Epidemiology is the study of the distribution and determinants of health states or events in populations, aiming to control health problems through data on disease incidence, distribution, and progression. It employs observational and experimental methods to understand disease etiology and utilizes measurement tools like rates, ratios, and proportions for analysis. Key metrics include the infant mortality rate, case fatality rate, and maternal mortality rate, which help assess health outcomes in populations.

1. PRINCIPLES OF
EPIDEMIOLOGY AND
EPIDEMIOLOGICAL METHODS
Amit Singh
Msc
Nursing

2. EPIDEMIOLOGY
 Definitions
Study of the distribution and determinants of health states or
events in specified populations, and the application of this
study to control health problems, is termed epidemiology.
Parkin defined epidemiology (1873) as the branch of medical
science which treats epidemics.
Frost defined epidemiology (1927) as the science of the mass
phenomena of infectious diseases.
Greenwood defined epidemiology (1934) as the study of
Disease, any disease, as a mass phenomenon.
McMahon defined epidemiology (1960) as the study of
distribution and determinants of disease frequency in man.
 .

3. Aims of Epidemiology
The epidemiological studies aim to:
1) Study the incidence, distribution, and progression
of disease problems,
2) Describe the health status of human populations
in order to provide information for the planning,
evaluation, and management of health promotion
and re-built systems,
3) Provide data that may further be used for
identification of etiological factors of health and
disease.
4) Promote the use of epidemiological concepts for
management of health services.
.

4. METHOD OF
EPIDEMIOLOGY
Epidemiology An epidemiologist
studies the occurrence of diseases in
people who have been exposed to
various factors and conditions in the
past; and also identifies the factors
involved in the disease
etiology.Epidemiological studies are
either observational or experimental.

5. Basic Tools of Measurement
in
Epidemiology
By measuring central location, a single value is
obtained, which summarises the whole
distributed data.
While in case of frequency measure, only part of
the distribution is considered. In frequency
measures, one part of the distribution is
compared with another part of the distribution.
Or to the entire distribution. Rates, Ratios &
Proportions, are common frequency measures.

6. Rate
Rate is the frequency of a disease or
characteristic expressed per unit of size of the
population. It indicates the change that takes
place in a period. Rate may indicate mortality,
morbidity, etc., and population over a time
indicates risk of a particular event occurring.
Rate = (Number of events(deaths or disease) in
specified period /
Population at risk of the event or
disease

7. Infant Mortality Rate(IMR)-
IMR is the number of children dying at less
than 1 year of age, divided by the number of
live birth that year.
IMR= No. of deaths of children less then one year
of age X 1000
Number of live births in the same year
Case-Fatality Rate-
is the proportion of person with the disease
who die from it.
CFR= Number of deaths from disease X 1000
Number of confirmed cases of disease

8. Maternal mortality
Rate(MMR)
Mmr is the number of maternal death
during a given time period per
100,000 live birth during the same
time period.
MMR= Number of deaths assigned to
cause related to childbirth X 1000
Number of live births

9. RATIO
Ratio is the relative magnitude of two
quantities or a comparison of any
two values. It is cal –culated by
dividing one interval or ratio-scale
variable by the other.
Ratio= No of rate of events, items,
person in one group