The First session in the Epidemiology Lecture Series
Defining Epidemiology. Keywords in the definition. Aims of Epidemiology, Epidemiological Approach & Reasoning
4. Premise
underlying
Epidemiology
Disease, Illness, and Ill health
are not randomly distributed in human populations
Each of us has certain characteristics
that predispose us to, or protect us against
a variety of different diseases
These characteristics
may be primarily genetic in origin or
may be the result of exposure to certain environmental hazards
Perhaps most often, an interaction of genetic and environmental factors
5. Epidemiology
Study of the distribution and determinants
of health-related states or events
in specified populations
and the application of this study
to control of health problems
6. Study of how disease
is distributed in populations and
the factors that influence or
determine this distribution
Epidemiology
7. Epidemiology
Study of the distribution and determinants
of health-related states or events
in specified populations
and the application of this study
to control of health problems
10. Frequency
Disease / Disability / Death
Health related Events / States
Developing definition of disease
Instituting mechanism for counting cases
Determining the size of the population
Rates / Ratios
18. Three closely interrelated components
Frequency
Distribution
Determinants
Fourth Component - Unique to Epidemiology
Human Population
Fifth Component - Application
Disease Control / Prevention
20. Objectives of Epidemiology
1 to identify the etiology or cause of a disease and the relevant risk
factors—that is, factors that increase a person’s risk for a disease
2 to determine the extent of disease found in the community
3 to study the natural history and prognosis of disease
4 to evaluate both existing and newly developed preventive and
therapeutic measures and modes of health care delivery
5 to provide the foundation for developing public policy relating to
environmental problems, genetic issues, and other considerations
regarding disease prevention and health promotion
21. Aims of Epidemiology
1. to describe the distribution and magnitude of health and
disease problems in human populations
2. to identify aetiological factors (risk factors) in the pathogenesis
of diseases
3. to provide the data essential to the planning, implementation
and evaluation of services for the prevention, control and
treatment of disease and to the setting up of priorities among
those services
22. Ultimate Aim of Epidemiology
• to eliminate or reduce the health problems or its consequences
• to promote the health and well-being of society as a whole
24. The first step is to determine whether an association exists between
exposure to a factor (e.g., an environmental agent) or a characteristic of
a person (e.g., an increased serum cholesterol level) and the
development of the disease in question.
The second step is to try to derive appropriate inferences about a
possible causal relationship from the patterns of the associations that
have been found
25. Epidemiologic Reasoning
• Process begins with the suspicion
• Possible influence of a particular factor
on the occurrence of the disease
Suspicion may arise from
Clinical Practice
Examination of Disease Patterns
Observations from Laboratory Research
Theoretical Speculations
27. Asking Questions
Related to Health Events
What is the event?
Where did it happen?
When did it happen?
How much is the magnitude ?
Why did it happen ?
So, what is to be done?
28. Asking Questions
Related to Health Action
What can be done to reduce the problem and its consequences?
How can it be prevented in the future?
What action should be taken by the community? By the health
services? By other sections? Where and for whom these activities be
carried out?
What resources are required? How are the activities to be organised?
What difficulties may arise, and how might they be overcome?
29. Making Comparisons
Between
Two subgroups in the population
Affected and Not Affected
Exposed and Not Exposed
Intervention and Without Intervention
Comparability
Standarisation
31. Epidemiology often begins with descriptive data
The first question to ask when we see
differences between two groups or two regions or over time is,
“Are these differences real?”
Are the data from each area of comparable quality?
Before we try to interpret the data, we should be satisfied that the data are valid.
If the differences are real, then we ask,
“Why have these differences occurred?”
Are there environmental differences between high-risk and low-risk areas, or
are there differences in the people who live in those areas?
This is where epidemiology begins its investigation!!
33. Psycho Endo Neuro Immunology
Study of the interaction between psychological
processes and the nervous and immune systems
of the human body
35. Social Inequity - Psychobiological Mechanism - Illness
People’s perception & experience of their place
in social hierarchies
Stress from the ‘Social Environment’
Affects Neuroendocrine functions
Alters host susceptibility
Increases human’s vulnerability to disease