1. UNIT-IV
EPIDEMIOLOGY FOR ANP
COURSE
INTRODUCTION ABOUT
EPIDEMIOLOGY
DR.ANJALATCHI MUTHUKUMARAN
VICE PRINCIPAL
ERA COLLEE OFNURSING
ERA UNIVERSITY , LUCKNOW -226003

2. Content of the chapter
 Introduction, epidemiology description,Scope,
epidemiological approach and methods,
 Morbidity, mortality,
 Concepts of causation of diseases and their
screening,
 Application of epidemiology in health care
delivery,
 Health surveillance and health informatics
 Role of nurse.

3. Learning objective
Introduction about epidemiology :
 Introduction
 Abbreviation
 Definition /meaning
 Aim /ultimate aim
 Terminology used in this chapter
 Use of epidemiology
 Level of prevention

4. Introduction of epidemiology
 The Greek physician Hippocrates is
sometimes said to be the father of
epidemiology.
 He is the first person known to have examined
the relationships between the occurrence of
disease and environmental influences.
• epi – means “on, upon, befall”
• demo – means “people, population, man”
• logy – means study

5. Definition of Epidemiology
 Definition of Epidemiology:- The study of
frequency, distribution and determinants of
diseases is known as epidemiology.
(International epidemiological association)

6. Key Words of Epidemiology
• Epidemic : ( Epi = upon : demos = people ) An
outbreak of disease in a community in excess of
“normal expectation ”
• Endemic: (en = in; demos = people). The constant
presence of disease within a geographic area or
the usual prevalence of a given disease in a
particular area. malaria, tuberculosis, etc.
• Pandemic: (pan = all: demos = people) An
epidemic which spreads from country to country
or over the whole world, as for example, the
recent epidemic of Covid -19 exposure .

7. Aims of Epidemiology
•To describe the distribution and size of disease
problems in human population.
• To identify etiological factors in the
pathogenesis of disease.
• To provide data essential to the planning,
implementation, and evaluation of services for
the prevention, control and treatment disease
and to setting up the priorities among these
services.

8. The ultimate aims of
epidemiology
 The ultimate aims of epidemiology can be
concluded in to two followings points
 To eliminate or reduce the health problem or
its consequences .
 To promote the health and wellbeing of society
as a whole.

9. Uses of Epidemiology
•To study the effects of disease state in a
population over a time and predict future
health.
• To diagnose the health of the community.
• To evaluate health services.
• To estimate the individual risk from group
experiences.
•To identify the syndrome.
•To search for causes of disease.

10. Components of epidemiology
1.Disease frequency: -
• The core characteristics of epidemiology are to measure the
frequency of diseases, disability or death in at the frequency
of diseases, disability or death in a specified population. it is
always as the rate, ratio and specified population. it is always
as the rate, ratio and proportion..
• Much of the subject of epidemiology subject matter of
measurement of diseases and health related events falls in
the domain of biostatistics, which is a basic tool of in the
domain of biostatistics, which is a basic tool of epidemiology.
This helps to development of strategies epidemiology.
This helps to development of strategies for prevention or control
of health related problems .

11. 2.Distribution of diseases:
 Distribution of diseases: -
 Health events occur in pattern in community and this pattern varies
from community to community. .
 Also health events or diseases condition affect population at various
age groups, different sexes, different subgroups of population.
 Distributions of events are based on time, place, and person. We
can analyze whether any increases or decreases occur for a
particular condition.
 . Epidemiology addresses itself to a study of these variations or
patterns, which may suggest or lead to of these variations or
patterns, which may suggest or lead to measure to control or
prevent the diseases.
 An important measure to control or prevent the diseases.
 An important outcome of this study is formulation of etiological
hypothesis..

12. 3.Determinants of diseases
• Epidemiology helps in identifying the causative
agent or the risk/predisposing factors of agent
or diseases .
•This is one of the real uses of epidemiology.
Understanding the factors leading to any
programs for the control of those diseases.

13. Levels of Prevention
•Primary prevention Health promotion Specific
protection
•Secondary prevention Early diagnosis
(screening tests, case finding programmes )
Adequate treatment
•Tertiary prevention Disability limitation
Rehabilitation – Functional rehabilitation –
Vocational rehabilitation – Social rehabilitation
– Psychological rehabilitation

14. Learning objective for
epidemiology approach
 Introduction
 Definition
 Epidemiology approach
 Asking question
 Making comparisons

15. Epidemiological approach
1. Asking questions
2. Making comparisons
1. Asking questions Epidemiology has been
defined as a means of learning or asking
questions.. and getting answers that lead to
further questions

16. RELATED TO HEALTH EVENTS
•What is the event? (the problem)
•Where did it happen?
•When did it happen?
•Who are affected?
•Why did it happen?

17. RELATED TO HEALTH
ACTIONS
•What can be done to reduce this 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 sectors ?
•What resources are required ?
How are the activities to be organized ?

