21. Ecological studies. Immigrant studies

From greek.doctor
  • Ecological study
    • Also called a correlational study
    • A study which aims to identify a correlation between a risk factor or protective factor and a disease
    • Use data which is already collected, from
      • Census data
      • Registries
      • Etc.
    • Doesn’t use data based on individual cases
    • Uses data based on the whole population, like disease prevalence, incidence, mortality
    • Focuses on specific problems, like within a region or population
    • Advantages
      • Inexpensive
      • Easy to carry out
    • Disadvantages
      • Prone to bias and confounding
    • Example:
      • Comparing the prevalence of a disease in different regions
      • Finding the association between suicide rate and proportion of Protestant religion in different Prussian provinces
  • The ecological fallacy
    • = incorrectly assuming that an association seen at a populational level also reflects association at an individual level
    • Example
      • There is good correlation between salt intake and hypertension when comparing different countries
      • However, correlation on an individual level is difficult to demonstrate
  • Immigrant studies
    • Compares immigrants to other populations, allowing the evaluation of the effect of the environment while the genetic background remains the same
    • Compares disease incidence between:
      • A group of migrants to a new country
      • Ethically similar people in their native country
      • The native population of the new country
    • Example
      • Cancer rates among Japanese immigrants in the US approached the US cancer rate after 2 generations