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EPiDEMiOLOGiCALTRANSiTiON
Dr. Manju
JR, Community Medicine
PGIMS, Rohtak
Any major shift in patterns of disease or
causes of death that affects the level and
character of mortality in a population
Contents
Health transition
Demographic transition
Epidemiological transition
Three stages of epidemiological transition
Exception and Implication of epidemiological transition
Hybristic Stages
Future stages of epidemiological transition
Epidemiological transition in developed and developing countries
Epidemiological transition models
Critics
Conclusion
The Health Transition
Health transition: the shifts that have taken place in the
patterns and causes of death.
The health transition has been covered by two separate
terms:
Demographic transition
Epidemiological transition
Demographic Transition
A change in the population dynamics of a country as it
moves from
HIGH FERTILITY AND MORTALITY RATES
LOW FERTILITY AND MORTALITY RATES
Demographic Transition Model- is highly predictive for most countries
Crude birth/death rate highFragile, but stable, population
Lower death ratesnot accompanied by a parallel reduction in birth rateNatural increase very high
Crude birth rate finally fallsPopulation growth is slow
Crude birth/death rates lowPopulation stablePopulations aging
improved agriculture and
medicine
Attitudes change &
Higher standards of
living/education
PHASE 1PHASE 2PHASE 3PHASE 4
This model is based on the interpretation of demographic history
developed in 1929 by the American demographer Warren Thompson .
Demographic Transition
DEVELOPED VS. DEVELOPING NATIONS
All industrialized nations have gone through these phases of demographic transition.
The developing nations have completed Phase I and are currently in Phase II - a phase of explosive rates of natural increase.
Countries in western Europe took roughly 200 years to complete their transitions.
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)
Demographic and
Epidemiologic transition
Economic,
social &
environ
mental
changes
public
sanitation,
housing,
health care
nutrition
technology
for health
care
mortality
( infant mortality)
life expectancy
fertility
Increasing
aging
population
persons at
risk of
developing
NCDs
levels of RF:
fat, calories, tobacco,
sedentary habits
Industrialization
& urbanization
NCD infectious
diseases
per cap. income,
wealth
IUMSP-GCT
Epidemiologic Transition Theory
Formulated by epidemiologist Abdel Omran in 1971.
It comprises three stages characterized by fertilitylevels and causes of death
1. The age of pestilence and famine
2. The age of receding pandemics
3. The age of chronic diseases
Age of pestilence and
famine
Age of receding pandemics
Age of chronic
diseases
Poor use of
ecological resources
and lack of social and
economic capital
Increased economic growth
improves use of ecological
resources and provides
basic social services
Improved medical
care and social
determinants
influences health
Life
expectancy
Time
hHealth
Health
Healt
h
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.
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 transitionwas described as
“the age pestilence and famine" .
Epidemic, famines and warscaused huge numbers of deaths.
Infectious diseases were dominant, causing high mortality rates, especially among children.
First Epidemiological Transition…
The domestication of animals
brought other disease vectors in
close contact with humans.
Q Fever, Anthrax, tuberculosis
gained access to human hosts.
While increasing food security
and nutrition, this transition also
introduced several significant
disease factors.
First Epidemiological Transition….
Small pox : 12,000 Years of
Terror
It first appeared in agricultural
settlements in north-eastern
Africa around 10,000 B.C.
Egyptian merchants spread it
from Africa to India.
In Europe, near the end of the
eighteenth century, the disease
accounted for nearly 400,000
deaths each year.
First Epidemiological Transition….
Of those surviving, one-third were blinded.
The worldwide death toll was staggering and continued well into the twentieth century, where mortality has been estimated at 300 to 500 million.
First Epidemiological Transition…
Plague – The Black Death.
The first recorded case of the plague
was in China in 224 B.C.
But the most significant outbreak was
in Europe in the mid-fourteenth century.
Over a five-year period from 1347 to
1352, 25 million people died.
One-third to one-half of the
European population was wiped out
!!!!!!
First Epidemiological Transition
Cholera The major cholera pandemics
are generally listed as:
First: 1817-1823,
Second: 1829-1851,
Third: 1852-1859,
Fourth: 1863-1879,
Fifth: 1881-1896,
Sixth: 1899-1923,
Seventh: 1961- 1970,
First Epidemiological Transition….
High levels of mortality and fertility.
Crude Death Rate (CDR) is high and ranges from 30 toover 50 deaths per 1,000 population.
Infant mortality rate 200-300 deaths per 1,000 livebirths.
Life expectancy between 20-40 years.
First Epidemiological Transition….
The provision of basic ecological resources, i.e. food andfresh water, was inadequate.
There was lack of sufficient infrastructure for mostservices.
Population growth, improvements in health, andadvances in socio-economic development were alllimited by the local carrying capacity of the environment.
First Epidemiological Transition…..
