing (TILDA). Intergenerational social mobility was characterized using the cross-classification of origin socioeconomic position (SEP; i.e., father's occupation) and destination SEP (i.e., own occupation). AL was operationalized using 12 biomarkers tapping cardiovascular, metabolic, renal, and immune system dysregulation. Diagonal reference modeling (DRM) and ordinary least square regression techniques were applied to explore the effect of social mobility on AL burden.

RESULTS

A total of 55.5% experienced intergenerational mobility: 37.5% were upwardly mobile, 18.0% were downwardly mobile. A social gradient in AL was observed among the socially non-mobile. Destination SEP (b = 0.74, 95% CI = 0.57, 0.92) predominated in influence over origin, although both life stages exerted significant influence on later-life AL. Social mobility in either direction was not associated with AL burden. Mobility coefficients were substantially small across a large variety of model specifications.

DISCUSSION

Findings provide evidence for an accumulation model of social inequalities in which disparities in health are diluted rather than increased by social mobility (i.e., gradient constraint), with the socially mobile having an AL score that is intermediate between their origin class and destination class. This implies that the effects of origin SEP on health are not immutable, but are instead responsive to changing socioeconomic circumstances across the life course.

Prenatal origins of suicide mortality: A prospective cohort study in the United States

Most suicide research focuses on acute precipitants and is conducted in high-risk populations. Yet, vulnerability to suicide is likely established years prior to its occurrence. In this study, we aimed to investigate the risk of suicide mortality conferred by prenatal sociodemographic and pregnancy-related factors. Offspring of participants (N = 49,853) of the Collaborative Perinatal Project, a U.S. population-based cohort of pregnancies enrolled between 1959 and 1966, were linked to the U.S. National Death Index to determine their vital status by the end 2016. We examined associations between sociodemographic factors during pregnancy, pregnancy complications, labor and delivery complications, and neonatal complications with suicide death coded according to ICD-9/10 criteria. By the end of 2016, 3,555 participants had died. Of these, 288 (214 males, 74 females) died by suicide (incidence rate = 15.6 per 100,000 person-years, 95% Confidence Interval [CI] = 13.9-17.5). In adjusted models, male sex (Hazard Ratio [HR] = 2.98, CI: 2.26-3.93), White race (HR = 2.14, CI = 1.63-2.83), low parental education (HR = 2.23, CI = 1.38-3.62), manual parental occupation (HR = 1.38, CI = 1.05-1.82), being a younger sibling (HR = 1.52, CI = 1.10-2.11), higher rates of pregnancy complications (HR = 2.36, CI = 1.08-5.16), and smoking during pregnancy (HR = 1,28, CI = 0.99-1.66) were independently associated with suicide risk, whereas birth and neonatal complications were not. Consistent with the developmental origins of psychiatric disorders, vulnerability to suicide mortality is established early in development. Both sociodemographic and pregnancy factors play a role in this risk, which underscores the importance of considering life course approaches to suicide prevention, possibly including provision of high-quality prenatal care, and alleviating the socioeconomic burdens of mothers and families.

Lifetime socioeconomic determinants of health trajectories among older adults

Drawing on life course theory and research, we explored how socioeconomic circumstances during childhood and adulthood shape self-reported health trajectories among older Mexican adults. We used data from the Mexican Health and Aging Study panel survey (2001-2015) and used sequence analysis to estimate types of self-reported health trajectories in older adulthood. We then explored the association between those health trajectories and socioeconomic determinants at different life stages, including education, occupation, employment, economic status, parental education, and adverse living conditions and illnesses during childhood. Our contributions are threefold. First, we identified four types of health trajectories for men and eight for women, representing a more nuanced longitudinal health status profile than previously shown. Second, we found that childhood and adult socioeconomic circumstances influence self-reported health trajectories at older age. Third, our results suggest there is no simple monotonic relationship between life course circumstances and self-reported health trajectories.

