PH200 Module 3, Unit 3: Epidemiology

Introduction to Epidemiology

• Definition: Study of distribution and determinants of disease frequency in human populations.
• Key Terms:
  • Disease: Defined as a health outcome; not always clear-cut (e.g., diarrhea from various infectious agents).
  • Disease Frequency: Number of individuals with a disease/health outcome vs. those without.
    • Incidence: Rate of new cases over time.
    • Prevalence: Total number of cases at a specific time.
  • Distribution: Focuses on who, when, and where regarding health outcomes.
  • Determinants: Evaluates relationships within data categorized by who, when, and where.
  • Human Population: Epidemiologists often use observational methods, studying human populations.

Study Types in Epidemiology

• Observational vs. Experimental: Epidemiology often uses observational studies over experimental.

1. Intervention Studies

• Purpose: Test new treatments (e.g., drugs, vaccines).
• Methodology:
  • Often involve randomized double-blinded trials to eliminate bias.
  • Clinical trials required for new treatment approvals.

2. Cohort Studies

• Objective: Link exposure to results through observation.
• Characteristics:
  • Large, normal population exposed to a risk factor.
  • Follow population over time to measure disease development.
  • Relative Risk: Measures association strength between risk factor and health outcome.

3. Case-Control Studies

• Objective: Start with ill individuals and look retrospectively at risk factor exposure.
• Characteristics:
  • Efficient with smaller populations than cohort studies.
  • Match cases (ill individuals) with controls (healthy individuals) based on factors like age, sex.
  • Odds Ratio: Estimate of relative risk, comparing exposure ratios in case vs. control groups.

Examples

• Smoking and Lung Cancer: Historical example illustrating who and when questions to establish determinants.

Conclusion

• Types of studies: Intervention, cohort, and case-control.
• Next module will discuss bias in studies.