Urbanization and Health
CitationLi, Linyan. 2017. Urbanization and Health. Doctoral dissertation, Harvard T.H. Chan School of Public Health.
AbstractThere has been rapid urbanization in China, the largest developing country in the world, which brings major changes to people’s lives. In addition to the change of socioeconomic status, most people also experience dramatic shifts in lifestyles and the residential environment. On one hand, people have more access to better resources, including healthcare, education, job opportunities, etc. In the meantime, however, the prevalence of some “Western symptoms”, including obesity and asthma, has been on the rise over the past few decades. Since the pace of urbanization is still fast and is likely to last, it is a critical time point to identify the factors that are connected to these diseases, which can provide evidence for individuals, companies and policy makers to make informed decisions in the future. Among the large number of factors that possibly affect people’s health, in this thesis we prioritize and discuss about three of them which are closely related to urbanization, and on which people make effective changes to avoid or reduce the negative impact.
The first aim is to study the association between migration status and respiratory symptoms. With the rapid urbanization in China, significant migration from rural to urban areas and between urban areas has been observed, and the difference from local urban population in lifestyles has not been filled yet. The migration trend is accompanied by a significant increase in the prevalence of asthma. In this aim, we contrast the health conditions between domestically migrating population and long-term residents and their children with a focus on asthma and allergic symptoms. It is found that children from migrant families have lower prevalence of asthma and other respiratory disease compared to the local families within our study population.
The finding of the first aim led us to explore further on the early life exposure factors. In aim 2, we investigated the effect of cesarean section (C-section) on childhood asthma and obesity. The C-section rate has increased dramatically in the past 20 years. With more access to better healthcare facilities, more mothers choose delivery by C-section without medical necessity. While many studies have focused on the increased cost burden for the healthcare system, there is insufficient attention on the possible health consequences of elevated C-section rate. Our results indicated that C-section is a strong and consistent risk factor for developing asthma and allergic symptoms, as well as being overweight and obese.
For the third aim, a different angle is taken to explore the effect of neighborhood greenness and asthma/allergic diseases. Although green spaces are built with the intention of promoting physical activity and creating recreational facilities, there exists mixed evidence on how greenness is associated with respiratory health. We conducted a comprehensive evaluation of residential greenness by using different measures of greenness, including the normalized difference vegetation index (NDVI) and distance to the closest park. Different measures yielded different results, which suggests more information needs to be collected on the specific type of greenness in order to tackle this complexity.
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