The Revised WIC Food Package and Child Development: A Quasi-Experimental Study

Leveraging the science of early life predictability to inform policies promoting child health

Addressing the tremendous burden of early-life adversity requires constructive dialogues between scientists and policy makers to improve population health. Whereas dialogues focused on several aspects of early-life adversity have been initiated, discussion of an underrecognized form of adversity that has been observed across multiple contexts and cultures is only now emerging. Here we provide evidence for "why unpredictability?", including: 1. Evidence that exposures to unpredictability affect child neurodevelopment, with influences that persist into adulthood. 2. The existence of a translational non-human animal model of exposure to early life unpredictability that can be capitalized upon to causally probe neurobiological mechanisms. 3. Evidence that patterns of signals in the early environment promote brain maturation across species. 4. The uneven distribution of unpredictability across demographic populations that illuminates a possible focal point for enhancing health equity. We then outline the potential of unpredictability in terms of the "what"; that is, how might the concept of unpredictability be leveraged to inform policy? We emphasize the importance of interdisciplinary and community partnerships to the success of this work and describe our community-engaged research project. Finally, we highlight opportunities for the science of unpredictability to inform policies in areas such as screening, immigration, criminal justice, education, childcare, child welfare, employment, healthcare and housing.

Participatory Systems Thinking to Elucidate Drivers of Food Access and Diet Disparities among Minoritized Urban Populations

The purpose of this study was to use participatory systems thinking to develop a dynamic conceptual framework of racial/ethnic and other intersecting disparities (e.g., income) in food access and diet in Philadelphia and to identify policy levers to address these disparities. We conducted three group model building workshops, each consisting of a series of scripted activities. Key artifacts or outputs included qualitative system maps, or causal loop diagrams, identifying the variables, relationships, and feedback loops that drive diet disparities in Philadelphia, Pennsylvania. We used semi-structured methods informed by inductive thematic analysis and network measures to synthesize findings into a single causal loop diagram. There were twenty-nine participants with differing vantages and expertise in Philadelphia's food system, broadly representing the policy, community, and research domains. In the synthesis model, participants identified 14 reinforcing feedback loops and one balancing feedback loop that drive diet and food access disparities in Philadelphia. The most highly connected variables were upstream factors, including those related to racism (e.g., residential segregation) and community power (e.g., community land control). Consistent with existing frameworks, addressing disparities will require a focus on upstream social determinants. However, existing frameworks should be adapted to emphasize and disrupt the interdependent, reinforcing feedback loops that maintain and exacerbate disparities in fundamental social causes. Our findings suggest that promising policies include those that empower minoritized communities, address socioeconomic inequities, improve community land control, and increase access to affordable, healthy, and culturally meaningful foods.

Do studies evaluating early-life policy interventions fully adhere to the critical conditions of difference-in-differences? A systematic review

OBJECTIVES

To assess the reporting and methodological quality of early-life policy intervention papers that applied difference-in-differences (DiD) analysis.

STUDY DESIGN

Systematic review.

DATA SOURCES

Papers applying DiD of early-life policy interventions in high-income countries as identified by searching Medline, Embase and Scopus databases up to December, 2022.

STUDY ELIGIBILITY CRITERIA, PARTICIPANTS AND INTERVENTIONS

Studies evaluating policy interventions targeting expectant mothers, infants or children up to two years old and conducted in high income countries were included. We focused on seven critical conditions of DiD as proposed in a comprehensive checklist: data requirements, parallel trends, no-anticipation, standard statistical assumptions, common shocks, group composition and spillover.

RESULTS

The DiD included studies (n=19) evaluating early-life policy interventions in childhood development (n=4), healthcare utilisation and providers (n=4), nutrition programmes (n=3) and economic policies such as prenatal care expansion (n=8). Although none of the included studies met all critical conditions, the most reported and adhered to critical conditions were data requirements (n=18), standard statistical assumptions (n=11) and the parallel trends assumption (n=9). No-anticipation and spillover were explicitly reported and adhered to in two studies and one study, respectively.

