MEASUREMENTS OF EPIDEMIOLOGY EPIDEMIOLOGY EPIDEMOLOGY IN NURSING

1. Measurement of
Epidemiology
BY ADNAN AKBAR

2. 2
objectives
At the end of this presentation, learners
will be able to:
 Define the term health and disease
 Identify the frequency of following
 Population
 Incidence
 Prevalence
 Mortality
 Morbidity
 Rate

3. 3
Health
 Health is a state of complete physical,
mental, and social wellbeing and not
merely the absence of disease or
infirmity.
(WHO, 1984)

4. 4
Health:
 Epidemiologists tends to be simple in define
health. For example
 “Disease Present”
 “Disease Absent”
(Bonita, Beaglehole, and Kjellstrom, 2006)

5. 5
Disease
 The definition of disease is usually based on a
combination of physical and pathological
examination, diagnostic test results, and signs and
symptoms.
 Which and how many criteria are used to define a
“case” (a person who needs the disease definition)
has important implication for accurately
determining.
(Aschengrau and Seage, 2008)

6. 6
Measuring disease frequency
 The measures of disease frequency are
based on the concept of prevalence and
incidence.
(Bonita, Beaglehole, and Kjellstrom, 2006)

7. 7
Population at risk
 population at risk includes people who are
potentially susceptible to the disease.
 For example: Men should not be included
when calculating the population at risk of
cervical cancer.
(Bonita, Beaglehole & Kjellstrom, 2006)

8. 8
Population at risk
Population at risk can be defined in terms of:
 Demographic factors
 Geographic factors
 Environmental factors
Example
 Occupational injuries occurs only among working
people.
 Brucellosis occurs only among people handling
infected animals.

9. 9
Rate:
 Rate is the number of event in the given population over a
given period of time or at a given point in a time.
 Epidemiologist are concerned with numbers, including the
numbers of health related events or number of cases or the
number of deaths.
There are general categories of rate are:
 Natality rate
 Morbidity rate
 Mortality rate

10. Cont….
 Rate is the most important epidemiological tool used for
measuring diseases. Rate is a special for proportion that
includes time. It is considered to be a basic measurement of
disease occurrence. Accurate count of all events of interest
that occur in a defined population during a specified period is
essential for the calculation of rate.
 Rate= Number of event in a specified period
 Population at risk of these events in a specified period.
 Example: The number of newly diagnosed pneumonia cases
in 1999 per 1000 under five children
10

11. Ratio:
A ratio quantifies the magnitude of one
occurrence or condition to another. It express
the relationship between two numbers in the
form of x:y
Example:
The ratio of male to female
M:F
11

12. 12
Incidents & Prevalence

13. 13
Incidence of disease:
The incidence of disease represents the rate of
occurrence of new cases arising in a given
period in a specific population.
 The term "attack rate" of often used instead of
incidence during the disease outbreak.

14. 14
Incidence/Attack Rate:
 Incidence or attack can be can be calculated
as the number of people affected divided by
the number exposed.

15. 15
Incidence:
 The units of incidence rate must always
include a unit of time (case per 10n and per
day, week, month, year, etc).
Number of new events in a specific period.
Number of persons exposed to risk during
this period.
incidence *10n

16. 16
Prevalence of disease:
 The prevalence of disease is the frequency of
existing cases in a defined population at a
given point in time.
Number of people with the disease or condition
at a specific time
Number of people with the disease or
condition at a specific time
*10n

17. 17
Prevalence
Several factors determine prevalence
including:
 The severity of illness
 The duration of illness
 The number of new cases

18. 18
Prevalence
Factors that can lead to increased prevalence
includes:
 In-migration of susceptible people
 Out-migration of healthy people
 In-migration of cases
 Increased in new cases
 Longer duration of the disease
 Prolongation of life of patients without cure
 Improved diagnostic facilities (better reporting)

19. 19
Prevalence
Factors that can facilitate in decreasing the
prevalence of disease includes:
 Shorter duration of disease of the disease.
 Fatality rate from disease.
 Decrease in new case.
 In-migration of healthy people.
 Out-migration of cases.
 Improved cure rate of cases.

20. 20
Incidence and prevalence:
The relationship between incidence and
prevalence varies among diseases.
Example:
 there may be low incidence and high
prevalence of a disease-Diabetes
 There may be high incidence and low
prevalence-Common Cold.

21. 21
Incidence and prevalence
 Date on prevalence and incidence becomes
more useful if converted into rates.
 A rate is calculated by dividing the number of
cases by the corresponding number of people
in the population at risk and is expressed as
cases per 10/100/1000/10,000 people.

22. 22
Incidence Prevalence
Numerator Number of new cases during
a specific period of time.
Number of existing cases of
disease at a given point of
time.
Denominator Population at risk Population at risk.
Focus Whether the event is a new
case.
Time of onset of the disease
Presence and absence of a
disease.
Time period is arbitrary.
Uses Express the risk of becoming
ill.
More useful for studies of
causation.
Estimate the probability of
the population being ill at the
period of time being studied.
Useful in the studies of the
burden of chronic disease.

23. 23
Mortality:
 The mortality rate refers to the death rate for
either all deaths or a specific cause of death.
Number of deaths during a specific period
Number of people at risk of dying during the same period.
*10n

24. 24
The disadvantage of crude mortality
rate is that it does not take into account
the fact that the chance of dying varies
according to age, sex, race, socio-
economic class, and other factors.