The lasting imprint of childhood disadvantage: cumulative histories of exposure to childhood adversity and trajectories of psychological distress in adulthood

This study contributes to the literature on the long-term effects of childhood disadvantage on mental health by estimating the association between patterns of cumulative childhood adversity on trajectories of psychological distress in adulthood. There is little research that investigates how compositional variations in the accumulation of childhood adversity may initiate distinct processes of disadvantage and differentially shape trajectories of psychological distress across the adult life course. Using the Panel Study of Income Dynamics' Childhood Retrospective Circumstance Study and latent class analysis, we first identify distinct classes representing varied histories of exposure to childhood adversities using 25 indicators of adversity across multiple childhood domains. Next, the latent classes are included as predictors of trajectories of psychological distress in adulthood. The results demonstrate that patterns of experiences of childhood adversity are associated with higher levels of adult psychological distress that persists, and in some cases worsens, in adulthood, contributing to disparities in mental health across the life course.

Cumulative risk of compromised physical, mental and social health in adulthood due to family conflict and financial strain during childhood: a retrospective analysis based on survey data representative of 19 European countries

Background

Childhood adversity (CA) has previously been linked to various health problems in adulthood. Investigations into the differential impact of distinct types of CA on a wide range of outcomes are scarce. This study aimed to assess the impact of self-reported childhood family conflict and/or financial strain on health and social functioning in adulthood among Europeans, while taking into account the mediating role of adulthood socioeconomic disadvantage (SED) in these associations.

Methods

Using the European Social Survey (ESS) collected in 2014, nationally representative cross-sectional data from 35 475 participants aged 15 years and older in 19 European countries were analysed. Logistic regressions were conducted to assess associations of retrospectively reported family conflict and/or financial strain in childhood with physical and mental health as well as health behaviours and social functioning in adulthood.

Results

A quarter of the European population reported having experienced family conflict, financial strain or both in childhood. Financial strain was reported more among older age groups and conflict more among younger age groups. A dose-response pattern with increased risk was demonstrated for almost all physical, behavioral, mental and social outcomes for these aspects of CA compared with no CA, with the highest risk observed in those who experienced both financial strain and family conflict. Adulthood SED mediated a significant proportion of the associations with financial strain (ranging from 5.4% to 72.4%), but did not mediate the associations with conflict.

Conclusion

Individuals reporting family conflict or financial strain during childhood are at increased risk of developing a wide range of health and social problems. Those who report financial strain in childhood are more likely to experience SED in adulthood, which in turn increases their risk of experiencing health and social problems. Reported family conflict during childhood conferred increased risk of health and social problems, but adulthood SED did not appear to operate as an indirect pathway.

Low income dynamics and depression over the life course in South Korea

OBJECTIVES

We examined how experiencing low income multiple times is associated with depressive symptoms over the life course to better understand the influence of low income experience on psychological well-being.

METHODS

We employed fixed effects models to estimate the association between low income experience and depressive symptoms using data from a longitudinal survey of a representative sample of adults in Korea (N=6,930). We also considered age variations given different perspectives and social circumstances related to different ages and family stages over the life course that potentially modify the association.

RESULTS

Our results revealed that the detrimental influence of low income experience on depressive symptoms slowly declines with additional increments in the number of the exposures. Additionally, although older adults have a higher risk of experiencing low income more than once, the detrimental influence appears more salient among younger adults compared to older individuals.

DISCUSSION

We offered some explanations for the diminishing effects of additional experiences of low income on depressive symptoms, and the age group variations in the association in Korea. We also discussued policy implications of our findings.

Adverse Childhood Experiences and Physical and Mental Health of Adults: Assessing the Mediating Role of Cumulative Life Course Poverty

OBJECTIVES

Research has linked adverse childhood experiences (ACEs) to a host of negative health outcomes in adulthood. However, most existing studies focused on traumatic ACEs and used samples collected from a specific geographic unit (e.g., region, city, or state). This study examines the association between non-traumatic ACEs and health outcomes (i.e., self-rated health and psychological well-being) in adulthood, and assesses the extent to which the cumulative life course poverty accounts for these associations between ACEs and health.

DATA SOURCE

Public and de-identified data from Panel Study of Income Dynamics (PSID) (1968-2013) and its Childhood Retrospective Circumstances Study (CRCS) (2014) (N = 7,126) were used. Episode and severity of childhood adversities of respondents were determined by using comprehensive retrospective circumstance measures.

