UNIT V EPIDEMIOLOGICAL TRANSITIONS IN DISEASE PATTERNS.pdf

Epidemiological Transition in Disease
Pattern
Unit V
BURHAN UDDIN, Karachi 1

Objectives
At the completion of this unit learners will be to;
 Define epidemiological transition.
 Compare developed vs developing nation
 Describe different stages of epidemiological transition.
 Define Population changes and population pyramid
 Explain difffent types of population pyramid.
 Illustrate Factors affecting population change (dependency ratio,
sex ratio)
 Discuss Changes in life expectancy and changes in age / sex
distribution
 Discuss Changes in major causes of death Changes in age / sex
distribution
2
BURHAN UDDIN, Karachi

Introduction
 The epidemiologic transition describes changing patterns of
population age distributions, mortality, fertility, life expectancy,
and causes of death.
(McKeown, 2009, p. 19)
 The "epidemiologic transition theory" was first formulated in a
paper published in 1971.
(Omran, 2005, p.329)
 This theory provides description and explanation of the mortality
component of the "demographic transition"
 death rates
 birth rates
3

Epidemiologic Transition
A characteristic shift in the disease pattern of a population as
mortality falls during the demographic transition: acute, infectious
diseases are reduced, while chronic, degenerative diseases increase
in prominence, causing a gradual shift in the age pattern of
mortality from younger to older ages
(Omran 1970)
4

Epidemiologic Transition Theory
 Formulated by epidemiologist Abdel Omran in 1971.
 It comprises three stages characterized by fertility levels
and causes of death
1. The age of pestilence and famine
2. The age of receding pandemics
3. The age of chronic diseases

First Epidemiological Transition
 The First Epidemiological
Transition occurred 100
centuries ago when man
moved towards the
agricultural society.
 By eschewing the nomadic
lifestyle, people stayed in
one place and increased
their contact with human
(and animal) waste, and
contaminated their water
supplies. BURHAN UDDIN, Karachi 7

First Epidemiological Transition…
 And even the cultivation of
soil, and the clearing of land,
exposed people to insect
bites, bacteria, and parasites.
 As cities grew, and
exploration of the surrounding
world increased, man spread
deadly diseases in ever-
greater numbers.

First Epidemiological Transition…..
 This epidemiological transition was
described as
“the age pestilence and famine" .
 Epidemic, famines and wars
caused huge numbers of deaths.
 Infectious diseases were dominant,
causing high mortality rates,
especially among children.

First Epidemiological Transition….
 High levels of mortality and fertility.
 Crude Death Rate (CDR) is high and ranges from 30 to
over 50 deaths per 1,000 population.
 Infant mortality rate 200-300 deaths per 1,000 live
births.
 Life expectancy between 20-40 years.

Second Epidemiological Transition
 The Second Epidemiological
Transition began roughly 200
years ago, with the Industrial
revolution.
 While many of the existing
diseases brought forth during
the first transition certainly did
not go away, new-chronic, non-
infectious, degenerative
diseases – were added

 Increased economic growth led to a
sharp fall in deaths from infectious
diseases, and from malnutrition.
 This Improvement occurred before
effective medical treatment and was
due to impact of following
interventions:
 clean water
 sanitary sewage
 mosquito suppression (malaria/yellow
fever)
 increased food safety – refrigeration and
pasteurization
 increased pre & post-natal care

 This phase was described as
“age of receding pandemics” by Omran.
 It involved a reduction in the prevalence of infectious
diseases, and a fall in mortality rates.
 CDR reaches a level of less than 30 deaths per 1,000
population.
 IMR was 150 per 1,000 live births.
 As a consequence, life expectancy at birth climbed
rapidly from about 35 to 50 years.

 Finally, the introduction of modern healthcare and health
technologies, e.g.
 immunization programmes
 introduction of antibiotics
enabled the control and elimination of group of infectious diseases
such as Diphtheria, polio and smallpox.

Third Epidemiological Transition
 Began in the late 20th century.
 This phase was described as
 ‘The age of chronic diseases’
by Omran.
 In the third stage the elimination of
infectious diseases makes way for
chronic diseases among the elderly.
 The major causes of death are so-
called chronic degenerative and man-
made diseases such as cardiovascular
diseases, cancer, and diabetes.

 While improved healthcare means
that these are less lethal than
infectious diseases, they
nonetheless cause relatively high
levels of morbidity.
 Increasingly, health patterns depend
on social and cultural behaviour,
such as patterns of food
consumption and drinking
behaviour.

 Due to low levels of mortality and fertility, there is little
population growth.
 CDR stabilises at a level of less than 20 deaths per
1,000 population.
 By the end of the third stage, infant mortality reaches a
level of less than 25 deaths per 1,000 live births.
 When the health transition is at an advanced stage, life
expectancy may exceed 80 years.
 However, the prevalence of one or more diseases means
that such a long life also includes, on average, a
relatively long period of morbidity.

Population Pyramids
 A Population Pyramid also called an age pyramid or age
picture is a graphical illustration that shows the
distribution of various age groups in a population.
 Most often, a population pyramid consists of two back-
to-back bar graphs
 Population is plotted on the X-axis and age on the Y-axis
 One bar graph shows the males, while the other graph
shows females in a particular population

Conti…
 The ages are made up of five-year age groups (also called
cohorts).
 Males are shown on the left and females on the right.

