1.1.Introduction to Epidemiology.ppt

EPI 810: Introduction To
Epidemiology
Nigel Paneth
Lecture 810 1.1

Syllabus: Time, Place, and
Person
 Time: Mondays and Wednesdays
4:10-5:20 p.m.
 Office hours: BY ARRANGEMENT
 Place: Room A -131 East Fee Hall
–Department of Epidemiology
classroom.
 Person: Nigel Paneth, Instructor.
• 353-8623; paneth@msu.edu

READINGS
 Required Texts:
1) Leon Gordis: Epidemiology. 3rd edition,
2004
2) Articles: In Department of Epidemiology
library, labeled as EPI 810 Articles
 Highly recommended Texts
1) Last J M, A Dictionary of Epidemiology,
4th edition 2001
2) Chin J: Control of Communicable
Disease Manual, 17th edition (required for
EPI 817)

EVALUATION
 Two tests (in classroom)
– Midterm (15% )
– Final exam (30%)
 Class participation (15%)
 Term paper (40%)
 No assigned exercises but be prepared to go
over exercises at back of chapters in class

IMPORTANT DATES
 NO CLASSES ON
– MON Sept 6 (Labor day)
– WED Nov 24 (Thanksgiving eve)
 INSTRUCTOR AWAY WEEK OF NOVEMBER 1
– MON Nov 1 - Mid-term
– WED Nov 3 - Special session on searching public
health databases
 OPTIONAL REVIEW SESSION MON Dec 6
 FINAL EXAM THUR Dec 16 5:45

DUE DATES FOR
COMPONENTS OF PAPER
1. TOPIC MON 9/20
2. 10 ITEM BIBLIOGRAPHY WED 9/29
3. ONE PAGE OUTLINE MON 10/18
4. FIRST DRAFT WED 11/10
5. FINAL DRAFT MON 12/6

DRAFT COMMENTS
 MINOR REVISIONS - About a 3.5 in its
present state, can get up to around 4.0
with modest effort
 SOME REVISION - About a 3.0 in its
present state, needs more work to get a
grade near or at 4.0
 MAJOR/MUCH REVISION – Only at about
2.5 now – really needs work to get up to
good grade. Consider meeting with me

Two Definitions of an Epidemic
Last JM: A Dictionary of Epidemiology. 4th ed
THE OCCURRENCE IN A COMMUNITY OR REGION OF CASES
OF AN ILLNESS, SPECIFIC HEALTH-RELATED BEHAVIOUR, OR
OTHER HEALTH-RELATED EVENTS CLEARLY IN EXCESS OF
NORMAL EXPECTANCY.
From the Babylonian Talmud (Tractate Taanit, 21A)
A CITY THAT HAS FIFTEEN HUNDRED MILITARY AGE MEN SUCH
AS AKKO, AND THAT SUFFERS NINE DEATHS IN THREE DAYS,
THAT IS CONSIDERED A PLAGUE. A CITY WITH FIVE HUNDRED
SUCH AS AMIKO, AND HAS THREE DEATHS IN THREE DAYS,
THAT IS CONSIDERED A PLAGUE.

Definitions of Epidemiology
Oxford English Dictionary
THE BRANCH OF MEDICAL SCIENCE WHICH TREATS
OF EPIDEMICS
Kuller LH: Am J Epid 1991;134:1051
EPIDEMIOLOGY IS THE STUDY OF "EPIDEMICS"
AND THEIR PREVENTION
Anderson G,quoted in Rothman KJ: Modern
Epidemiology
THE STUDY OF THE OCCURRENCE OF ILLNESS

Definitions of Epidemiology
Lilienfeld A: in Foundations of Epidemiology
THE STUDY OF THE DISTRIBUTION OF A DISEASE OR
A PHYSIOLOGICAL CONDITION IN HUMAN
POPULATIONS AND OF THE FACTORS THAT INFLUENCE
THIS DISTRIBUTION
Last JM: A Dictionary of Epidemiology
THE STUDY OF THE DISTRIBUTION AND
DETERMINANTS OF HEALTH RELATED STATES AND
EVENTS IN POPULATIONS AND THE APPLICATION OF
THIS STUDY TO CONTROL OF HEALTH PROBLEMS“

What Is The Unique Skill
Of Epidemiologists?
MEASURING
DISEASE
FREQUENCY IN
POPULATIONS

Measuring Disease Frequency
Has Several Components
 Classifying and
categorizing disease
 Deciding what
constitutes a case of
disease in a study

 Finding a source for
ascertaining the cases
 Defining the population
at risk of disease
 Defining the period of
time of risk of disease
 Obtaining permission to
study people
 Making measurements of
disease frequency
 Relating cases to
population and time at
risk