CONCLUSIONS

This review highlights current deficiencies in the reporting and methodological quality of studies using DiD to evaluate early-life policy interventions. As the validity of study conclusions and consequent implications for policy depend on the extent to which critical conditions are met, this shortcoming is concerning. We recommend that researchers use the described checklist to improve the transparency and validity of their evaluations. The checklist should be further refined by adding order of importance or knock-out criteria and may also help facilitate uniform terminology. This will hopefully encourage reliable DiD evaluations and thus contribute to better policies relating to expectant mothers, infants and children.

Understanding the Predictors of Low Take-Up of the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC): A Nationwide Longitudinal Study

INTRODUCTION

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) is among the largest U.S. social safety net programs. Although strong evidence exists regarding the benefits of WIC, take-up (i.e., participation among eligible individuals) has steadily declined in the past decade. This study addresses gaps in our knowledge regarding predictors of WIC take-up during this time.

METHODS

Data were drawn from the 1998-2017 waves of the National Health Interview Study (NHIS), a serial cross-sectional study of the U.S.

POPULATION

The analytic sample included 23,645 children and 10,297 women eligible for WIC based on self-reported demographic characteristics. To investigate predictors of WIC take-up, we regressed self-reported WIC receipt on a range of individual-level predictors (e.g., age, nativity, income) and state- level predictors (e.g., unemployment rate, governor's political affiliation) using multivariable logistic regression. In secondary analyses, results were additionally stratified by race/ethnicity, time period, and age (for children).

RESULTS

For both women and children, older maternal age and higher educational attainment were associated with decreased take-up of WIC. Associations differed by race/ethnicity, time period, and state characteristics including caseload of other social programs (e.g., Medicaid).

DISCUSSION

Our study identifies groups that are less likely to take up WIC benefits for which they are eligible, thereby contributing important evidence to inform programs and policies to increase WIC participation among groups with lower take-up. As WIC evolves past the COVID-19 pandemic, special attention will be needed to ensure that resources to encourage and support the participation of racially and economically marginalized individuals are equitably distributed.

A Systems Approach to Identify Factors Influencing Participation in Two Tribally-Administered WIC Programs

Native American populations experience highly disproportionate rates of poor maternal-child health outcomes. The WIC program aims to safeguard health by providing greater access to nutritious foods, but for reasons not well understood, participation in many tribally-administered WIC programs has declined to a greater extent compared to the national average decline in participation over the last decade. This study aims to examine influences on WIC participation from a systems perspective in two tribally-administered WIC programs. In-depth interviews were conducted with WIC-eligible individuals, WIC staff, tribal administrators, and store owners. Interview transcripts underwent qualitative coding, followed by identifying causal relationships between codes and iterative refining of relationships using Kumu. Two community-specific causal loop diagrams (CLDs) were developed and compared. Findings from interviews in the Midwest yielded a total of 22 factors connected through 5 feedback loops, and in the Southwest a total of 26 factors connected through 7 feedback loops, resulting in three overlapping themes: Reservation and Food Store Infrastructure, WIC Staff Interactions and Integration with the Community, and State-level Administration and Bureaucracy. This study demonstrates the value of a systems approach to explore interconnected barriers and facilitators that can inform future strategies and mitigate declines in WIC participation.

Effects of the revised WIC food package on women's and children's health: a quasi-experimental study

BACKGROUND

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) was revised in 2009 to be more congruent with national dietary guidelines. There is limited research examining effects of the revision on women's and children's health. The objective of this study was to evaluate whether the revised WIC food package was associated with various indicators of physical and mental health for women and children.

METHODS

We used 1998-2017 waves of the National Health Interview Survey (N = 81,771 women and 27,780 children) to estimate effects of the revised WIC food package on indicators of health for both women (self-reported health and body mass index) and children (anemia, mental health, and parent-reported health). We used difference-in-differences analysis, a quasi-experimental technique that assessed pre-post differences in outcomes among WIC-recipients while "differencing out" the secular underlying trends among a control group of non-recipients.

