Epidemiology
Epidemiology - It is the study of the distribution and determinants of health related states or events in
specific populations and the application of this study to control health problems.
Two assumptions inherent in epi studies - 1. Diseases are NOT randomly distributed in populations.
2. Diseases have specific causes that can be identified, prevented, and treated.
Functions of Epidemiology - - To discover the agent, host, and environmental factors which affect
health, in order to provide the scientific basis for the prevention of disease and injury and the promotion
of health.
- To determine the relative importance of causes of illness, disability, and death, in order to establish
priorities for research and action.
- To identify those sections of the population which have the greatest risk from specific causes of ill
health, in order that the indicated action may be directed appropriately.
- To evaluate the effectiveness of health programs and services in improving the health of the
population.
Objectives of Epidemiology - 1. To identify the etiology (cause) of a disease and the risk factors
associated with the disease.
2. To determine the extent of disease found in the community. What is the burden of disease?
3. To study the natural history and prognosis of the disease
4. To evaluate both existing and new preventative and therapeutic measures and modes of health care
delivery
5. To provide the foundation for developing public policy and regulatory decisions relating to
epidemiologic problems
Issues in Epidemiology - -Where there is a link between factor and health outcome - does this mean the
factor is the cause of disease?
-Is there is an association, does the amount of disease vary according to the amount of exposure to the
factor?
,-Based on the observation of such an association, what practical steps should individuals and public
health departments take?
-Do the findings from an epidemiologic study merit panic or measured response?
-How applicable are the findings to settings other than the one in which the research was conducted?
Epidemiological Approach - -Observation
-Definition of disease process
-Descriptive epidemiology
-Analytical Epidemiology
-Experimental Epidemiology
Surveillance - Ongoing and systematic collection, analysis and interpretation of health related data
-Assess public health status, define public health problems, evaluate programs, stimulate research
Primary prevention - prevention or cessation of risk factor exposure (active or passive)
Secondary prevention - intent to reduce progress of disease, screenings for "high risk" subjects -
detection. Involves people who already have a disease.
Tertiary prevention - reduces limitation of disability from disease.
Population-based approach/public health approach: - -Applied to whole population, dietary
modification, must be inexpensive and non-invasive
High-risk approach (clinically based): - -Expensive or invasive (ie. colonscopy for those with family
history, cholesterol screening for children from high risk families)
Hippocrates - 400 BC - Found that disease is associated with physical environment
Francis Bacon - Inductive logic, Law of Mortality --> law of epidemics.
, Royal Society of London - 1662 - John Graunt published a comparative study of mortality and morbidity
in human populations. Referred to as the Columbus of Statistics. Quantified patterns of disease.
James Lind - 1747 - etiology and treatment of scurvy, use of comparison group.
-Noticed high morbidity rate among sailors
-Noticed diet among sailors at sea hard on digestion
-Conducted experimental trial using comparison group
Edward Jenner - 1768 - use of observational data
Pierre Charles-Alexandre Louis - comparison of groups of individuals, emphasized use of statistical
methods in medicine
William Farr - Mortality surveillance, use of vital statistics,
-In charge of medical statistics in the Office of the Registrar General for England (1839)
-Set up a system for routine compilation of the numbers and causes of deaths
-Addressed many issues relevant to modern epidemiology including case definition, using comparison
populations, and addressing confounding factors such as age.
John Snow - - "Father of Epidemiology"
-Investigated cholera 1849-1854
-Lambeth company - water above London
-Southward and Vauzhall Company - water below London
-1854 epidemic of cholera in London
-Tested hypothesis
-Charted frequency and distribution of disease
-Ascertained cause/determinant
-First to draw all three components of epidemiology together
oDistribution, determinants, population
Epidemiology - It is the study of the distribution and determinants of health related states or events in
specific populations and the application of this study to control health problems.
Two assumptions inherent in epi studies - 1. Diseases are NOT randomly distributed in populations.
2. Diseases have specific causes that can be identified, prevented, and treated.
Functions of Epidemiology - - To discover the agent, host, and environmental factors which affect
health, in order to provide the scientific basis for the prevention of disease and injury and the promotion
of health.
- To determine the relative importance of causes of illness, disability, and death, in order to establish
priorities for research and action.
- To identify those sections of the population which have the greatest risk from specific causes of ill
health, in order that the indicated action may be directed appropriately.
- To evaluate the effectiveness of health programs and services in improving the health of the
population.
Objectives of Epidemiology - 1. To identify the etiology (cause) of a disease and the risk factors
associated with the disease.
2. To determine the extent of disease found in the community. What is the burden of disease?
3. To study the natural history and prognosis of the disease
4. To evaluate both existing and new preventative and therapeutic measures and modes of health care
delivery
5. To provide the foundation for developing public policy and regulatory decisions relating to
epidemiologic problems
Issues in Epidemiology - -Where there is a link between factor and health outcome - does this mean the
factor is the cause of disease?
-Is there is an association, does the amount of disease vary according to the amount of exposure to the
factor?
,-Based on the observation of such an association, what practical steps should individuals and public
health departments take?
-Do the findings from an epidemiologic study merit panic or measured response?
-How applicable are the findings to settings other than the one in which the research was conducted?
Epidemiological Approach - -Observation
-Definition of disease process
-Descriptive epidemiology
-Analytical Epidemiology
-Experimental Epidemiology
Surveillance - Ongoing and systematic collection, analysis and interpretation of health related data
-Assess public health status, define public health problems, evaluate programs, stimulate research
Primary prevention - prevention or cessation of risk factor exposure (active or passive)
Secondary prevention - intent to reduce progress of disease, screenings for "high risk" subjects -
detection. Involves people who already have a disease.
Tertiary prevention - reduces limitation of disability from disease.
Population-based approach/public health approach: - -Applied to whole population, dietary
modification, must be inexpensive and non-invasive
High-risk approach (clinically based): - -Expensive or invasive (ie. colonscopy for those with family
history, cholesterol screening for children from high risk families)
Hippocrates - 400 BC - Found that disease is associated with physical environment
Francis Bacon - Inductive logic, Law of Mortality --> law of epidemics.
, Royal Society of London - 1662 - John Graunt published a comparative study of mortality and morbidity
in human populations. Referred to as the Columbus of Statistics. Quantified patterns of disease.
James Lind - 1747 - etiology and treatment of scurvy, use of comparison group.
-Noticed high morbidity rate among sailors
-Noticed diet among sailors at sea hard on digestion
-Conducted experimental trial using comparison group
Edward Jenner - 1768 - use of observational data
Pierre Charles-Alexandre Louis - comparison of groups of individuals, emphasized use of statistical
methods in medicine
William Farr - Mortality surveillance, use of vital statistics,
-In charge of medical statistics in the Office of the Registrar General for England (1839)
-Set up a system for routine compilation of the numbers and causes of deaths
-Addressed many issues relevant to modern epidemiology including case definition, using comparison
populations, and addressing confounding factors such as age.
John Snow - - "Father of Epidemiology"
-Investigated cholera 1849-1854
-Lambeth company - water above London
-Southward and Vauzhall Company - water below London
-1854 epidemic of cholera in London
-Tested hypothesis
-Charted frequency and distribution of disease
-Ascertained cause/determinant
-First to draw all three components of epidemiology together
oDistribution, determinants, population