METHODS

Multivariate regression models were used to analyze the associations between ACEs and adult health. Mediation analysis was employed to assess the extent to which the associations were explained by cumulative life course poverty. Data analysis was carried out in 2019 using STATA 15.

RESULTS

We found that episode and severity of ACEs were associated with increased risk of poor health and psychological distress. Compared to individuals with no ACEs, one unit increase in the ACE index is associated with 8 and 18 percent increase in the risk of poor health and psychological distress, respectively. A small proportion (4%) of the impact of early adversities on health is attributable to the proportion of adult lifetime spent in poverty.

CONCLUSIONS

Non-traumatic ACEs are associated with increased risk for poor health and psychological distress. Life course cumulative experience in poverty accounts for a small portion of the associations. Providing support to prevent ACEs may have long-term health benefits.

Understanding Racial/Ethnic Disparities in Physical Performance in Midlife Women: Findings From SWAN (Study of Women's Health Across the Nation)

OBJECTIVES

Evaluate degree to which racial/ethnic differences in physical performance are mediated by sociodemographic, health, behavioral, and psychosocial factors.

METHODS

Physical performance was evaluated using a decile score derived from grip strength, timed 4 m walk, and timed repeat chair stand in 1,855 African American, Caucasian, Chinese, Hispanic, and Japanese women, mean age = 61.8 (SD = 2.7) in the Study of Women's Health Across the Nation. Mediators included education, financial strain, comorbidities, pain, body mass index (BMI), physical activity, and perceived stress. Structural equation models provided estimates of the total difference in physical performance between Caucasians and each race/ethnic groups and differences due to direct effects of race/ethnicity and indirect effects through mediators.

RESULTS

The mean decile score for Caucasian women was 16.9 (SD = 5.6), 1.8, 2.6, and 2.1 points higher than the model-estimated scores in African Americans, Hispanics and Chinese, respectively, and 1.3 points lower than the Japanese. Differences between Caucasians and the Chinese and Japanese were direct effects of race/ethnicity whereas in African Americans and Hispanics 75% or more of that disparity was through mediators, particularly education, financial strain, BMI, physical activity, and pain.

DISCUSSION

Addressing issues of poverty, racial inequality, pain, and obesity could reduce some racial/ethnic disparity in functional limitations as women age.

Childhood peer status and circulatory disease in adulthood: a prospective cohort study in Stockholm, Sweden

OBJECTIVES

Childhood conditions have been recognised as important predictors of short-term and long-term health outcomes, but few studies have considered status position in the peer group as a possible determinant of adult health. Lower peer status, which often reflects experiences of marginalisation and rejection by peers, may impose inequality experiences and leave long-lasting imprints on health. The present study aimed to examine whether peer status is associated with the risk for circulatory disease in adulthood.

DESIGN

Prospective cohort study based on the Stockholm Birth Cohort Multigenerational Study(SBC Multigen).

SETTING

Stockholm metropolitan area.

PARTICIPANTS

All individuals who were born in 1953 and resident in the greater metropolitan area of Stockholm in 1963 (n=14 608). The analytical sample consisted of 5410 males and 5990 females. Peer status was sociometrically assessed in cohort members at age 13. The survey material was linked to inpatient care registers that contained information about circulatory diseases (n=1668) across ages 20-63. Cox proportional hazard models were used for the analysis.

OUTCOME MEASURE

Circulatory disease.

RESULTS

Peer marginalisation at age 13 resulted in significantly higher risks of circulatory disease in adulthood among males (HR 1.34; 95% CI 1.09 to 1.64) and females (HR 1.33; 95% CI 1.04 to 1.70) alike. A graded relationship between peer status and circulatory diseases was detected in females (p=0.023). Among males there was a threshold effect, showing that only those in the lowest status position had significantly increased risks of circulatory disease. The associations remained significant after adjusting for various conditions in childhood and adulthood.

