Environments Impact on Childrens Diet, Activity & Obesity: A Natural Experiment

儿童肥胖症是美国最突出的公共卫生问题之一，专家认为，环境和政策变化可能是解决这一流行病的重要组成部分。但有关环境的文献大多是横截面的，缺乏随机分配，因此专家们呼吁采用准实验方法，特别是自然实验，以产生为政策提供信息所必需的因果估计。我们提出的研究利用了一个这样的自然实验，即军人子女搬迁到新的学校和社区，因为他们的军人父母的转移。这种重新安置，或永久性改变站（PCS），通常每2-3年发生一次，由军方决定，以支持独特的任务和单位。就我们的目的而言，PCS移动意味着军事人员在任何给定时间点的位置及其位置随时间的变化在很大程度上与家庭成员的饮食和活动行为无关。因此，他们的孩子可以说是外源性的“分配”到学校和社区的食物和体育活动（以下简称FPA）的环境。 我们建议收集和分析纵向数据样本的中学生从军事家庭的FPA环境中产生的PCS移动对他们的肥胖和相关行为的影响，可以说是外源性的变化。本研究的具体目标如下：1.描述样本军人子弟学习和生活的学校和社区的FPA环境。2.检查横截面盟友是否学校和邻里FPA环境的军人子女与饮食，体育活动，久坐不动的行为，和身体成分。3.分析PCS移动导致的FPA环境变化如何影响同一个孩子纵向的饮食、身体活动、久坐行为和身体成分的变化。 我们的研究将对FPA环境对儿童健康行为和结果影响的文献做出重大贡献。准实验设计和纵向分析解决了人们对自我选择的共同关注，这种关注具有有限的因果推理。我们还将收集平民儿童样本的基线数据，与我们的军事样本进行比较，并使用倾向评分加权法得出可推广的估计。我们提出的研究在其他方面也是创新的。例如，我们提供了一个关于环境如何影响能量平衡和身体成分的更完整的图片，而不仅仅是关注饮食或体育活动。此外，我们关注的是青少年时期，当时建筑环境的影响可能是身体活动和饮食的一个强有力的决定因素。最后，关注军队士兵的孩子是有用的，因为这些家庭更有可能来自种族/少数民族群体，他们肥胖的风险更大，但在以前的研究中没有很好的代表性。

DESCRIPTION (provided by applicant): Childhood obesity is one of the most prominent public health concerns in the U.S. Experts believe that environmental and policy changes will likely be essential components of efforts to address this epidemic. But the literature on the environment is largely cross-sectional and lacks random assignment, so experts have called for quasi-experimental methods, particularly natural experiments, to produce the causal estimates necessary to inform policy. Our proposed study leverages one such natural experiment where military children relocate to new schools and neighborhoods as a result of their military parents' transfers. Such relocations, or Permanent Change of Station (PCS), typically occur every 2-3 years and are determined by the military to support the unique missions and units. For our purposes, PCS moves imply that the locations of military personnel at any given point in time and the changes in their locations over time are largely unrelated to family members' diet and activity behaviors. Consequently, their children are arguably exogenously "assigned" to school and neighborhood food and physical activity (hereafter, FPA) environments. We propose to collect and analyze longitudinal data on a sample of middle school children from military families to examine the effects of arguably exogenous changes in FPA environments resulting from PCS moves on their obesity and related behaviors. Our specific aims are as follows: 1.Describe the FPA environments in the schools and neighborhoods where our sample military children study and live. 2.Examine cross-section ally whether school and neighborhood FPA environments of military children are associated with diet, physical activity, sedentary behavior, and body composition. 3.Analyze how changes in FPA environments resulting from PCS moves influence changes in diet, physical activity, sedentary behavior, and body composition for the same child longitudinally. Our study will make a significant contribution to the literature on the effects of FPA environment on children's health behaviors and outcomes. The quasi-experimental design and longitudinal analyses address common concerns about self-selection that have limited causal inference. We will also collect baseline data on a sample of civilian children to compare to our military sample and produce generalizable estimates using propensity score weighting. Our proposed study is also innovative in other ways. For example, we provide a more complete picture of how the environment influences energy balance and body composition instead of focusing on just diet or physical activity. Moreover, we focus on adolescence, when the impact of the built environment may be a strong determinant of physical activity and diet. Finally, the focus on children of Army enlistees is useful because these families are more likely to be from racial/ethnic minority groups, for whom the risk of obesity is greater, but not well-represented in previous studies.