Parts of a pop pyramid
Title
Y axis- Age
of people
Oldest people
on top
Youngest people
on bottom
X axis- # of people of a certain age
* Men are usually on the left side, women on the right.
* *

Conti…

 Population pyramid gives a clear picture of how a country
transitions from high fertility to low fertility rate.
 The population pyramid here indicates stage 3 on
the demographic transition.
 The broad base of the pyramid means the majority of
population lies between ages 0–14, which tells us that the
fertility rate of the country is high and above
population Sub-replacement fertility .
 There is a higher dependency ratio of younger population
over the working population.
 Moreover, there is lesser older population due to
shorter life expectancy which is around 60 years
24

Types of Pyramids
 Pyramid shapes differ from country to country, or within a
country, region to region.
 However, four general pyramid shapes, as determined by
fertility rates and mortality rates, have been noted.
1) Expansive
2) Stable growth
3) Stationary
4) Declining

1-Expansive (Outgoing)
 A broad base, indicating a
high proportion of
children, a rapid rate of
population growth and a
low proportion of older
people.
 The pyramid points
upward.
 Fertility is high so the
many children are born
replacing the parents.
26

2. Stable growth
 Slow Growth/Stable :
 A structure with bars
that even out and reflect
stable or slow growth
over a period.
 A even proportion of
elderly and children that
reduces in number as the
people become older.
 It has a general shape of
a pentagon.
27

3. Stationary
 Stationary
 A narrow base and
roughly equal numbers
in each age group,
narrowing off at the
older ages.
 The base and the
centre of the pyramid
make a box shape.
 In this case, fertility
equals mortality.
28

4. Declining
 This pyramid has a small
base suggesting a low
proportion of children to
many older people.
 The pyramid points
downward.
 Fertility is so low that the
number of children born
does NOT replace the
parents.

Population changes and Human Determinants of Transitions
Technological change
Alterations in the environment
Alterations in food type, availability,
production, preparation, and consumption
Alterations in patterns of energy
expenditure
Interplay of environmental factors and the
genetic pool of a community
30

Factors effecting population changes
 There are four factors that affect population change in a
country.
1) BIRTH RATE:
the number of live births per 1000 in a year
 Birth rates are affected by such factors as nutrition, fertility,
attitudes about abortion, labor value of children, government
policies, social value, the availability of contraception and
culture.
31

2) DEATH RATE
 The number of deaths per 1000 in a year
 Death rates are affected by disease, war, medical
technology, improved health care, transportation
development and nutrition.
3) IMMIGRATION
 The number of people moving into a country.
 Pull factors-characteristics of a place that attracts people to
it.
32

4) EMIGRATION
 The number of people leaving a country
 Push Factors-characteristics of a place that causes people
to leave.
 Refugees- people who are forced to leave their country
due to war, life-threatening discrimination, food shortage,
or natural disasters
33

Sex ratio
 Sex ratio is the demographic concept that measures the
proportion of males to females in a given population.
 It is usually measured as the number of males per 100
females.
 The ratio is expressed as in the form of 105:100, where in this
example there would be 105 males for every 100 females in a
population.
34

Cont….
 The average natural sex ratio for humans from birth is
approximately 105:100.
 Scientists are not sure why there are 105 males born for
every 100 females around the world.
 Today, sex-selective abortions are unfortunately common in
countries like India and China.
 The introduction of ultrasound machines throughout China
in the 1990s led to a sex ratio of up to 120:100 at birth due
to familial and cultural pressure to have one's only child as
a male.
35

Cont….
 In later life, the life expectancy of men tends to be
shorter than women and thus men die earlier in life.
 Thus, many countries have a very high proportion of
women to men in the over age 65 range...
 Russia – 45:100
 Seychelles – 46:100
 Belarus – 48:100
 Latvia – 49:100

'Dependency Ratio
 A measure showing the number of dependents (aged
0-14 and over the age of 65) to the total population
(aged 15-64). Also referred to as the "total
dependency ratio".



10 8 6 4 2 0 2 4 6 8 10
80 and over
79-75
74-70
69-65
64-60
59-55
54-50
49-45
44-40
39-35
34-30
29-25
24-20
19-15
14-10
9-5
4-0
Percentof Total Population
Age
Group
Age-Sex Pyramid of Afghanistan,
2010
Male Female
8 6 4 2 0 2 4 6 8
80 and over
79-75
74-70
69-65
64-60
59-55
54-50
49-45
44-40
39-35
34-30
29-25
24-20
19-15
14-10
9-5
4-0
Percentof Total Population
Age
Group
Age-Sex Pyramid of Pakistan,
2010
Male Female

Gordis: Epidemiology, 4th ed. 2008
Palmore,J.A,& Gardner,R.W. (1983) Measuring Mortality,
Fertility, and Natural Increase: A self teaching guide to
elementary measures. Honolulu.
Newell C. Methods and model in demography. Arnoled:
oxford press.
Hinde A. Demographic methods. John Willey & sons:
New York.

REFERENCES'
 Gordis: Epidemiology, 4th ed. 2008
 Palmore,J.A,& Gardner,R.W. (1983) Measuring
Mortality, Fertility, and Natural Increase: A self
teaching guide to elementary measures. Honolulu.
 Newell C. Methods and model in demography.
Arnoled: oxford press.
 Hinde A. Demographic methods. John Willey & sons:
New York.

UNIT V EPIDEMIOLOGICAL TRANSITIONS IN DISEASE PATTERNS.pdf

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