25. 25
 Death rates can be expressed for specific
group in a population. For example age and
sex specified death rates can be calculated by:
Total number of deaths occurring in a specific
age and sex group of the population in a
defined area during a specified period
Estimated total population of the same age
and sex group of the population in the same
area during the same period
*10n

26. 26
Infant Mortality:
 The infant mortality rate is commonly used as an
indicator of the level of the health in a community. It
measures the rate of death in children during the fist
year of life, the denominator being the number of
live births in the same year.
Number of deaths in a year of children
less than 1 year of age
Number of live births in the same year
*10n

27. 27
Maternal mortality:
 The maternal mortality rate refers to the risk
of mothers dying from causes associated with
delivering babies, complications of pregnancy
or child birth.
Number of maternal deaths from puerperal
causes in a given geographic area in a given year
Number of live births that occurred among the
population of the given geographic area during
the same year
*10n

28. 28
Morbidity:
 Morbidly data are often helpful in clarifying the
reasons for particular trend in mortality.
 The sources of morbidly data includes
 Hospital admissions and discharges
 Outpatient and primary healthcare consultation
 Specialist services (such as injury treatment)
 Registers of disease events (Such as cancer or
malformations)

29. Survey by USAID in Pakistan
29

30. Maternal Mortality:
The death of a woman while pregnancy or
within 42 days of termination of pregnancy
irrespective of the duration and site of the
pregnancy, from any cause related to or
aggravated by the pregnancy or its
management, but not from accidental or
incidental causes.
30

31. Maternal Mortality Ratio:
 Number of maternal deaths per 100,000 live
births
 276 deaths per 100,000 live births
 1 maternal death occurs every 30_40
minutes.
31

32. Maternal Death by Residence
32
14
23
20
0
5
10
15
20
25
Urban Rural Total
Percent of deaths
of women age 15-
49 years

33. Main causes of Maternal Deaths:
Most common direct causes of maternal
deaths are:
 Postpartum hemorrhage 27%
 Puerperal sepsis 14%
 Eclampsia/toxemia of pregnancy 10%
 iatrogenic causes 8%
33

34. When do women die during pregnancy
34
7
29
3
22 23
89
0
10
20
30
40
50
60
70
80
90
Pregnancy Delivery PostPartum
Urban
Rural

35. When do women die during pregnancy
and childhood
35
1114
7
3
6
8 7 4
66
27
8
11
0
10
20
30
40
50
60
70
Pregnancy Delivery Post
Partum
Punjab
Sindh
KhaberPakhtoonkha
Balochistan

36. Maternal mortality Ratio by Residence
36
175
319
276
0
50
100
150
200
250
300
350
Urban Rural Total
Maternal deaths per
100,000 live births for
the 3 years before the
survey

37. Child health and mortality
Childhood Mortality Estimates:
Neonatal mortality
 Probability of dying within 28 days of life
Post neonatal mortality
 difference between neonatal and infant mortality
Infant mortality
 probability of dying before the first birthday
37

38. Cont…
child mortality
 Probability of dying between age one and five
Under 5 mortality
 probability of dying before the fifth birthday.
38

39. Childhood mortality rates
39
54
24
78
18
94
0
10
20
30
40
50
60
70
80
90
100
Neonatal
Mortality
Postnatal
Mortality
Infant
Mortality
Child
Mortality
Under-5
Mortality
Frequency

40. Infant mortality rates
40
86
76
78
70
72
74
76
78
80
82
84
86
1992-1996 1997-2001 2002-2006
Infant
Mortality

41. Under 5 mortality rates
41
103
92 94
86
88
90
92
94
96
98
100
102
104
1992-
1996
1997-
2001
2002-
2006
Under-5
Mortality Rate

42. Gender and childhood mortality
42
57
48
23 25
14
22
0
10
20
30
40
50
60
Neonatal
mortality
Postneonatal
mortality
Child mortality
Male
Female

43. Summary of the findings:
Infant Mortality Rate:
78 deaths pre 1000 live births
Under 5 Mortality Rate:
94 deaths per 1000 live births.
Childhood mortality has not reduced significantly for the past 15
years
our current mortality rates are the second highest in Asia (after
Afghanistan) 43

44. Cont…
One in every eleven child in Pakistan dies before reaching age
five.
Over half of these deaths occur during the first month of life.
Childhood mortality is highest among children whose mothers
have No Education.
A major risk factor for infant mortality is a birth interval of less
than two years.
44

45. Cont…
Newborn Asphyxia, Sepsis and Prematurity
account for over 80% of all neonatal deaths.
Pneumonia and Diarrhea are responsible for
over half of all infant and child deaths.
There is a very close link between maternal and
child mortality with 40% of all still births
occurring during childbirth. 45

46. Cont…
The pattern and location of deaths suggest that
poor care seeking behavior as well as
quality of care in the health system are
important determinants of newborn and child
deaths.
46

47. 47
References:
 Aschengrau, A.& Seage, G. R. (2008).
 Essentials of epidemiology in public health
(2nd em). Sudbury: Jones and Bartlett
Publishe$.
 Bonita, R, Beaglehole, R, & Kjellstrom, T
(2006). Basic epimemiology (2nd em). India:
WHO Library Cataloguing.

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