Types of Epidemiological Studies
Cohort (prospective) - direct estimate of risk
- Presence of exposure determined in sample of population
- Entire sample followed and incidence of disease compared for those with and without the exposure
Case control (retrospective) - indirect estimate of risk
- Sample selected based on presence or absence of disease
- Proportion of cases with history of exposure before onset of disease compared with controls
Cross-sectional or prevalence - associations
- Presence of disease determined in sample of population
- Proportion of cases with history of exposure compared with non-cases
- Prevalence of disease compared for those with and without the exposure
- Temporal sequence of exposure relative to disease unknown
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