Introduction to Epidemiology and Basic Measurement like, rate,ratio, proportion, incidence and prevalence

1. Dr. Animesh Gupta
MBBS, MD, FDM, FAGE
Assistant Professor, Dept. of Community Medicine, SIMS & RC
Epidemiology - Dr. Animesh Gupta
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2. ▪Pessimist: The glass is
half empty.
▪Optimist: The glass is
half full.
▪Epidemiologist: As
compared to what?
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3. EPI DEMO LOGOS
Upon, on People, population, man the Study of
The study of anything that happens to
people
“That which befalls man”
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4. Hippocrates(460-370 BC )
▪ Greek physician
▪ “Father of Medicine”
▪ Recognized association of disease with place
(geography), climatic conditions, water, eating
habits and housing.
.
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5. ▪Louis Pasteur : Germ theory of disease
▪Robert Koch : 4 postulates to prove an
infectious agent causes a particular disease
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6. John Snow (1813-1858)
▪ “Father of Epidemiology”
▪ 20 yrs before discovery of
microscope, conducted studies
of cholera out breaks.
▪ Used spot maps to show case
distribution.
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8. "The study of the distribution and determinants of
health-related states in specified populations, and
the application of this study to control of health
problems."
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*Last, J.M. 1988. A Dictionary of Epidemiology, 2nd ed.
Epidemiology - Dr. Animesh Gupta

9. DYNAMIC STUDY OF THE
FREQUENCY
DISTRIBUTION
DETERMINANTS
CONTROL
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OF HEALTH AND DISEASE
IN A POPULATION
Epidemiology - Dr. Animesh Gupta

10. ▪Frequency of disease, disability, death..
▪Expressed as rates & ratios
- prevalence, incidence, death rate.
▪Used to make comparisons
- Gives clues to etiology.
▪Helps in development of strategies
for prevention &control programme.
▪Health related events- health need , demands…
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11. ▪Formulation of etiological hypothesis
▪“Descriptive epidemiology”
▪Time Place and Person distribution of disease
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12. ▪To test etiological hypothesis
▪Identify underlying
causes (risk factors)
▪“Analytical epidemiology”
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13. ▪To describe the distribution and magnitude of health and disease
problems in human populations
▪To identify etiological factors ( risk factors ) in the pathogenesis of
disease.
▪To provide the data essential for the planning , implementation
and evaluation of services for the prevention ,control and
treatment of diseases and to set up priorities among those
services.
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14. A. Asking questions
B. Making comparisons
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15. a) What is the event ?
b) What is its magnitude ?
c) Where did it happen ?
d) When did it happen ?
e) Who are affected ?
f) Why did it happen ?
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16. a) What can be done to solve this ?
b) How can it be prevented ?
c) What action can be taken ?
d) What resources are required ?
e) What difficulties may arise and how to solve them ?
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17. a. Groups having and not having the disease
b. Randomization
c. Matching
d. Standardization
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18. DESCRIPTIVE Health and disease in the community
What? Who? When? Where?
What are the
health problems
of the
community?
What are the
attributes of
these illnesses?
How many
people
are affected?
What are the
attributes of
affected
persons?
Over what
period of time?
Where do the
affected
people
live, work or
spend leisure
time?
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19. 1. To describe the frequency and extent of health conditions
and disease.
2. To determine the burden of disease in a community,
including socioeconomic impact of disease occurrence in
specific populations.
3. To identify the causes and risk factors of specific
diseases.This is the basis of disease prevention.
4. To evaluate medical interventions, including both
preventive and therapeutic measures, and evaluate the
delivery of these measures in health care settings.
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20. 5. To study the natural history and prognosis of disease.
6. To provide the foundation for developing public policy
and regulatory decisions relating to health.
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21. ▪Descriptive
▪Analytic
▪Experimental
▪Study of the occurrence and
distribution of disease
▪Further studies to determine the
validity of a hypothesis concerning
the occurrence of disease.
▪Deliberate manipulation of the cause
is predictably followed by an
alteration in the effect not due to
chance
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22. OBSERVATIONAL STUDIES
DESCRIPTIVE STUDY ANALYTICAL STUDIES
✓ TIME
✓ PLACE
✓ PERSON
➢ ECOLOGICAL STUDY
➢ CROSS SECTIONAL STUDY
➢ CASE-CONTROL STUDY
➢ COHORT STUDY
EXPEREMENTAL STUDIES
➢ RANDOMIZED CONTROLLED TRIAL (RCT)
➢FIELD TRIAL
➢COMMUNITY TRIAL
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23. Measurement of
▪ Mortality
▪ Morbidity
▪ Disability
▪ Presence or absence or distribution of characteristic or
attributes of disease
▪ Health care or health utilization
▪ Demographic variables
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▪ Incidence – the no. of NEW cases
occurring in a defined population
during a specified period of time".
▪ Prevalence – all current cases (old
and new) existing at a given point in
time, or over a period of time in a
given population.
▪ Prevalence = Incidence * Duration of
illness

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26. ▪Rate
▪ It measures the occurrence of particular event in a population
during given time period.
▪ A rate comprises the following elements - numerator, denominator,
time specification and multiplier.
▪ Example:
Death rate = No. of death in a year/ Mid year population * 1000
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27. ▪Ratio
▪ It expresses a relation in size between two random quantities.
▪ The numerator is not a component of the denominator.
▪Proportion
▪ It is a ratio which indicates the relation in magnitude of a part of the
whole.
▪ The numerator is always included in the denominator.
▪ It is usually expressed as a percentage.
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