RESULTS

For all outcomes evaluated for women and children, we were unable to rule out the null hypothesis that there was no effect of receiving the revised WIC food package. These findings were confirmed across several secondary analyses conducted to assess heterogeneity of effects and robustness of results.

CONCLUSION

While we did not find effects of the revised WIC food package on downstream health indicators, studies using similarly robust methods in other datasets have found shorter-term effects on more proximal outcomes related to diet and nutrition. Effects of the modest WIC revisions may be less impactful on longer-term indicators of health, and future studies should examine the larger COVID-19-era expansion.

The effect of the 2009 WIC revision on maternal and child health: A quasi-experimental study

BACKGROUND

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) is the largest U.S. nutrition program for low-income pregnant women. It was revised in 2009, with the goal of improving nutritional content of food packages, enhancing nutrition education, and strengthening breast feeding support. Few studies have assessed the effects of this revision on perinatal health.

OBJECTIVES

To investigate the impact of the revised WIC program on maternal and child health in a large, multi-state data set.

METHODS

We conducted a quasi-experimental difference-in-differences analysis, comparing the pre/post changes among WIC recipients to changes among non-recipients. We adjusted for key sociodemographic covariates in multivariable linear models. We used data from the Pregnancy Risk Assessment Monitoring System (PRAMS) for 18 states from 2004 to 2017.

RESULTS

The main analysis included 331,946 mother-infant dyads. WIC recipients were more likely to be younger, Black or Hispanic/Latina, unmarried, and of greater parity. The revised WIC program was associated with reduced likelihood of more-than-recommended GWG (-1.29% points, 95% confidence interval [CI] -2.03, -0.56) and increased likelihood of ever breast fed (1.18% points, 95% CI 0.28, 2.08). We also identified heterogeneous effects on GWG, with more pronounced associations among women 35 and older. There were no associations with foetal growth.

CONCLUSIONS

The revised WIC program was associated with improvements in women's gestational weight gain and infant breast feeding.

The Special Supplemental Nutrition Program for Women, Infants, and Children food package revisions and anemia in children aged 2-5 years

BACKGROUND

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) provides nutritional assistance to low-income women and children in the United States. The WIC food package was revised to align more closely to dietary recommendations in October 2009. The revised package included more fruits, vegetables, whole grains, and low-fat milk.

OBJECTIVES

The objective of this study was to examine the association of the revised WIC package with anemia indicators and iron intake in children.

METHODS

A quasi-experimental difference-in-difference design compared anemia and iron intake variables between WIC (n = 1497 and n = 1626 for anemia and iron intake variables, respectively) and WIC-eligible nonparticipating children (n = 1183 and n = 1322 for anemia and iron intake variables, respectively), aged 2-5 y, before and after the 2009 revisions. The NHANES 2003-2008 and 2011-2018 data represented the period pre- and post-2009 revisions, respectively.

RESULTS

The 2009 package revisions were significantly associated with reduced probability of anemia (-4.3% points; 95% CI: -7.5, -1.1% points) and nonthalassemic microcytic anemia (-1.7% points; 95% CI: -3.3, -0.1% points) in children from WIC-participating households. The revised WIC package also was significantly related to higher nutrient adequacy ratio (0.04; 95% CI: 0.02, 0.07) and greater probability of meeting the RDA (12.1% points; 95% CI: 3.2, 21.0% points) for iron among WIC participants.

CONCLUSIONS

This study found that the WIC 2009 revisions were associated with lower probability of nonthalassemic microcytic anemia and better adequacy of dietary iron intake, thereby suggesting the beneficial impact of WIC revisions on iron deficiency anemia in children. The current study findings suggest that nutritional policies could play a crucial role in supporting the health of vulnerable children in the United States.