CONCLUSIONS

This study shows that circulatory diseases in adulthood may be traceable to low peer status and marginalisation in childhood. It is suggested that peer status in late childhood may precede social integration in adolescence and adulthood, acting as a long-term stressor that contributes to circulatory disease through biological, behavioural and psychosocial pathways.

Looking homeward with the life course: Early origins of adult dwelling satisfaction?

The long-term influence of childhood economic and social exposures on adult health and well-being is well-known. Most childhood circumstances transpire in or near the home, yet research has largely neglected how early exposures shape people's experience of their residential context in adulthood. To help address this gap, we use retrospective longitudinal data from the Midlife Development in the United States (MIDUS) study. Drawing on a life course framework, we test the potential mediating roles of adult social, economic, and mental health processes. Results suggest that childhood parental warmth and maltreatment have an enduring influence on people's satisfaction with their adult home, while there is little indication that childhood economic conditions shape adult dwelling satisfaction. Analyses of average controlled direct effects suggest that the effects of childhood parental warmth are mediated slightly by adult socioeconomic attainment and psychological adjustment but especially by supportive family relationships during adulthood. This pattern is consistent with an attachment-based interpretation of the importance of childhood conditions for adult relationships as well as home satisfaction. Taken together, our results suggest that parent-child bonds cast a long shadow over how people experience their residential context decades later, through a diffuse, multifaceted set of intervening pathways.

Trajectories of childhood adversity and the risk of depression in young adulthood: Results from the Avon Longitudinal Study of Parents and Children

BACKGROUND

The significance of the timing and chronicity of childhood adversity for depression outcomes later in life is unclear. Identifying trajectories of adversity throughout childhood would allow classification of children according to the accumulation, timing, and persistence of adversity, and may provide unique insights into the risk of subsequent depression.

METHODS

Using data from the Avon Longitudinal Study of Parents and Children, we created a composite adversity score comprised of 10 prospectively assessed domains (e.g., violent victimization, inter-parental conflict, and financial hardship) for each of eight time points from birth through age 11.5 years. We used semiparametric group-based trajectory modeling to derive childhood adversity trajectories and examined the association between childhood adversity and depression outcomes at the age of 18 years.

RESULTS

Among 9,665 participants, five adversity trajectories were identified, representing stable-low levels (46.3%), stable-mild levels (37.1%), decreasing levels (8.9%), increasing levels (5.3%), and stable-high levels of adversity (2.5%) from birth through late childhood. Approximately 8% of the sample met criteria for probable depression at 18 years and the mean depression severity score was 3.20 (standard deviation = 3.95, range 0-21). The risk of depression in young adulthood was elevated in the decreasing (odds ratio [OR] = 1.72, 95% confidence interval [CI] = 1.19-2.48), increasing (OR = 1.81, 95% CI = 1.15-2.86), and stable-high (OR = 1.80, 95% CI = 1.00-3.23) adversity groups, compared to those with stable-low adversity, when adjusting for potential confounders.

CONCLUSIONS

Children in trajectory groups characterized by moderate or high levels of adversity at some point in childhood exhibited consistently greater depression risk and depression severity, regardless of the timing of adversity.

Early life adversity increases the salience of later life stress: an investigation of interactive effects in the PSID

A large body of evidence has shown that stress throughout life is associated with health trajectories, but the combination of adverse experiences at different stages of the life course is not yet well understood. This study examines the interactions between childhood adversity, adulthood adversity, and adult physical and mental health. Using data from The Childhood Retrospective Circumstances Study (CRCS) supplement to the Panel Study of Income Dynamics (PSID), we created indices of early life adversity (EAI) and adult adversity (AAI). We used logistic regression to examine the effects of EAI and AAI, adjusting for age, sex, race/ethnicity, health behaviors, and childhood health as covariates in all models. We repeated this analysis for the outcomes of fair/poor health, two or more chronic conditions, and psychological distress in adulthood. For all the three outcomes, our findings suggest increasing salience of adult adversity among those who experienced higher levels of early adversity. Individuals with high EAI and high AAI exhibited the highest odds of fair/poor health (OR = 5.71), chronic conditions (OR = 3.06), and psychological distress (OR = 13.08) compared to those with low EAI and low AAI. These findings are consistent with the accumulation of risk or dual risk model of stress and health. Adversity in childhood amplifies the health risks associated with stress in adulthood for multiple health outcomes.

