2. Outline
• Definition of Epidemiology
• History of Epidemiology
• Scope of Epidemiology
• Uses of Epidemiology
• Fundamental Assumptions in Epidemiology
2
3. Objectives
At the end of this lesson, learners will be
able to:
– Define Epidemiology and its components
– Distinguish between descriptive and
analytic Epidemiology
– Understand history and scope of
Epidemiology
– Describe the basic assumption and uses
of Epidemiology
3
4. Introduction to Epidemiology
• Epidemiology – defined in so many ways!
• Epidemiology is the basic science of public health
• All the definitions are similar
– They focus on:
• Health promotion
• Disease prevention
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5. What is public health?
5
• The science and art of preventing disease,
prolonging life and promoting physical and mental
health and efficiency through organized efforts
and informed choices of society, organizations,
public and private, communities and individuals”.
6. • Epidemiology is:
– A quantitative basic science
– A method of causal reasoning
– A tool of public health action
6
7. • Public health differs from clinical medicine:
– Emphasis on prevention rather than
treatment
– Focus on populations rather than
individuals
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8. Epidemiology
• Definition
– Epidemiology is the study of frequency,
distribution and determinants of disease
and health related problems, and its
application to disease prevention and
health promotion in a specified population
– There are a lot of important terms here:
study, frequency, distribution, determinant,
health related problem, specified
population
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9. • Study
– Epidemiology is a scientific discipline
– It has sound methods of scientific
investigation at its foundation
– Also called the basic science of public
health
9
10. • Frequency
– It indicates the quantitative aspect of
Epidemiology
– Related to the number of health related
events
– Also the rate or risk of disease
– Can be split into morbidity and mortality
rates
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11. • Distribution
– Related to the pattern of health events
– Occurrence of health events by time,
place and personal characteristics
– Time (annual, seasonal, hourly
occurrences)
– Place (geography, urban-rural variation)
– Personal (age, sex, race)
11
12. • Determinants
– Causes, etiology, predisposing factors,
precipitating factors, etc.
– The domain of Analytic Epidemiology
– The response for how and why
questions
12
13. • Health related problems
• Specified populations
How do clinicians and epidemiologists
view a patient?
13
14. • Application
– Epidemiology is more than just ‘the
study of’.
– It provides data for directing public
health action
– It is an art as well as a science
14
15. • Sometimes Epidemiology is described by the type
of studies it is composed of
• The key features of epidemiological studies
– Quantitative rather than qualitative
– Observational rather than experimental
– Population based rather than individuals
15
16. • Epidemiology has two major branches:
– Descriptive Epidemiology
• What
• Who
• When
• Where
– Analytic Epidemiology
• How
• Why
16
17. • Examples of Analytic Epidemiology
– Studying the effects of factors on
disease occurrence
– Studying the etiology of a particular
disease
– Verifying the efficacy of a particular
vaccine trial
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18. History of Epidemiology
• Epidemiology originated from Hippocrates’
observation more than two millennia ago.
– Environmental and host factors
influence disease occurrence
– Disease occurrence was explained from
a rational instead of a supernatural
viewpoint
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19. • Mortality data analysis was tried in Britain in the
17th century
• In the 19th century
– An extensive work on mortality data
analysis
– Measurement of disease conditions in
specified human populations
– Marked the formal beginnings of
Epidemiology
– Heralded many fantastic epidemiologic
achievements
19
20. • John Snow
– Assessed cholera epidemic in London in
the mid-19th century(1854)
– This assessment is an important
epidemiologic milestone in history
– It earned him the title ‘the father of field
epidemiology’
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21. • Late 19th century and early 20th century
– Comparison of disease rates in subgroups of
populations became popular
– An important tool of linking environmental
factors with specific diseases
• 2nd half of 20th century
– Comparison of disease rates advanced to non
communicable chronic diseases
21
22. • Epidemiology in recent years
– A quantitative science
– Focuses on prevention and control of
diseases
– The association between cigarette
smoking and lung cancer is a recent
Epidemiologic achievement
• Done using long term epidemiological cohort
studies
– Small pox eradication in the 1960s and
1970s
22
23. • Communicable disease epidemiology has become
a vital discipline because of
– HIV/AIDS
– Tuberculosis
– Malaria
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24. Scope of Epidemiology
• A number of transitions have been seen
in the history of Epidemiology:
– Epidemiology was initially linked to the study of
epidemic diseases mostly of communicable
nature
– Later on other diseases of non communicable
nature were included in the scope
– At present epidemiologic methods are being
applied to:
• Injuries and accidents Nutritional
deficiencies
• Mental disorders MCH
• Congenital anomalies Cancer
• Occupational health Environmental health
• Health behaviours
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25. Uses of Epidemiology
• Epidemiology has a big list of uses some
of which are:
– Monitoring the public health
– Studying the natural history of diseases
– Looking for causes of disease, death and
disability – etiological agents
– Evaluating interventions and health service
provision
– Planning health services
– Decision making in clinical medicine
25
26. Fundamental Assumptions in
Epidemiology
• Human diseases do not occur at random!
• Human diseases have causal and
preventive factors that can be identified
through systematic investigations!
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27. Assignment
27
– Q1. Who are some of the scientists who
shaped epidemiologic thought? Discuss
their contribution
– Q2. Discuss How John Snow Assessed
cholera epidemic in London in the mid-19th
century(1854)
– Q3. Discuss the special fields of
epidemiology and their scope?
