EPIDEMIOLOGY INTRODUCTION by Dr. Anuj.ppt

1. Dr. Anuj Singh
Asst. Professor
Community Medicine Dept.
UIMS, Prayagraj

5. H I S T O R Y-
 The Greek physician Hippocrates is usually
said to be father of epidemiology. The first
person to have examined the relationship
between occurrence of disease and their
environmental influences; coined the terms
epidemic and endemic.

6. - Dr. John Snow is famous for
the suppression of an 1854
Cholera outbreak in
London’s Golden-square
district.
- He identified the cause of
the out-break as a public
water pump and had the
handle removed, there by
ending the out-break.

7. •FATHER OF MODERN EPIDEMIOLOGY

8. Epidemiology-
Def-
“ The study of the occurrence and distribution of
health related states or events and process in
specified populations, including the study of the
determinants influencing such process, and the
application of this knowledge to the control of
health problems ”
by: John M. Last (1988)

9. Aim of Epidemiology:
The overall aim of epidemiology is to obtain,
interpret and use health information to promote,
protects and restore health; to reduce or remove
diseases; and to advance scientific knowledge to
address the above mentioned purposes.

10. Objective of Epidemiology:
 To undertake “studies” using one of the various
epidemiological methods as observational or
experimental designs undertaken on “health-related
events, states, and processes” including epidemic
outbreaks, diseases, disorders, causes of death,
behaviors, environmental and socioeconomic
processes, effects of preventive programs, and use
of health services

11. Objective of Epidemiology : cont..
 To describe the “distribution,” i.e., the analysis of
facts collected from the “study” according to
person, place, and time
 To work out the “determinants,” such as various
physical, biological, behavioral, and
socioeconomic factors that influence health
 To apply the knowledge gained from the above-
mentioned objectives; to promote, protect, and
restore health; and to advance scientific
knowledge

12. How Epidemiology Can initiate Public Health Action Even
Before the Actual “Cause is Known-
 1768, Edward Jenner showed that variolation can prevent
smallpox
 1747, James Lind showed that lime juice can prevent scurvy
 Mid-nineteenth century, Semmelweis, showed that washing
hands by medical students was protective against
development of puerperal infection among female patients
 1848–1854, John Snow showed that cholera is transmitted by
contaminated water
 Early twentieth century, Goldberger and Fletcher respectively
showed that pellagra and Beri beri were caused by maize
diet and polished rice, respectively
 Mid-twentieth century, Doll and Hill, based on case–control
studies, showed that smoking causes lung cancer

13. Principles of Epidemiology:
6 basic principles of epidemiology is to
define epidemiologic event in terms of-
6Ws-
WHAT?
WHO?
WHEN?
WHERE?
WHY?
So what?

14. Principles of Epidemiology: cont..
What: Define the diseases or health event,
count the cases or health events, and thereafter
divide the no. of cases by an appropriate
denominator to calculate rate

15. Principles of Epidemiology: cont..
Describe the rate so calculated in terms of-
-Who: Person
-When: Time
-Where: Place

16. Principles of Epidemiology: cont..
Why (or how): Compare these rate over
time or for different groups of people and
conclude as to why the rates are different.

17. Principles of Epidemiology: cont..
So what: Apply so conclusion so drawn in
the form of a clinical or public health policy

18. Fundamental concepts
in Epidemiology

19. Five cardinal concepts in epidemiology-
1 Cause, prevention, and treatment of health problem to be
identified
2 Data regarding the causes, prevention, and management of
health problems should be quantified and analyzed
3 Information should be collected from large population
4 Causal association regarding the causes, prevention and
mgmt. of human diseases / health problems can be
ascertained by observational or experimental method
5 Application of epidemiological research should be suitably
used to bring about policy change, whether for public
health or in clinical practice.

20. Five cardinal concepts in epidemiology-
1
Cause, prevention, and treatment of health problem
to be identified-
 Health problems and their prevention can be
achieved by the study of population using
scientific method

21. Five cardinal concepts in epidemiology-
2 Data regarding the causes, prevention, and
management of health problems should be
quantified and analyzed-
Epidemiology is a quantitative science based on
same clinical methods as are used in medical
practice
Additionally, it involves probability, statistics,
socio behavioral sciences and sound research
methods.

22. Five cardinal concepts in epidemiology-
3 Information should be collected from large
population-
Epidemiology focuses on a large group of people
who may be healthy or diseased.

23. Five cardinal concepts in epidemiology-
4 Causal association regarding the causes,
prevention and mgmt. of human diseases / health
problems can be ascertained by observational or
experimental method-
Hypothesis
generation
Hypothesis
testing
Hypothesis
confirmation

24. Five cardinal concepts in epidemiology-
5 Application of epidemiological research should be suitably
used to bring about policy change, whether for public
health or in clinical practice.