In this stage, women of
childbearing age also
faced considerable risks
due to the complications
associated with
pregnancy and childbirth.
Some developing
countries are still in this
stage.
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 to the
mix.
Second Epidemiological Transition
This phase was described as
“age of receding pandemics” by Omran.
It involved a reduction in the prevalence of infectiousdiseases, and a fall in mortality rates.
CDR reaches a level of less than 30 deaths per 1,000population.
IMR was 150 per 1,000 live births.
As a consequence, life expectancy at birth climbedrapidly from about 35 to 50 years.
Second Epidemiological Transition
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/yellowfever)
increased food safety – refrigeration andpasteurization
increased pre & post-natal care
Second Epidemiological Transition
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.
Second Epidemiological Transition
Technology also brought with it
smokestack industries, chemical
toxins, working indoors, stress,
greater access to less `healthful’
food; beside advances in medicine
and sanitation.
And with this second transition we’ve
seen rises in allergies, asthma,
autoimmune disorders, and sexually
transmitted diseases as well.
Second Epidemiological Transition
As fertility rates were high, population was growingrapidly at this stage of the health transition. Withoutmoving to the next stage, the carrying capacity of thelocal ecosystem may be exceeded.
As population and ecological pressures increased, foodand water became scarcer, and the lack of ecologicaland social resources may cause economicdevelopment to stagnate.
If there is a surplus of available resources, thetransition may be accelerated, but if they are lacking, thetransition may slow, or even stagnate in this phase.
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.
Third Epidemiological Transition
While improved healthcare meansthat these are less lethal thaninfectious diseases, theynonetheless cause relatively highlevels of morbidity.
Increasingly, health patterns dependon social and cultural behaviour,such as patterns of foodconsumption and drinkingbehaviour.
Third Epidemiological Transition
Due to low levels of mortality and fertility, there islittle population growth.
CDR stabilises at a level of less than 20 deaths per1,000 population.
By the end of the third stage, infant mortality reaches alevel of less than 25 deaths per 1,000 live births.
When the health transition is at an advanced stage, lifeexpectancy may exceed 80 years.
However, the prevalence of one or more diseasesmeans that such a long life also includes, on average, arelatively long period of morbidity.
Third Epidemiological Transition
This stage occurs at different rates in different nations: in both developed and developing countries, mortality
rates are driven by socially determined factors;
in developed nations they are also driven by medicaltechnology.
It becomes necessary to ensure sufficient social andhealth-care investment for all age groups.
At the same time, there is increased demand forhealthcare related to the diseases of older people.
Aging populations
1950 1975 2000 2025 Increase (fold)
1950-2025
Brazil 2 6 14 32 15
Mexico 1 3 7 18 13
Nigeria 1 3 6 16 12
Indonesia 4 7 15 31 8
China 42 74 135 284 7
Bangladesh 3 3 7 17 6
Japan 6 13 26 33 6
India 32 30 66 146 5
USSR 16 34 54 71 4
USA 19 32 40 67 4
Italy 6 10 14 16 3
Germany 7 12 13 15 2
trends in number of persons (millions) aged 60
Exceptions
Though the struggle against infectious diseases, especially
tropical diseases, was at first successful, some countries,
mainly in Africa, were unable to reach a pace of
progress sufficient to reduce the gap separating them
from developed countries.
The arrival of AIDS often caused severe reversals and
towards the end of the 1980s, life expectancy levels
suddenly dropped.
Implications of Epidemiological
Transition
The epidemiologic transition have given rise to as many problems which include:
nuclearization of the family
the destruction of group cohesion
rise in mental illness
crime, delinquency
drug dependency which boost the demand/psychiatric help
alarming rise in medical costs
Hybristic Stage
Rogers and Hackenberg (1987) felt that the original theory
lacked reference to violent and accidental deaths and
deaths due to behavioural causes.
They proposed a fourth stage that they called the
hybristic stage.
The term ‘hybris’ refers to excessive self-confidence or a
belief of invincibility.
During the hybristic stage, morbidity and mortality are
affected by man-made diseases, individual behaviours,
and potentially destructive lifestyles.
Hybristic Stage
Rogers and Hackenberg (1987) further remarked that while
most environmentally-based infectious diseases are
eradicated during the hybristic stage, some infectious
diseases are increasing in importance due to individual
lifestyles and man-made causes.
A well-known example of such an infectious disease is
HIV/AIDS.
Future stages of the epidemiological transition
Martens (2002) described the developments in thehealth status of populations according to three potentialfuture 'ages‘ :
4. “the age of emerging infectious diseases”
5. “the age of medical technology”
6. “the age of sustained health”
These stages are imaginary (although some features arealready recognizable in some countries) and are notsharply delineated- there is always a continuum.
Health
Health
Health
Age of sustaining health
Age of medical
technology
Age of emerging infectious diseases
The age of emerging infectious diseases
In this stage, the emergence of new infectious diseases or the re-emergence of 'old' ones will have a significant impact on health.
