Course contents of Epidemiology

Unit 1: Introduction to Epidemiology

Unit 2: Theories of Disease Causation

Unit 3: Natural history of disease and levels of prevention

Unit 4: Infectious disease cycle

Unit 5: Basic measurements in epidemiology

Unit 6:  Descriptive study design

Unit 7:  Analytic study design

Unit 8: Measures of strength of association

Unit 9: Analysis of cause effect relationship

Unit 10: Screening in disease control

Unit 11: Public health surveillance

Unit 12: Investigation of epidemics

Introduction to Epidemiology

Definition of Epidemiology

Simple old definitions

Oxford English Dictionary

• • Epidemiology is the branch of medical science that treats epidemics.

American Journal of Epidemiology, Kuller LH.

• • Epidemiology is the study of epidemics and their prevention.

Modern Epidemiology, Anderson G. In: Rothman KJ.

• • Epidemiology studies about the occurrence of illness. 

Modern Definition of Epidemiology

§ The word epidemiology comes from the Greek words: Epi = on or upon, Demos = people, and logos = the study of.

§ Epidemiology is the science of discovering the causes of illness and injury in populations.

§ Many definitions have been proposed, but the following definition captures the underlying principles and the public health spirit of epidemiology:

§ Epidemiology is the study of the distribution and determinants of health-related states and events in populations, and the application of this study to control health problems.

The latest definition:

Epidemiology is the study of the frequency, distribution and determinants of disease and other health related states or events in specified population and the application of this study to the promotion of health and prevention and control of health problems.

• • This definition  includes several terms which reflect some of the important principles of the discipline.

Ø Study:

• • Epidemiology is a scientific discipline, sometimes called “the basic science of public health.”

• • It has, at its foundation, sound methods of scientific inquiry.

Ø Distribution:

• • Epidemiology is concerned with the frequency and pattern of health events in a population/how many cases occur over a given time period.

• • Frequency includes not only the number of such events in a population, but also the rate or risk of disease in the population.

• • The rate (number of events divided by size of the population) is critical to epidemiologists because it allows valid comparisons across different populations.

Ø Determinants:

• • are factors or events that are capable of bringing about a change in health.

• • Examples of determinants

• • Biologic agents- bacteria

• • Chemical agents- carcinogens

• • Less specific factors- stress, drinking, sedentary lifestyle, or high-fat diet

ü The part of epidemiology dealing with the causes and determinants of diseases is Analytical Epidemiology.

Diseases and other health related conditions/events:

• • It indicates as the vast area is covered by epidemiology.

• • Some examples of health related conditions are:
    
    • • Injuries
    • • Vital events:
        
        • • Birth
        • • Death
        • • Marriages and
        • • Divorce

    • • Health related behaviors:
        
        • • Sexual behavior
        • • Smoking,
        • • Alcoholism
        • • Drug abuse

    • • Social factors: poverty

§ Pattern:

Epidemiologists describe disease/states in terms of

• • time,

• • place

• • and personal  characteristics.

Distribution:

• • Epidemiology describes health events

• • It asks the questions:  
    
    • • What?
    • • When?
    • • Where?
    • • Who?.

• • This part or branch of epidemiology is Descriptive Epidemiology.

Ø Specified populations:

• • Even though epidemiologists and physicians in clinical practice are both concerned with disease & the control of disease, they differ greatly in how they view the patient.

Ø Application:

• • Epidemiology is more than “the study of.”

• • As a discipline within public health, epidemiology provides data for directing public health action.

Two Approaches of Studying Epidemiology

1. 1. Descriptive  Epidemiology:

• • It describes health problems in terms of PPT (person, place, and time).

2. Analytic Epidemiology:

• • It identifies causative and protective factors for diseases and health related conditions by testing the proposed hypothesis.