More than a snapshot in time: pathways of disadvantage over childhood

Background

Disadvantage rarely manifests as a single event, but rather is the enduring context in which a child's development unfolds. We aimed to characterize patterns of stability and change in multiple aspects of disadvantage over the childhood period, in order to inform more precise and nuanced policy development.

Methods

Participants were from the Longitudinal Study of Australian Children birth cohort (n = 5107). Four lenses of disadvantage (sociodemographic, geographic environment, health conditions and risk factors), and a composite of these representing average exposure across all lenses, were assessed longitudinally from 0 to 9 years of age. Trajectory models identified groups of children with similar patterns of disadvantage over time for each of these lenses and for composite disadvantage. Concurrent validity of these trajectory groups was examined through associations with academic performance at 10-11 years.

Results

We found four distinct trajectories of children's exposure to composite disadvantage, which showed high levels of stability over time. In regard to the individual lenses of disadvantage, three exhibited notable change over time (the sociodemographic lens was the exception). Over a third of children (36.3%) were exposed to the 'most disadvantaged' trajectory in at least one lens. Trajectories of disadvantage were associated with academic performance, providing evidence of concurrent validity.

Conclusions

Children's overall level of composite disadvantage was stable over time, whereas geographic environments, health conditions and risk factors changed over time for some children. Measuring disadvantage as uni-dimensional, at a single time point, is likely to understate the true extent and persistence of disadvantage.

Education and Physical Health Trajectories in Later Life: A Comparative Study

The cumulative (dis)advantage hypothesis states that health disparities between education groups increase with age. The present study examined this hypothesis in a comparative analysis of the United States, the United Kingdom, the Netherlands, and Sweden. These countries offer sharp contrasts in the social conditions that may intensify or inhibit processes of cumulative (dis)advantage. Using harmonized panel data from the HRS, ELSA, and SHARE, the study applied Poisson multilevel regression models to trace changes in the number of chronic conditions and functional limitations of people aged 50–76 (N = 16,887 individuals; 71,154 observations). The four countries showed a clear gradient in levels of physical health and in the extent to which health trajectories were shaped by education. Across all ages and cohorts, health problems were most prevalent in the United States, less prevalent in the United Kingdom and the Netherlands, and least prevalent in Sweden. A similar cross-national gradient was found for the size of health gaps between education groups and for the extent to which these gaps widened with age. Gaps were largest in the United States, smaller in the United Kingdom and in the Netherlands, and smallest in Sweden.

Childhood poverty dynamics and adulthood overweight/obesity: Unpacking the black box of childhood

Integrating several life course models, this study examines how childhood poverty dynamics shape the risk of adulthood overweight/obesity. Growth mixture models of yearly poverty data from age 0-16 from the U.S. Panel Study of Income Dynamics identify four childhood poverty trajectories: chronic poverty, early childhood poverty, downward mobility, and poverty-free. Chronic poverty and early childhood poverty groups have higher risk of adulthood overweight/obesity than the poverty-free group. Overweight/obesity risk is not significantly different between the chronic poverty group and the early childhood poverty group, suggesting that the effects of early childhood exposure persist despite subsequent upward mobility. Downward mobility in the absence of early childhood poverty does not significantly increase adulthood obesity risk, providing further evidence that early childhood is a critical period for developing risk of overweight and obesity. These findings shed new light on the timing model, social mobility model, cumulative model, and cumulative inequality theory.

From "Buzzword" to Best Practice: Applying Intersectionality to Children Exposed to Intimate Partner Violence

Empirical studies on the impact of intimate partner violence (IPV) on children have burgeoned over the last three decades. Notably absent from existing approaches to studying children exposed to IPV, however, is attention to how various positionalities intersect to impact the experiences of children and their families. In fact, while the importance of an intersectional framework for understanding IPV has been discussed for over two decades, little or no attention has been given to issues of children's exposure to IPV. In this article, we examine the current state of the literature on children exposed to IPV through an exploratory meta-analysis, finding limited application of intersectionality and a focus on discrete categories of difference. We then demonstrate why and how an intersectional framework should be applied to children exposed to IPV, with specific strategies for research and policy. We suggest a child-centered approach that recognizes diversity among children exposed to IPV, extending the challenge to traditional "one-size-fits-all" models to include an intersectionality-informed stance.

