Breastfeeding is one of the most effective ‘interventions’ for reducing infant mortality. Despite ongoing efforts to promote breastfeeding, current breastfeeding rates in the U.S. are still low, and socioeconomic and racial/ethnic disparities in breastfeeding practices have persisted. Improving breastfeeding practices among socially disadvantaged groups remains challenging. The goal of this dissertation is to improve breastfeeding rates and reduce racial/ethnic disparities in breastfeeding practices in the United States. Specifically, this dissertation aims to: (1) assess the influences of breastfeeding support from family, hospitals and workplaces on breastfeeding duration; (2) determine the extent to which racial/ethnic disparities in breastfeeding duration could be explained by breastfeeding support; and (3) estimate the population impact of multifaceted breastfeeding promotion interventions. Using data on approximately 4,000 mothers enrolled in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC), from the triennial Los Angeles County WIC Survey (2014, 2017), this dissertation found that breastfeeding support from family, hospitals and workplaces was significantly associated with longer breastfeeding duration, and that Black mothers and English-speaking Latina mothers have significantly lower breastfeeding rates than White mothers, with the difference widening over increasing duration. Results from causal mediation analysis (specifically, g-computation) showed that lack of access to breastfeeding support from family, hospitals and workplaces accounted for approximately two-thirds of the difference in breastfeeding duration between White and Black mothers, and one-third of the difference between White and English-speaking Latina mothers. This dissertation also illustrated the use of agent-based modeling (ABM) for estimating the population impact of five selected breastfeeding promotion interventions (improving knowledge, implementing Baby-Friendly Hospital Initiative practices, providing breastfeeding counseling, strengthening family support, and fostering supportive workplace environments) implemented singly or in combination with each other. The ABM demonstrated that while improving knowledge and increasing the availability of Baby-Friendly Hospital Initiative practices improve breastfeeding initiation rates, breastfeeding counseling, family support and a supportive workplace environment are more effective in improving breastfeeding duration. Increasing the coverage of multiple interventions simultaneously had a synergistic effect on breastfeeding duration, with their effects being greater than the additive effects of increasing the coverage of these interventions singly.

Background: Sugar-sweetened beverage (SSB) consumption has markedly increased in the last three decades among U.S. children and adolescents aged 2-18 years. The health effects of SSBs have mostly been examined in the context of obesity, and other metabolic disorders but little is known about how SSBs affect cognitive function. Evidence from animal and human studies suggests that high-fructose corn syrup and sucrose, found in large quantities in SSBs, may have adverse effects on the hippocampus, the learning and memory center of the brain. Nutritional insults to the hippocampus impair cognitive function and may negatively affect children's academic performance (AP). Purpose: The objectives were to examine the association between SSB consumption and AP in school-aged children, and identify modifiable food-related family behaviors associated with high SSB consumption. Methods: Data were obtained from an evaluation of a district wide multi-component school-based intervention which followed 238 fourth and fifth grade students annually from 2006 to 2009. Repeated measures analysis using mixed-effects models was conducted to examine the association between SSB consumption and AP measured by Math and English test scores; race, gender, grade level, mother `s education, mother's employment, intervention level and physical activity were controlled for. Mediation analysis was conducted to determine if family meal behaviors, namely the frequency with which children assist in meal preparation and have dinner with their family, mediate the association between socio-demographic variables and SSB consumption. Results: SSB consumption was inversely associated with English z-score (p<0.05); for every 24-ounces of soda consumed per day, English z-score decreased by 0.19 standard deviation units (3-4% of the mean). African American children had dinner together with their family less frequently than White children (p<0.01) and that as frequency of eating family dinner increased, SSB consumption decreased (p<0.05 among African Americans). Furthermore, African-American children assisted with meal preparation significantly more frequently than White children (p<0.01) but assisting with meal preparation was not significantly related to SSB consumption. Conclusion: SSB consumption is inversely associated with English but not math test score. The association between sociodemographic characteristics and SSB consumption is partially mediated by family meal behaviors. Future studies should explore how SSB consumption may affect cognitive function throughout the life-course and provide a clearer understanding of the biological mechanisms by which SSB consumption may influence AP.

Background

Given the rapid pace of urbanization and Westernization and the increasing prevalence of obesity, there is a need for research to better understand the influence of the built environment on overweight and obesity in world’s developing regions. Culturally-specific food environment survey instruments are important tools for studying changing food availability and pricing. Here, we present findings from an effort to develop and evaluate food environment survey instruments for use in a rapidly developing city in southwest China.

Methods

We developed two survey instruments (for stores and restaurants), each designed to be completed within 10 minutes. Two pairs of researchers surveyed a pre-selected 1-km stretch of street in each of three socio-demographically different neighborhoods to assess inter-rater reliability. Construct validity was assessed by comparing the food environments of the neighborhoods to cross-sectional height and weight data obtained on 575 adolescents in the corresponding regions of the city.

Results

273 food establishments (163 restaurants and 110 stores) were surveyed. Sit-down, take-out, and fast food restaurants accounted for 40%, 21% and 19% of all restaurants surveyed. Tobacco and alcohol shops, convenience stores and supermarkets accounted for 25%, 12% and 11%, respectively, of all stores surveyed. We found a high percentage of agreement between teams (>75%) for all categorical variables with moderate kappa scores (0.4-0.6), and no statistically significant differences between teams for any of the continuous variables. More developed inner city neighborhoods had a higher number of fast food restaurants and convenience stores than surrounding neighborhoods. Adolescents who lived in the more developed inner neighborhoods also had a higher percentage of overweight, indicating well-founded construct validity. Depending on the cutoff used, 19% to 36% of male and 10% to 22% of female 16-year old adolescents were found to be overweight.

Conclusions

The prevalence of overweight Chinese adolescents, and the food environments they are exposed to, deserve immediate attention. To our knowledge, these are the first food environment surveys developed specifically to assess changing food availability, accessibility, and pricing in China. These instruments may be useful in future systematic longitudinal assessments of the changing food environment and its health impact in China.

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The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) serves 50% of infants and 25% of preschool-aged children in the U.S. and collects height and weight measurements from eligible children every six months, making WIC data a valuable resource for studying childhood growth and obesity.  We assessed the accuracy of measurements collected by WIC staff by comparing them to “gold standard” measurements collected by trained research staff.  At seven WIC clinics in southern California, 287 children ages 2-5 years measured by WIC staff using WIC standard protocol were re-measured by research staff using a research protocol (duplicate measurements with shoes and outerwear removed taken by trained personnel).  Intraclass correlation coefficients measuring agreement between WIC and research protocol measurements for height, weight and body mass index (BMI) were 0.96, 0.99 and 0.93, respectively.  Although WIC measurements overestimated height by 0.6 cm and weight by 0.05 kg on average, BMI was underestimated by only 0.15 kg/m² on average.  WIC BMI percentiles classified children as overweight/obese versus underweight/normal with 86% sensitivity and 92% specificity.  We conclude that height, weight and BMI measurements of children aged 2-5 years collected by trained WIC staff are sufficiently accurate for monitoring and research purposes.

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