Discussion
The results of this study show that 3-year obesity prevalence among 3- and 4-year old children enrolled in WIC in high-risk and low-risk neighborhoods in the Bronx, Brooklyn, and Manhattan declined from 2004–2006 to 2008–2010. The declines were greatest in high-risk neighborhoods of the Bronx and Manhattan, with average annual percentage changes that ranged from −4.7% in Manhattan to −2.6% in the Bronx. The findings suggest a narrowing of the gap in early childhood obesity prevalence between high-risk and low-risk neighborhoods in Manhattan and the Bronx, but not in Brooklyn where race/ethnicity shifts in low-risk neighborhoods were substantial. The observed narrowing of the gap between 3-year obesity prevalence in high-risk neighborhoods in Manhattan and the Bronx during 2008–2010 suggests that some progress is being made in addressing health disparities consistent with the mission of the New York City DPHOs.
The observed declines in 3-year obesity prevalence in the study neighborhoods from 2004–2006 to 2008–2010 are consistent with secular trends that show that obesity among preschool and school-aged children has plateaued, and with reports of declines in childhood obesity in different parts of the United States. The relationship of these findings to compliance with the Article 47 regulations by child care centers in the ICF New York City evaluation is unknown but may point to the importance of more intensive assistance in these areas of the city. Compliance with Article 47 of the New York City Health Code was expected in all city neighborhoods. It is likely that multiple factors influenced the decline in obesity rates.
This study shows that geographic variation in childhood obesity is significant within New York City neighborhoods. Evidence of neighborhood-level variation in childhood obesity prevalence in a large city such as New York City underscores the importance of identifying and monitoring modifiable aspects of the built and social environments when designing and implementing interventions and policies to support the maintenance of healthy lifestyles.
Because this study did not include measures of the built environment, it is not possible to comment on the extent to which the observed differences in 3-year obesity prevalence over time could be explained by within-neighborhood changes in socio-environmental characteristics. However, a previous analysis of census and New York City Community Health Survey data shows that more affluent neighborhoods in New York City tend to have more resources that support maintenance of physical activity and healthy eating behavior. Most importantly, that same analysis showed that prevalence of adult obesity was higher in less-resourced, low-income communities than in more affluent neighborhoods.
Beyond the built environment, however, possible explanations for the observed differences in childhood obesity prevalence among the study neighborhoods range from sociodemographic characteristics of the populations enrolled in WIC to differences in implementation of population-wide obesity prevention policies. In this study, racial/ethnic composition and income-to-poverty ratio were used to assess changes in the sociodemographic characteristics of the study neighborhoods. If the observed declines in 3-year obesity prevalence were largely explained by changes in the racial/ethnic composition of the study neighborhoods, it would be reasonable to expect that proportions of Hispanic and non-Hispanic black children, who are known to be at higher risk for obesity than non-Hispanic white children in the United States, would be significantly lower in 2010 than in 2004. However, a careful review of the racial/ethnic composition data shows that the proportions of these 2 high-risk groups remained fairly stable from 2004 to 2010 across all study neighborhoods. Furthermore, in 2010 WIC-enrolled children in each borough were living with families in greater poverty than were the WIC-enrolled children in 2004 as evidenced by the average decrease in income-to-poverty ratio in each borough. This finding suggests that the observed differences in changes in obesity prevalence cannot be attributed to the changing racial/ethnic or socioeconomic composition of the neighborhoods.
In light of the numerous interventions implemented in New York City during the last decade to address the growing childhood obesity epidemic, including the implementation of child care regulations in Article 47 of the New York City Health Code in 2007, the results of this study suggest that citywide policies may be working in concert with state and local initiatives to change the food and physical activity environments for low-income, preschool children. Because data for this study came from WIC-enrolled, low-income children, the observed geographic variation in childhood obesity prevalence trends also raises the possibility that families with WIC-enrolled children are better able to adopt and maintain some healthy lifestyles promoted by the WIC program, such as healthy eating, physical activity, and reduced screen time in some neighborhoods than in others.
This study examined childhood obesity prevalence trends at a sub-city level over time. Previous studies of preschool-aged children compared trends at the state or city level but not at the neighborhood level. The use of 3-year prevalence proportions instead of annual prevalence proportions ensured that comparisons were made by using more stable numerators (ie, counts of WIC-enrolled obese 3- and 4-year old children) and denominators (ie, counts of all 3- and 4-year-old children enrolled in WIC) across all study neighborhoods during the 2004–2006 and 2008–2010.
Our study has several limitations. Like all ecologic study designs, the findings of this hypothesis-generating study cannot be used to draw causal inferences at the individual level. Second, we had no information on the national origin or length of time in the United States of WIC participants; therefore, it was not possible to assess whether changes in the makeup of racial/ethnic subpopulations contributed to changes in obesity prevalence across the study areas. Furthermore, we cannot rule out the effect of more children who are not at risk of obesity enrolling in WIC as a result of the economic downturn that occurred in New York City and nationwide during 2008–2010. Finally, the scope and reach of health promotion activities in DPHO areas are known to have expanded during the study period; however, we were not able to assess the extent to which this expansion may vary across the DPHO areas or may explain the observed neighborhood disparities in childhood obesity prevalence trends.
Although work still remains to eliminate these health disparities (particularly in the South Bronx where obesity prevalence during both 2004–2006 and 2008–2010 was approximately twice the Healthy People 2020 target of 9.6% for early childhood), evidence of declines in childhood obesity among children enrolled in WIC in all study areas and a narrowing of the gap between high-risk and low-risk neighborhoods in Manhattan and the Bronx is encouraging. New York State and New York City have been proactive and innovative in childhood obesity prevention with statewide and citywide initiatives focused on improving age-appropriate physical activity and access to affordable healthy foods in early child care and WIC settings. Future research should include measures of the built environment and individual exposure to known interventions and policies to prevent childhood obesity, including exposure to child care, and should incorporate multilevel regression modeling to fully understand factors associated with childhood obesity prevalence trends in New York City neighborhoods.