introduction to epidemiology

Etymology of "Epidemiology"

Epi (upon), Demos (people), Logos (study).

Definition of Epidemiology (1873)

The branch of medical science which treats epidemics.

Definition of Epidemiology (1927)

The science of the mass phenomena of infectious diseases.

Definition of Epidemiology (1934)

The study of disease, any disease, as a mass phenomenon.

Definition of Epidemiology (1960)

The study of the distribution and determinants of disease frequency in man.

Definition of Epidemiology (1988)

The study of distribution/determinants of health states in specified populations and its application to control.

Anatomy of Definition: "Study"

Based on principles of Statistics and research methodology.

Anatomy of Definition: "Distribution"

Triad of Time, Place, and Person (When, Where, Who).

Anatomy of Definition: "Determinants"

Causes or risk factors (How and Why).

Anatomy of Definition: "Health-related states"

The whole spectrum of health status.

Anatomy of Definition: "Population"

Focuses on whole groups rather than individuals.

Cornerstone of Preventive Medicine

Epidemiology.

Original Scope of Epidemiology

Limited to epidemics of acute infectious diseases.

Modern Scopes of Epidemiology (Examples)

Chronic, Clinical, Serological, Cancer, Malaria, Genetic, and Molecular epidemiology.

Three Components of Epidemiology

Disease frequency, Distribution, and Determinants.

Primary tool of Epidemiology

Biostatistics.

Basic measures of disease frequency

Rates and ratios (e.g., prevalence, incidence, death rates).

Purpose of rates in Epidemiology

To compare disease frequency between different populations or subgroups.

Key tenet of disease distribution

Disease does not occur randomly, but in patterns reflecting underlying factors.

Goal of Descriptive Epidemiology

To study distribution patterns by time, place, and person to generate hypotheses.

Goal of Analytical Epidemiology

To test hypotheses and identify underlying causes or risk factors.

Sequence of Epidemiological Study

Descriptive (Generate) -> Analytic (Test) -> Experimental (Confirm) -> Control.

Ultimate Goal of Epidemiology

To eliminate/reduce health problems and promote societal well-being.

Epidemiology in Health Management

Community diagnosis, planning/evaluation of services, and policy development.

Epidemiology in Public Health Practice

Outbreak investigation, surveillance, and determining transmission modes.

Epidemiology in Clinical Practice

Assessing effectiveness of treatments, diagnostic tools, and prognosis.

Unit of Study: Epidemiology vs. Clinical

Epidemiology (Population) vs. Clinical (Individual cases).

Objective: Epidemiology vs. Clinical

Epidemiology (Identify source/mode) vs. Clinical (Cure the patient).

Examination: Epidemiology vs. Clinical

Epidemiology (Community survey) vs. Clinical (Individual patient).

Concern: Epidemiology vs. Clinical

Epidemiology (Sick and Healthy) vs. Clinical (Sick only).

Concept: Epidemiology vs. Clinical

Epidemiology (Bio-statistical) vs. Clinical (Bio-medical).

Outcome: Epidemiology vs. Clinical

Epidemiology (Planning/Promotion) vs. Clinical (Cure, disable, or death).

Required knowledge for an Epidemiologist

Public health, Clinical medicine, Pathophysiology, Statistics, and Social sciences.

The Epidemiological Approach

Based on asking questions, getting answers, and making comparisons.

"Health Event" Questions

What is the event? Magnitude? Where? When? Who? Why?.

"Health Action" Questions

What can be done? Prevention? Resources needed? Difficulties?.

Case-control Comparison

Compares a group with the disease to a group without it to find host/environmental differences.

Cohort Comparison

Compares a group exposed to a risk factor to a group not exposed.

Descriptive vs. Analytic Questions

Descriptive (Who, Where, When) vs. Analytic (How, Why).