25. Clinical medicine Vs Epidemiology
In Clinical Medicine, the unit of
study is a “Case” or “Cases”.
In Epidemiology, the unit of the
study is “Defined population” or
“Population at risk”.
In Clinical Medicine a Physician
is concerned with the individual
patient who is diseased.
The Epidemiologist’s concern are
the disease patterns in the entire
population. (both the sick &
healthy)

26. Clinical medicine Vs Epidemiology
In Clinical Medicine, the Patient
comes to the Doctor.
In Epidemiology, the Investigator
goes out into the community to
find persons who have the diseases
or experience of suspected casual
factors in question.

27.  HOWEVER, CLINICAL MEDICINE & EPIDEMIOLOGY
ARE NOT ANTAGONISTIC.
Most Epidemiological enquiries could never
be established without appropriate clinical
consideration as to how a disease in question
can be identified among the individuals in the
groups under scrutiny.
Likewise, a knowledge of prevalence, etiology
& prognosis derived from the Epidemiological
research is very important to a Clinician for the
diagnosis & management of individual patients.

28. Uses of Epidemiology

29. USES OF EPIDEMIOLOGY

30. Uses of Epidemiology-
1 Healthcare mgmt.
2 Understanding the disease process
3 Public health practice
4 Clinical and individualizes preventive practice

31. Uses of Epidemiology-
1. Making a community diagnosis:
In clinical settings, the clinician makes a clinical
diagnosis.
In health care of a large community, the health
provider must make a “community diagnosis.” By
epidemiological methods to obtain information on the
important health problems and their associated
socio-demographic characteristics, quantifying and
summarizing them.
Once a “community diagnosis” has been made, we
can decide as to which programs would be best for
improving the health status of a community

32. Uses of Epidemiology-
2. Planning and evaluation of health services:
Any planning process will need accurate information
about the socio-demographic profile, diseases, healthcare
facilities, communications, etc.
Similarly, while evaluating a health program, we will again
need current information about various diseases and
compare it with the “baseline” state that existed when we
started the program.
This quantified and summarized information is available
only through epidemiology.

33. Uses of Epidemiology-
3. Developing health policies:
Epidemiology is indispensable for making assessment of
community “diagnosis” and “needs.”
In addition, it provides “evidence-based” decisions about
the risks to the individuals and communities due to
various exposures.
These two facts make it a key discipline for developing
public health policies.

34. Uses of Epidemiology-
4. Study of the natural history of diseases:
What we know today of the natural course of HIV or
pulmonary TB or any other human disease has been made
possible by systematic observations on hundreds and
thousands of patients and description of the summarized
findings from these observations on the large number of
patients, which is possible only by epidemiological
methods.

35. Uses of Epidemiology-
5. Searching for the causes and risk factors of diseases:
How do we say that smoking is a cause of IHD? Or obesity
is a risk factor for diabetes? It is by observing thousands
of obese and non-obese people and following them to see
what percentage in each group develops diabetes (cohort
epidemiological approach) or else by asking hundreds of
IHD people compared to hundreds of healthy people about
their smoking history (case–control epidemiological
approach).

36. Uses of Epidemiology-
6. Historic study of rise and fall of diseases:
Smallpox rose to its peak, killed millions, and was finally
eradicated; plague almost vanished after killing a huge
proportion of humanity and then reappeared. Epidemiological
studies of such rise and fall of diseases are essential to
understand the various factors that can be effectively utilized
in preventing the occurrence or re-emergence of other
diseases.

37. Uses of Epidemiology-
7.To identify syndromes:
A “syndrome” means simultaneous occurrence of two or
more different medical phenomena (constellations of
signs/symptoms) more frequently than what can be
accounted for by simply a “chance” association. It is only
after obtaining data on hundreds of patients from various
countries about signs and symptoms of a related nature,
through epidemiological methods, that we are able to put the
pieces of information together and identify “syndromes” and
their etiological factors. E.g., the initial single entity, “peptic
ulcer” was distinguished as two entities (duodenal and peptic
ulcer).

38. Uses of Epidemiology-
8.Investigations of epidemics and other field
investigations:
Epidemiology originally started as a science dealing
with investigations of epidemics; even now, it remains
one of its most important aims.
9.Surveillance for diseases:
In addition to the investigation of epidemics, disease
surveillance is another important function for which
epidemiology came into being. Surveillance
essentially monitors trends in the occurrence of

39. Uses of Epidemiology-
10. Making projections:
Quite often, we hear that there will be so many million
cases of IHD in a country by 2025 and so on! These
projections are made on the basis of mathematical models
developed by epidemiologists after collecting data from
large populations for the past many years.
11. Assessing the programs for mass screening for
diseases:
Based on epidemiological principles of “diagnostic test
assessment,” the mass screening programs are planned
and subsequently evaluated for their effectiveness in large
population groups.