What are possible reasons locations in epidemiological research have not been incorporated as much as other components in epidemiological research? How can spatial epidemiology be considered as an interdisciplinary science?
As mentioned in the paper, I think two of the major reasons is the availability of data and the appearance of easy-to-use GIS systems.
First, there is limited high-quality geographic data, which makes it difficult to conduct GIS analysis. I speak of this from personal experience since I have used GIS before, and when conducting analysis in rural areas or middle east countries, I often struggle to find shapefiles and a complete region code database. Many countries also lack data on disease and residence of individuals. For example, one of the papers mentioned that not all countries have a cancer registry, which becomes a barrier to conducting ecological studies. Moreover, we only started adopting electronic health records in the last few decades. Before that, most data is only available in paper form, meaning there is substantial difficulty in retrieving data and conducting statistical analysis using computers.
Second, GIS systems that are easy to use have only emerged relatively recently. I have tried using GIS and they are powerful tools for analysis. They have statistical packages integrated and could handle complex what-if questions with lots of conditionals. With the right data, I could get my answer in a few clicks. However, I imagine a few decades ago, GIS system may have been a lot more difficult to use. Statistical packages may not have been available, requiring researchers to write their own codes from scratch. The need for so much manual labour may have barred researchers from conducting spatial research, as compared to other quantitative and statistical analysis which could be done easily on spreadsheets like Excel.
Spatial Epidemiology could be considered as an integrated science since it incorporates the ideas and principles of lots of discipline. The fundamental usage of spatial epidemiology was rooted in public health when John Snow mapped cholera cases in London, finding links of disease with water. Spatial epidemiology uses statistical methods such as Bayesian analysis and Moran’s I for spatial autocorrelation. It uses the tools of GIS from geography, studying the relationship between people and the environment. It also uses the idea of environmental science and social science, since it considers pollution and socioeconomic status as risk factors and determinants of disease.
Explain why it is widely recognized that the place where an individual lives or works should be considered as a potential disease determinant and give some examples?
It is because environmental factors could be important risk factors to a disease. Example given in the papers were the high incidence of hepatoma in Asia found to be linked to hepatitis B, higher risks of cancer when working in the furniture industry, risk of cancers when living close to an overhead power line, et cetera. These risks are often unknown or undiscovered until the relevant investigation is done. These studies may not reveal a definite causal relation, but they answer important public health questions, such that the public will know whether they have increased risk for a certain disease when they are exposed to a specific thing. I could think of a few more examples from where I live. For example, miners and construction workers in China show a much higher prevalence of COPD and lung cancer. This is because they are constantly exposed to ash, dust, and asbestos in their work environment. In Hong Kong, a building had a serious outbreak of SARS in 2003. When investigating why the virus spread so quickly, researchers found that this is due to the building design, where virus particles could travel easily from floor to floor in the central air vent. These examples get to show that our working and living environment could drastically influence our health and disease.