107 / 2019-10-31 04:16:30

Easy access to subway stations and obesity: Evidence after subway boom in China

Overweight and obesity, subway station, propensity score, difference-in-difference model, China

Introduction
The correlation between convenient access to subway stations and reduced obesity has been established in developed countries. However, the causal nature of this relationship still cannot be established; subway construction in developed countries is so saturated that studies cannot obtain data that includes a shift in exposure to subway stations. Nowadays, the dramatic subway boom in developing countries gives us a chance to address this concern. This study applies an analysis strategy with repeated cross-sectional data about migrant people in Chengdu, China, to fill the gap in the existing literature.
Method
The body mass index (BMI) data come from a repeated cross-sectional study concerning health-related issues of migrant workers in Chengdu, China. The first survey was conducted in 2008 when no subway system existed in this city, and the second survey was conducted in 2018 after a mature subway system had been built. Respectively, 1,015 and 1,797 individuals were recruited. The analysis strategy using the propensity score in the different-in-different model (DID) was used in this study.
Results
The respondents’ mean BMI increased by about 1.0 kg/m2 over the ten years. However, compared with people who live outside the 400 m subway station buffer zones, people who live inside the buffer zones have a significantly reduced BMI increase of 0.545 kg/m2, after adjusting for other related factors. The results for those living inside the 800 m subway station buffer zones are similar to those for the 400 m setting.
Conclusions
This study provides the latest evidence about the effect of subway construction on reducing obesity. The results will help policymakers decide where to build subway stations from a public health perspective.