Impact of fruit and vegetable benefits on pregnancy outcomes among WIC participants: a natural experiment

Proper nutrition is critical for maternal and neonatal health. In January 2017, the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) in San Francisco, California, began providing an additional $40 per month in fruit and vegetable (F&V) benefits to pregnant clients with the goal of improving food security and nutrition-related outcomes. We evaluated whether pregnant women on WIC who received this additional F&V benefit exhibited better perinatal and birth outcomes compared with those who received standard WIC benefits. We used 2010-2019 birth certificate data from the National Center for Health Statistics. The intervention group consisted of WIC participants living in San Francisco (SF) County (intervention county) and whose first trimester started after January 2017. We used a quasi-experimental synthetic control method to compare trends between the intervention and control groups (a weighted sample of other California counties that did not distribute additional F&V benefits). Outcomes included low birth weight, preterm birth, small-for-gestational-age, gestational diabetes, and gestational weight gain. No significant differences in maternal and neonatal outcomes among WIC recipients in SF and synthetic control group were observed after the F&V benefits were distributed. Prior studies have shown that additional F&V benefits have positive effects on maternal and infant outcomes, indicating that F&V vouchers are a promising strategy for supporting equitable health outcomes. Our null results suggest that more rigorous research is needed to determine their optimal dose and duration, especially in high-cost-of-living areas, and to examine more upstream and structural interventions.

Participation in the Special Supplemental Nutrition Program for Women, Infants, and Children and Dietary Intake in Children: Associations With Race and Ethnicity

INTRODUCTION

Establishing healthy dietary intake in pediatric populations is important for prevention of chronic disease across the lifespan. Federal nutrition assistance programs can support the dietary intake of U.S. children. The objective of this study was to assess the relationship between Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) participation status and dietary intake within racial and ethnic groups.

METHODS

Dietary intake of children aged 2-4 years in the cross-sectional National Health and Nutrition Examination Survey 2011-2016 was analyzed in 2021. Multivariable linear regression was used to compare stratum-specific mean estimates for nutrient and food group intake of children participating in Special Supplemental Nutrition Program for Women, Infants, and Children (reference group) with those of nonparticipants who were income eligible and income ineligible (i.e., above income limits) for the WIC program. Significance was set to Bonferroni-corrected p-values.

RESULTS

Hispanic WIC participants consumed less added sugar (8.9 [SE=0.5] teaspoons) than their higher-income counterparts (14.6 [SE=1.5] teaspoons, p<0.001). Hispanic WIC participants also consumed more fiber (13.0 [SE=0.6] grams) than income-eligible (11.4 [SE=0.7] grams, p=0.032) and income-ineligible (i.e., higher-income, 9.4 [SE=1.3] grams, p=0.019) nonparticipants, but this was not significant at the Bonferroni-adjusted p-value of 0.01. No differences in dietary intake were observed by WIC participation status for non-Hispanic White and non-Hispanic Black children.

CONCLUSIONS

Participation in WIC was associated with healthier dietary outcomes among Hispanic children; however, dietary intake of White and Black children was comparable by WIC participation status. Federal nutrition assistance programs should support sound nutrition, an important factor in reducing the risk of chronic disease, in all groups.

WIC Participation and Dietary Quality among US Children: Impact of the 2009 Food Package Revision

This study aims to assess the effectiveness of the WIC program at improving children's dietary quality and to evaluate whether the 2009 food benefit revision further improved the WIC program. A sample of 1,753 children aged between 2 to 4 years from the 2005-2008 and 2011-2016 NHANES was analyzed using a propensity score weighted difference-in-difference approach. Results show that WIC-participating children scored 2.98 points higher (SD: 0.89; P<0.01) in HEI-2015 total scores compared with income-eligible non-participants during 2011-2016. No significant change was observed in the differences of HEI-2015 scores between WIC participants and eligible non-participants from 2005-2008 to 2011-2016.