Overview of Environmental Epidemiology: Part IV

Arindam BasuPrepared for HLTH214

School of Health SciencesUniversity of Canterbury

July 20, 2015

Epidemiological Study Designs

I Discuss the environmental epidemiological study designs

I Ecological

I Case Series or Surveillance

I Cross Sectional

I Case Control

I Cohort

Ecological

I Refers to exposure and outcomes both data in aggregate form

I Usually linear models or other forms of modelling

I Examples: Air Pollution and Cardiovascular disease, or Air Pollution and Asthma

I Studies can also be in the form of cluster analysis

I A major limitation is ecological fallacy

Case series (surveillance)

I Very important for Environmental Health Surveillance

I Systematic, ongoing, data collection, analysis, and dissemination efforts

I For identification of clusters or for hypothesis generation

Cross sectional study

I Exposure and Outcome Data are collected at the same time

I Cannot deduce causal association

I Ideal study design for prevalence estimation

I Usually in the form of surveys

Case control

I Cases with health outcome and controls without health outcomes

I Sampled on the basis of outcomes

I Exposure is ascertained usually retrospective in the form of likelihood of exposure

I Ideal for rare disease investigation, such as cancer

Cohort

I Sampling conducted on the basis of exposure

I People are followed up in time

I People who are sampled for exposure (cohorts) must be disease free in thebeginning

I Relative Risk estimates are effect size estimates

Conclusion

I This was an overview of epidemiology

I Environmental Epidemiology will have Environmental Exposures

I Ecological studies, Surveillance, and Case Control studies are widely used

I For occupational epidemiology, retrospective cohort studies are widely used