18. 2. Making comparisons
•This approach is to make comparisons and
draw inferences.
•Comparison may be made between different
population at a given time eg. Rural with urban
population
•Between sub group of population eg. Male with
female population
•Between various periods of observation eg.
Different seasons ,

19. Learning objectives
tools of measurement
 Introduction
 Definition
 Tool of measurement
 Rate
 Ratio
 Proportion

20. Tools of measurement
1. Rates
2. Ratios
3. Proportions
Rates :
 A rate measures the occurrence of some
particular event (development of disease or
the occurrence of death) in a population during
a given time period.
 Number of deaths in one year Death rate = X
1000 Mid - year population

21. Rates are continued
 (1) Crude rates: These are the actual observed
rates such as the birth and death rates. Crude
rates are also known as unstandardized rates.
 (2) Specific rates: These are the actual observed
rates due to specific causes (e.g., tuberculosis); or
occurring in specific groups (e.g., age-sex groups)
or during specific time periods (e.g.. annual,
monthly or weekly rates).
 (3) Standardized rates: These are obtained by
direct or indirect method of standardization or
adjustment, e.g., age and sex standardized rates.

22. 2.RATIO
 Another measure of disease frequency is a
ratio.
 It expresses a relation in size between two
random quantities.
examples include:
•The number of children with malnutrition at a
certain time
• sex-ratio, doctor population ratio, child woman
ratio, etc

23. 3.PROPORTION
 A proportion is a ratio which indicates the
relation in magnitude of a part of the whole.
The numerator is always included in the
denominator.
 A proportion is usually expressed as a
percentage.
Example : The number of children with scabies
at a certain time x 100, divided by , The total
number of children in the village at the same
time

24. Learning objectives
mortality rate
 Introduction
 Definition
 Meaning of mortality
 Limitation
 Mortality rate and ratio

25. MORTALITY
 The occurrence of death in a population.
Mortality data are relatively easy to obtain,
and, in many countries, reasonably accurate.
Many countries have routine systems for
collecting mortality data each year, information
on deaths is analyzed and the resulting
tabulations are made available by each
government.

26. Limitations of mortality data
• Incomplete reporting of deaths
• Lack of accuracy:-inaccuracies in the recording
of age and cause of death
• Lack of uniformity:- There is no uniform and
standardized method of collection of data
• Changing:- Changing coding systems and
changing fashions in diagnosis may affect the
validity.
• Diseases with low fatality:-the disease is
associated with low fatality (e.g., mental
diseases, arthritis).

27. MORTALITY RATES AND
RATIOS
 1. Crude death rate The simplest measure of
mortality is the crude death rate
 It is defined as the number of deaths (from all
causes) per 1000 estimated mid-year
population in one year, in a given place.
 Number of deaths during the year = X 1000
Mid-year population

28.  2. Specific death rates When analysis is
planned to throw light on aetiology, it is
essential to use Specific death rates.
 The specific death rates may be
 (a) cause or disease specific e.g., tuberculosis
cancer, accident;
 (b) related to specific groups e.g. age-specific,
sex-specific , age and sex specific, etc.

29.  3. Case fatality rate (Ratio) Case fatality rate
represents the killing power of a disease.
 It is simply the ratio of deaths to cases.
 The time interval is not specified.
 Case fatality rate is typically used in acute
infectious diseases (e.g., food poisoning,
cholera, measles)
 Total number of deaths due to a particular
disease = X 100 Total number of cases due to
the same disease

30. 4. Proportional mortality rate (Ratio)
•It is sometimes useful to know what proportion of
total deaths are due to a particular cause (e.g..
cancer) or
•what proportion of deaths are occurring in a
particular age group (e.g., above the age of 50
years).
•Proportional mortality rats expresses the number
of deaths due to a particular cause (at in a specific
age group) per 100 (or 1000) total deaths.
Thus we have:
(a) Proportional mortality from a specific disease
Number of deaths from the specific disease in a
year = X 100 Total deaths from all causes in the

31.  2. Under 5 proportionate mortality rate Number
of deaths under 5 years of age in the given
year. = X 100 Total number of deaths during
the same period
 3. Proportional mortality rate for aged 50
years and above Number of deaths at persons
aged 50 years and above = X 100 Total deaths
at all age groups in that year

32.  5.Survival rate It is the proportion of survivors
in a group, (e.g. of patients) studied and
followed over a period tag, a 5 year period.
Survival rates have received special attention
in cancer studies.
 Total number of patients alive after 5 years
Survival rate = X 100 Total number of patients
diagnosed or treated

33. Learning objective
morbidity
 Introduction
 Definition/meaning
 Morbidity
 Incidence
 Prevalence

34. MORBIDITY
 The occurrence of an illness or illnesses in a
population. Morbidity has been defined as any
departure, subjective or objective, from a state of
physiological well-being.
 The term is used equivalent to such terms as
sickness. illness, disability etc.
 WHO Expert Committee on Health Statistics noted in
its 6th Report that morbidity could be measured in
terms of 3 units
 (a) persons who were ill
 (b) the illnesses (periods or spells of illness) that these
persons experienced; and
 (c) the duration (days, weeks, etc.) of these illnesses