Two Broad Types of
Epidemiology
Examining the distribution of a
disease in a population, and
observing the basic features of its
distribution in terms of time,
place, and person.
Typical study design:
community health survey
(approximate synonyms - cross-
sectional study, descriptive
study)
Testing a specific hypothesis
about the relationship of a
disease to a putative cause, by
conducting an epidemiologic
study that relates the
exposure of interest to the
disease of interest.
Typical study designs: cohort,
case-control
DESCRIPTIVE EPIDEMIOLOGY ANALYTIC EPIDEMIOLOGY

The Basic Triad Of
Descriptive Epidemiology
THE THREE ESSENTIAL CHARACTERISTICS
OF DISEASE WE LOOK FOR IN DESCRIPTIVE
EPIDEMIOLOGY:
 TIME
 PLACE
 PERSON

Time
 Changing or stable?
 Seasonal variation.
 Clustered (epidemic) or evenly
distributed (endemic)?
 Point source or propagated.

Place
 Geographically restricted or
widespread (pandemic)?
 Relation to water or food supply.
 Multiple clusters or one?

Person
 Age
 Socio-economic status
 Gender
 Ethnicity/Race
 Behavior

Descriptive Epidemiology Is A
Necessary Antecedent Of
Analytic Epidemiology
To undertake an analytic
epidemiologic study you must first:
 Know where to look
 Know what to control for
 Be able to formulate hypotheses
compatible with laboratory
evidence

A COMMON ERROR IN EPIDEMIOLOGY IS
MOVING TO ANALYTIC EPIDEMIOLOGY
WITHOUT HAVING A SOLID BASE IN THE
DESCRIPTIVE EPIDEMIOLOGY OF THE
CONDITION.
THUS THE FIRST THREE OF
THE FIVE SECTIONS OF THIS
COURSE DEAL WITH
DESCRIPTIVE EPIDEMIOLOGY

The Basic Triad Of
Analytic Epidemiology
THE THREE PHENOMENA ASSESSED IN
ANALYTIC EPIDEMIOLOGY ARE:
HOST
ENVIRONMENT
AGENT

Agents
 Nutrients
 Poisons
 Allergens
 Radiation
 Physical trauma
 Microbes
 Psychological experiences

Host Factors
 Genetic endowment
 Immunologic state
 Age
 Personal behavior

Environment
 Crowding
 Atmosphere
 Modes of communication – phenomena
in the environment that bring host and
agent together, such as:
– Vector
– Vehicle
– Reservoir

Epidemiologists are required to have some
knowledge of the disciplines of public health,
clinical medicine, pathophysiology, statistics, and
the social sciences.
• public health, because of the emphasis on disease prevention.
• clinical medicine, because of the emphasis on disease
classification and diagnosis.
• pathophysiology, because of the need to understand basic
biological mechanisms in disease.
• statistics, because of the need to quantify disease frequency
and its relationships to antecedents.
• social sciences, because of the need to understand the social
context in which disease occurs and presents.

Purposes Of Epidemiology
(Gordis: Epidemiology, p. 3-4)
1. Identify causes and risk factors for
disease.
2. Determine the extent of disease in the
community.
3. Study natural history and prognosis of
disease.
4. Evaluate preventive and therapeutic
measures
5. Provide foundation for public policy

Differences Between
Laboratory Sciences And Field
Sciences
In the Laboratory:
• Mostly experimental
• Variables controlled by the investigator
• All variables known
• Replication easy
• Results valid
• Meaning of results for humans uncertain.
• Little need for statistical manipulation of data.
• Highly equipment intensive

Differences Between
Laboratory Sciences And Field
Sciences
In the Field:
 Mostly observational
 Variables controlled by nature
 Some variables unknown
 Replication difficult; exact replication impossible
 Results often uncertain
 Meaning of results for humans clear
 Statistical control often very important
 Highly labor intensive

Men Women Children Total
1st class 67% 3% 0 38%
2nd class 92% 14% 0 59%
3rd class 84% 54% 66% 62%
Total 82% 26% 48% 62%
EVERY HEALTH OUTCOME HAS SOME
INTERESTING AND USEFUL EPIDEMIOLOGIC
CHARACTERISTIC
DEATH RATES BY SOCIAL CLASS FROM A
CERTAIN CAUSE AMONG 1,316 PEOPLE
WHAT CAUSE OF DEATH IS THIS?

The previous slide shows death
rates by class of ticket on the
Titanic, a large ocean liner that
sank after colliding with an
iceberg in 1912

1.1.Introduction to Epidemiology.ppt

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1.1.Introduction to Epidemiology.ppt