Childhood Socioeconomic Status and Stress in Late Adulthood: A Longitudinal Approach to Measuring Allostatic Load

Objectives: This study examines how the effects of childhood socioeconomic status (SES) may carry on into late adulthood. Methods: We examine how childhood SES affects both perceived stress and allostatic load, which is a cumulative measure of the body’s biologic response to chronic stress. We use the National Social Life, Health, and Aging Project, Waves 1 and 2, and suggest a novel method of incorporating a longitudinal allostatic load measure. Results: Individuals who grew up in low SES households have higher allostatic load scores in late adulthood, and this association is mediated mostly by educational attainment. Discussion: The longitudinal allostatic load measure shows similar results to the singular measures and allows us to include 2 time points into one outcome measure. Incorporating 2 separate time points into one measure is important because allostatic load is a measure of cumulative physiological dysregulation, and longitudinal data provide a more comprehensive measure.

Life Course Pathways of Economic Hardship and Mobility and Midlife Trajectories of Health

We utilize over 40 years of prospective data from the Panel Study of Income Dynamics (N = 1,229) and repeated-measures latent class analysis to examine how long-term patterns of stability and change in economic hardship from childhood to adulthood are related to subsequent trajectories of midlife health. We review conceptual and methodological approaches to examining health inequality across the life course and highlight the contribution of a person-centered, disaggregated approach to modeling health and its association with long-term pathways of economic resources, including changing resources associated with mobility. Findings suggest those who experienced early mobility out of economic hardship were less likely than those in persistent economic hardship to experience a high-risk health trajectory, while experiencing later mobility did not lessen this risk. We conclude with a call for further investigation into the role of social mobility and the timing, degree, and direction of change in investigations of health inequality.

Gains in income during early childhood are associated with decreases in BMI z scores among children in the United States

BACKGROUND

Evidence suggests that changes in family income are an important determinant of children's body mass index (BMI). However, few studies have leveraged longitudinal data to investigate the association of changes in family income on changes in BMI z score.

OBJECTIVE

This study aimed to assess whether gains in family income are associated with changes in BMI z score among children in the United States by using the nationally representative Early Childhood Longitudinal Survey Birth Cohort (ECLS-B).

DESIGN

We used longitudinal data from the ECLS-B to assess whether gains in family income, assessed by using the poverty to income ratio (PIR), were associated with changes in BMI z score among children aged 2-6 y. Child anthropometric characteristics and family income were assessed at 2-y, 4-y, 5-y, and 6-y visits. Sex-stratified, individual fixed-effects linear regression models compared children with themselves over time to control for time-invariant measured and unmeasured confounding factors. Models also controlled for time-varying confounders, including number of siblings, household structure (2 parents, one parent, or unrelated guardian), age, and age squared.

RESULTS

Children (n = ~9200) had a mean ± SE change in BMI z score of 0.12 ± 0.022, and family income increased by ~$3361 ± $536 during the 4-y period of observation (2003-2007). The association between increased PIR and change in BMI z score varied by sex but not by race-ethnicity. Among girls, an increase in PIR was associated with a statistically significant decrease in BMI z score (βPIR = -0.022; 95% CI: -0.042, -0.0016). There was a statistically significant association between PIR and BMI z score among preterm boys (βPIR + β PIRXpreterm = -0.067; 95% CI: -0.12, -0.018), but the relation was not statistically significant among boys born at term (βPIR = -0.0049; 95% CI: -0.024, 0.014).

CONCLUSIONS

By comparing children with themselves over time, we overcome many barriers that typically impede causal inference in observational studies. In this way, our study provides stronger evidence that gains in income during early childhood may promote healthy weight outcomes among girls.