35. INCIDENCE
 Incidence rate is defined as the number of NEW
cases occurring in a defined population during a
specified period of time .
 It is given by the formula : Number of new cases
of specific disease during a given time period
Incidence = X 1000 Population at risk during that
period
 For example:- if there had been 500 new cases of
an illness in a population of 30,000 in a year, the
incidence rate would be: = 500/30,000 x 1000 =
16.7 per 1000 per year

36. PREVALENCE
The term "disease prevalence" refers specifically to all current
cases (old and new) existing at a given point in time, or over
a period of time in a given population.
(a) Point prevalence
(b) Period prevalence
(a) Point prevalence :
Point prevalence of a disease is defined as the number of all
current cases (old and new) of a disease at one point of
time, in relation to a defined population. several days, or
even a few weeks.
Point prevalence is given by the formula: Number of all current
cases (old and new) of a specified disease existing at a
given point in time X 100 Estimated population at the same
point in time Conti..

37. (b) Period prevalence A less commonly used
measure of prevalence is period prevalence. It
measures the frequency of all current cases
(old and new) existing during a defined period
of time (e.g., annual prevalence) expressed in
relation to a defined population. cases arising
during the year.
Period prevalence is given by the formula:
Number of existing cases (old and new) of a
specified disease during a given period of time
interval X 100 Estimated mid interval
population at risk

38. Leaning objectives
epidemiological methods

39. METHODS OF
EPIDEMIOLOGICAL STUDIES
 Epidemiologists employ three different
methods or approaches for epidemiological
studies which are:
 1. Descriptive method
 2. Analytical method.
 3. Experimental method

40. 1. Descriptive Method
 Descriptive method of epidemiological study is
concerned with the study of frequency and
distribution of disease and health related
events in population in terms of person, place
and time.
 This method gives information about which all
are affected by a particular disease or health
related event or problems, where the cases
occur and when they occur.
 The data is collected about:

41. • Personal characteristics such as age, sex,
race, marital status, occupation, education,
income, Class, dietary pattern, habits.
• Place distribution of cases i.e. areas of high
concentration, low concentration and spotting
in the map.
• Time distribution/trends such as year, season,
month, week, day and hour of onset of the
disease.

42.  Such information’s give clue to possible
associated factors such as age with specific
disease e.g. measles, diphtheria, pertusis in
early childhood, cancer in middle age,
arterioscleroses in old age, some habits like
smoking with lung cancer, dietary pattern with
obesity.
 The data collected are analyzed and
presented in terms of percentages, rates and
ratios

43.  Cross-sectional studies In this design of
descriptive method of study, the data is collected
from a cross-section of population at a one point
in time. The results of the study are applied on the
population.
 The cross-section of the population is sampled
carefully so that it is representative of the whole
population.
 Cross-section study is like a snapshot and
provides information about the prevalence of a
disease.
 It is also called as prevalence study. example
study of diabetes or hypertension by personal

44.  Longitudinal Studies Longitudinal studies art
useful for studying the natural history of
diseases, finding out incidence rates of
diseases and identifying risk factors of
diseases.
 Longitudinal studies are more expensive and
time consuming than cross- sectional studies.

45. 2. Analytical Method
 You have learn that descriptive studies generate
etiological clues for various diseases help in
formulating a guess or hypothesis for further
vigorous study or testing e.g. "Cigarette smoking
(10 to 20 in a day) causes lung cancer in 10 to
15% of smokers after 20 years of exposure”, wife
battering is related to violence in victim's
childhood family of origin".
 These types of hypothesis are further studied and
tested by analytical studies to determine the
association of cause with the effect.

46. Case control study
 In this method a group of people who have
been diagnosed as having a particular
problem e.g. lung cancer (cases) are
compared with a group of people who are
similar in characteristics to that of cases but
they are free from the problem i.e. free from
lung cancer under study (controls).

47. Cohort Study
 A cohort is a specific group of people, at a
certain time, sharing common characteristics
or experience e.g.
 people born on the same day or the same year
(birth cohort),
 couple married in the same year (marriage
cohort),
 a class of nursing students (experience
cohort),
 people With same occupation (occupation
cohort) etc.

48.  a) Prospective cohort study: Cohort study is
prospective in nature because the group under
study is free from the disease but exposed to
risk factor and epidemiologist study the
development of a condition over time.
example-lung cancer
 b) Retrospective cohort study: This is also
called as historical cohort study. In this type of
study designs the event has already occurred

49. Experimental Method
• Experimental studies are similar in approach to cohort
studies except that conditions are under the careful
control of investigator.
• Experimental studies are done to confirm the etiology
of diseases,' establish the efficacy of preventive or
therapeutic measures and evaluate health care
services.
• These' studies are done under controlled conditions.
• The investigator administers an intervention/gives
treatment to the experimental group which is either
exposure to causative factor of disease or
preventive/therapeutic measure to improve or
influence health or prevent disease but not to the
control group which is similar to experimental group in
all its aspects.