epideniology for midwifery students].pdf

ambo university

1. EPIDEMIOLOGY
Tufa Kolola (MPH,
Asst. Prof.)
1

2. Course Objectives
§Understand the basic concepts of epidemiology
§Conduct common measures of occurrence of states of health
or disease
§Select study design appropriate to the research question and
mention the validity aspect of different design options
§Compute the most common effect measures and interpret the
results
§Identify sources of errors in epidemiologic study and critically
appraise research reports
§Describe the application of epidemiologic methods in public
health 2

3. Course contents
§Introduction to Epidemiology
§Communicable disease Epidemiology
§Measures of frequency and Disease
Occurrence
§Epidemiologic study design
3

4. Course Delivery & Evaluation
§Delivery
Lecture and Discussion
Reading assignment
§Assessment Methods
Continuous assessment
Final exam
4

5. §At the end of this section student will be able to:
vDefine Epidemiology
vDifferentiate descriptive and analytical
Epidemiology
vDescribe basic assumption of Epidemiology
vDescribe application of Epidemiology in public
health practice
vUnderstand concepts and theories of disease
causation
5

6. Definition of Epidemiology
§Originates from three Greek words.

Study upon populations
Classical definition.
epi demos
logy
on or upon people study
6

7. Modern definition
•The study of the frequency, distribution and
determinants of disease and other health related
events in specified human populations, and the
application of this study to prevent and control
of health problems.
7

8. 1. Frequency:
§It quantify how often a disease or other health related
events arises in a population (the magnitude of
occurrence)
Example:
oNumber of exposed people
oNumber of people with the outcome of interest
oProportion of exposed people
oProportion of people with the outcome of interest
8

9. 2. Distribution:
§It is the occurrence of diseases and other health
problems according to the characteristics of
person, place, and time
§ Attempts to answer who? Where? and when?
owho would be most likely to get the disease?
owhere would the disease be most likely to occur?
owhen would the disease be most likely to occur?
9

10. 2. Distribution:
§Variations in disease frequency by these three
characteristics provide useful information that helps:
Understand the health status of a population;
Formulate hypotheses about the determinants of
a disease;
And plan, implement, and evaluate public health
programs to control and prevent adverse health
events
10

11. 3. Determinants:
§Are factors that bring about a change in a
person’s health
§Both causal and preventive factors i.e. either
cause a healthy individual to become sick or
cause a sick person to recover
11

12. 4. Population:
§Populations are at the heart of all epidemiologic
activities
§Refers to a group of people with a common
characteristic such as place of residence, gender, age,
or use of certain medical services
§Epidemiology studies the health of the groups,
communities and whole or specific population
12

13. §Identify the causes of disease and the factors that increase
a person’s risk of disease
§Describe the health status of populations – person, place
and time
§Elucidate the natural history and characteristics of a
disease
§Evaluate effectiveness of health interventions/preventive
measures
§Supply information for decision
13

14. §Originally focused exclusively on epidemics of
communicable diseases
§Subsequently expanded to address non-communicable
diseases
§At present epidemiologic methods are being applied
to:
– Infectious and non infectious diseases
– Injuries and accidents
– Nutritional deficiencies
– Mental disorders
– Maternal and child health
– Congenital anomalies
– Cancer
– Occupational health
– Environmental health
– Health behaviors 14

15. 1. Descriptive Epidemiology – concerned with describing
the frequency and distribution of disease and other health
related events in relation to person, place and time
Person:
Place:
Time:
Who?
Where?
When?
15

16. Descriptive Epidemiology
16
What? Who? When? Where?
What are the
health problems
of the
community?
What are the
attributes of
these illnesses?
Who is
involved?
What are the
attributes of
affected persons?
Over what
period of time?
Where do the
affected people
live, work or
spend leisure
time?
§Deals with the questions:

17. Descriptive Epidemiology
§Tell us the magnitude or burden of health
problems
§Tells us the population at greatest risk of
acquiring the disease
§Generate hypothesis
17

18. 2. Analytic Epidemiology: concerned with comparison of
groups of individuals to identify determinants of diseases
and other health related events
§Deals with the questions:
18
Why? How?
What are the
causal agents?
What factors
affect outcome?
By what mechanism
do they operate?
§Test the hypothesis

19. an
antecedent
19

20. 1.Human disease does not occur at random
2.Human disease has a causal factors
3.These causal factors can be identified through
systematic investigation of populations
4.Human disease can be prevented (have
preventive factors)
20

21. How the disease is caused?
1.Supernatural theory of disease
2.Ecological theory
3.Germ theory
4.Multifactorial causation theory
21

22. §No unanimous opinion
§There are people in both developed and developing
countries still believe in supernatural origin
§ Even today superstitions are becoming major
obstacles in disease control
§Most of the literates view that disease is the result of
microbes
§Most of the uneducated people believe that disease is
due to bad physical environment
22

23. 1. Supernatural theory of disease
§In the early past, the disease was thought mainly
due to either the curse of god or due to the evil
force of the demons
§ Accordingly, people used to please the gods by
prayers and offerings or used to resort to witchcraft
to tame the devils
23

24. 2. Ecological theory
§Due to environmental influence (“Airs, Waters
and Places”)
§ It is the first scientific approach or reasoning
regarding disease causation.
24

25. 3. Germ theory
Robert Koch
•Microbes (germs) were found to be
the cause for many known diseases.

•Pasteur, Henle, Koch were the
strong proponents of microbial theory
after they discovered the micro-
organisms in the patients’ secretions
or excretion.

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26. Henle-Koch Postulates
Henle and Koch postulated that:
1.Each disease will be caused by a germ
2.Without that germ that disease will not be caused
3.By introducing that germ , that disease can be caused in animals
experimentally,
4.And that germ can again be isolated from that sick animal
experimented with.

cannot explain the etiology of all diseases
26

27. 4. Multifactorial causation theory
Pettenkoffer
•Pettenkoffer Stated that
agent, host and
environmental factors
will act and interact
synergistically and act as
joint independent partners
in causing the disease.
27

28. D
Agent
factors
Host factors
Environmental
factors
§Disease occurs when
host factors and
environmental factors
make the agent sufficient
enough to cause the disease
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29. 29
Thank you