Epidemiology is defined as the study of disease distribution and determinants in populations. It has three main components: studying disease frequency through rates and ratios, studying disease distribution patterns over time, place and people, and determining disease causative factors through analytical studies. The overall aims are to describe health problems, identify risk factors, and provide data to help prevent and control diseases.

1. Principles of Epidemiology
&
Epidemiologic methods

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3. Introduction
• Epidemiology began
with Adam & Eve
• Epi- Among, Demos-
people, logos- study)
• Foundation laid in 19th
century.

4. Definition
• “The study of the distribution &
determinants of health-related states or
events in specified populations, and the
application of this study to the control of
health problems.” (John M. Last, 1988)
• Three components:
– Studies of disease frequency,
– Studies of the distribution and
– Studies of the determinants.

5. Disease frequency
• Measurement of frequency of
– Disease, disability, death
• Summarizing these in terms of rates & ratios.
• Essential for comparing with diff. population /
subgroup of the same population.
• May yield important clues to disease
aetiology & development of strategies for
disease prevention / control.

6. Distribution of Disease
• Disease / health related matters not uniformly
distributed in the populations.
• It occurs in patterns in a community &, study of
these patterns in terms of time, place & persons
may lead to the hypotheses about risk /
causative factors and leads to measures for
control / prevention of the diseases.
• This part of epidemiology “Descriptive
epidemiology”

7. Determinants of diseases
• Test etiological hypotheses and identify
the underlying risk / causative factors of
the disease.
• Analytical epidemiology.
• Help in development of health programs,
interventions & policies.

8. Aims of Epidemiology
• To describe the distribution & magnitude of
health & disease problems in human
populations.
• To identify etiological factors / risk factors in the
pathogenesis of disease
• To provide the data essential to the planning,
implementation & evaluation of services for the
prevention, control and treatment of diseases
and to the setting up of priorities among those
services.