Post on 13-Dec-2015
description
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