This document provides an overview of epidemiology including: 1. It defines epidemiology as the study of disease distribution and determinants in populations in order to control health problems. 2. The three pillars of epidemiology are measuring disease frequency, distribution, and determinants. 3. Key epidemiological methods are observational studies like cohort and case-control studies, and experimental randomized controlled trials.

1. Principles and Methods of
Epidemiology
RDM 205
Rural Health and Well-being
Dr. Rajeev Kumar,
M.S.W., (TISS, Mumbai), M.Phil., (CIP, Ranchi), U.G.C- J.R.F.,
Ph.D., (IIT Kharagpur)

2. “ I kept six honest serving men;
they taught me all I know. Their
names are what, why, when,
how, where, and who.”

3. What is Epidemiology?
 As defined by John M. Last (1988)
“ Epidemiology is the study of the
distribution and determinants of health
related states or events in specified
populations, and the applications of
this study to control of health related
problems”

7. Three pillars of Epidemiology
1. Disease frequency
2. Distribution of disease
3. Determinants of disease

8. Disease frequency
 Epidemiology is the measurement of
frequency of disease, disability or
death and summarizing this
information in form of rates and ratio.
(details will be discussed later)

9. Distribution of disease
 Disease or health related matter are
not uniformly distributed in human
population.
 Those are distributed in patterns in
community, and epidemiology address
those variations or patterns.
 This aspect is known as descriptive
epidemiology

10. Determinates of disease
 It identify the underlying causes ( or
risk factors).
 This is the real substance of
epidemiology

11. Aims of epidemiology
1. It describes the distribution and
magnitude of health and disease
problems in human population
2. To identify the aetiological factor (risk
factors) in the pathogenesis of
disease
3. To prove the data essential to the
planning, implementation and
evaluation of services for the
prevention, control, and treatment of
disease and to setting up of priorities
among those services

12. Epidemiology approach
1. Asking questions
2. Making comparisons

13. (A). Asking questions ( activity
based on given article)
 What is the event / problem?
 What is the magnitude ?
 Where did it happen?
 When did it happen?
 Who are affected?
 Why did it happen?

14. (B). Questions related to health
action ( activity based on given
article)
 What can be done to reduce the problem
and its consequence?
 How it can be prevented in the future ?
 What action should be taken by the
communities? By the health service? By
other sectors? Where and for whom
these activities be carried out ?
 What resources are required?
 How far the activities to be organized ?

15. Making comparisons
 There may be comparisons of two or
more groups
 There may be comparisons between
communities or regions or genders
 Before comparison, we need to
consider the comparability
 As is control and cohort studies ( will
be discussed later)

16. Basic measurements in
epidemiology
 Measurement of mortality
 Measurement of morbidity
 Measurement of disability
 measurement of presence, absence or
distribution of the characteristics or attributes
of the diseases
 Measurement of medical needs, health care
facilities utilization
 Measurement of the presence, absence or
distribution of the environmental and other
factors suspected of causing the disease.
 Measurement of demographic variables

17. Types of variables
 Variate: any piece of information
referring to the patients or disease, it
is of two types (1) discrete (2)
continuous
 Circumstance: Any factor in the
environment that might be suspected
of causing a disease ( air pollution,
polluted water)

18. Tools of measurement
 Rates
 Ratio
 Proportion

19. Rates
 Suppose there were 500 deaths from
traffic accidents in Ranchi..
 These are just number....
 It conveys no meaning to
epidemiologist
 It is not comparable with road
accidents deaths with another city
 Then what ????

20. What is rate??/
 Rate measures the occurrence of
some particular event in a population
during given time.
 It is statement of risk of developing a
condition
Death rate = number of death in one
year/mid-year population X 1000

21. Example of death rates

22. Specific death rates

24. Ratio

25. Proportion

26. Examples of proportion

27. incidence

28. Prevalence
 It refers specifically to all current
cases (old and new) existing at a
given point of time, over a period in a
given population
 It is of two types:
 1. Point prevalence
 2. period prevalence

32. Relationship between prevalence
and incidence

34. Epidemiological methods
 observational studies
 Experimental studies

35. Observational studies
 Cross-sectional studies
 Case control
 Cohort studies
 Longitudinal studies
 Types of cohort

36. Experimental studies
 Randomized control trial

37. Description of experimental
studies
 Dependent variable
 Independent variables
 Mediators /moderators variables
 What is randomization?
 What is control?
 What is blind?
 How many types of blind?
 Why there is blind?

38. Discussion and queries ???
Keep learning !!!