Introduction to Epidemiology

Overview

Epidemiology: Exciting, rapidly growing medical science.
Role: Like medical detectives, collecting data and solving mysteries about disease in populations.
Focus: Differences between descriptive and analytical studies, historical origins, and triumphs.

CDC Definition: Study of distribution and determinants of disease or health status in a population.
Wikipedia Definition: Branch of medicine dealing with incidence, distribution, etc.
Lecture Definition: Science of looking at the health of populations rather than individuals.

John Snow (19th Century, London): Investigated cholera outbreaks using maps and numbers to describe the epidemic. Revolutionary for its time.
- Focused on waterborne diseases and identified the Broad Street pump as a source of cholera.
Before John Snow: Diseases thought to be caused by miasma (fantastical poisonous vapors).
- Advent of microscopes revealed microbes as the cause of diseases.

Clinical Epidemiologists: Use clinical experience and research to make decisions for small groups, often in clinical settings.
Public Health Epidemiologists: Investigate outbreaks, plan vaccine schedules, and manage community health.
Population Epidemiologists: Study large disease trends, risk factors, and incidence/prevalence in populations.
Emerging Types: Collaborate with political science, economics, computer science, and genetics.

Paradigms: How a discipline interacts with the world and understands knowledge, evidence, and truth.
- Ontology: Nature of reality (objective truth vs. imagination).
- Epistemology: How we acquire knowledge (data collection, interrogation, etc.).
- Methodology: Study designs and methods to understand the universe.
Epidemiologic Paradigm: External objective truth accessed via methodologies, measuring risk factors and outcomes.
- Ex: Smoking causes cancer.

Independent vs. Dependent Variables: In epidemiology, an independent variable is an exposure and a dependent variable is an outcome.
- Ex: Smoking (exposure) leads to lung cancer (outcome).
Risk Factor: Exposure that increases/decreases the likelihood of an outcome. Doesn't always need to know the mechanism.
Descriptive Epidemiology: Who, what, where, and when of diseases.
- Example: Prevalence of left-handedness in students (cross-sectional study).

Qualitative vs. Quantitative Studies: Descriptive (qualitative: social sciences) vs. Analytical (quantitative: numbers, statistics).
**Descriptive vs. Analytical Studies:
- Descriptive Studies: Measure and describe single variables (left-handedness example).
- Analytical Studies: Analyze relationships between two or more variables.
- **Observational vs. Experimental Studies:
  - Observational Studies: Case-control, cohort studies; observe without interference.
  - Experimental Studies: Randomized control trials (RCTs), manipulate variables.

Smallpox Eradication: First human disease deliberately eradicated by humans (1980).
- Edward Jenner (Early 1800s): First workable smallpox vaccine.
- Herd Immunity: Protecting unvaccinated individuals by vaccinating a critical proportion of the population.
- Eradication Timeline: Initiated global control in the 1950s, WHU eradication in 1980.

Disease Surveillance: Monitoring diseases with notifiable disease registries (e.g., TB, HIV/AIDS, Ebola).
Diagnostic Tests: Assessing test sensitivity, specificity, and viability for screening tools.
Trend Analysis: Analyzing disease trends to inform public health strategies.
Study Design: Ensuring methodological soundness in research protocols.

Understanding the history and evolution of epidemiology (John Snow's cholera investigation).
Differences between descriptive and analytical studies.
Key roles of different types of epidemiologists in advancing public health.