A number of factors will influence this development: travel and trade
microbiological resistance
human behaviour
breakdowns in health systems
increased pressure on the environment
The age of emerging infectious diseases
Social, political and economic factors that cause the movement of people will increase contact between people and microbes.
Environmental changes caused by human activity (for example, dam and road building, deforestation, irrigation, and, at the global level, climate change) will all contribute to the further spread of disease.
The overuse of antibiotics and insecticides,combined with inadequate or deteriorating publichealth infrastructures will hamper or delay responsesto increasing disease threats.
As a result, infectious diseases will increasedrastically, and life expectancy will fall.
The age of emerging infectious diseases
Ill health will lead to lower levels of economic activity,and poor countries will be caught in a downwardspiral of depressed incomes and bad health.
Control of infectious diseases will be hampered bypolitical and financial obstacles, and by an inability touse existing technologies.
The age of emerging infectious diseases
The age of medical technology
To a large extent, increased health risks caused by changes in life-style and environmental changes will be offset by increased economic growth and technology improvements in the age of medical technology.
If there is no long-term, sustainable economic development, increased environmental pressure and social imbalance may propel poor societies into the age of emerging infectious diseases.
The age of sustained health
In the age of sustained health, investments in social services will lead to a sharp reduction in life-style related diseases, and most environmentally related infectious diseases will be eradicated.
Health policies will be designed to improve the health status of a population in such a way that the health of future generations is not compromised by, for example, the depletion of resources needed by future generations.
The age of sustained health
Although there is only a minimal chance that infections will emerge, improved worldwide surveillance and monitoring systems will mean that any outbreak is properly dealt with.
Despite the ageing of the world population, health systems will be well adjusted to an older population.
Furthermore, disparities in health between rich and poor countries will eventually disappear.
Epidemiological Transition – Developed Countries
Currently, most developed countries are in the third stage of the health transition:
fertility rates are low
causes of diseases and deaths have shifted from infectious to chronic diseases.
Epidemiological Transition – Developed Countries
All developed countries in Europe, North America andAsia are seen as having arrived in the latter stage of thehealth transition in the 1970s, although there werelarge differences with regard to timing, particularly inthe onset of the decline in fertility.
In these countries, declining fertility rates andincreased life expectancy have led to the ageing, orso-called 'greying', of the population.
Epidemiological Transition –Developing Countries
The health situation indeveloping countriesvaries greatly from onecountry to another.
In most, there is still very low life expectancy; this is due largely to malnutrition and the lack of safe drinking water, which are compounded by poor healthcare facilities.
Epidemiological Transition –Developing Countries
In other countries, particularly in Asia and Latin America,chronic diseases have now become more importantthan infectious diseases.
In countries such as China and Thailand fertility ratesare very low; in others they are very high.
Due to sub-national differences of an economic, social orecological nature, there may also be large differenceswithin a single country.
Epidemiological Transition –Developing Countries
It is widely believed that, with increasing economic growth, developing countries will follow the same pattern of health transition as Europe and North America.
However, there is now evidence that the poorest in developing countries will not 'trade' infectious diseases for chronic diseases; instead, they face a triple burden of communicable disease, non-communicable disease and socio-behavioural illness.
< 20th/Early 20th Century 1940-1960/70 1960/70-2050+
TRIPLE HEALTH
BURDENUnfinished old set
Communicable disease
Reproductive morbidity
Nutritional deficiency
Rapid population growth
Rising new set
Cardiovascular disease
Malignancy and diabetes
Stress (depression)
Ageing and diseases of the elderly
Accidents (traffic, work)
Emerging and resurgent diseases
Lagging health care
Health systems and medical
training ill-suited for the rising
chronic and continuing acute
diseases plus long-term care for
the aged, the disabled and the
mentally ill.
Old set of morbidity -Communicable disease
* epidemics
* endemic
-Reproductive morbidity
and mortality
- Nutritional deficiency
-Poor sanitation and
housing
-Poor personal hygiene
-High child mortality
-High disability Adjusted
Life years Lost (DALYS)
due to early death
-Poverty
Transition
Rapid change
since mid 20th
Century
Recession of
epidemics
Preventable disease
burdenLE 30 30-45 45-70 +
Transition Stages in the developing Countries
Transition
Although improvements in health may take place worldwide, differences in health status between the developing and developed world will to some extent remain, regardless of the future development path.
The processes of globalization in today's world that include socio-economic change, demographic change and global environmental change, oblige us to broaden our conception of the determinants of population health.
Epidemiological Transition –Developing Countries
Epidemiological Transition model
Countries and regions have shown differences in passing
through the above-mentioned stages , with regard to
timing, pace, and underlying mechanisms.
Therefore, Omran (1971, 1982) proposed several basic
models of the epidemiologic transition.
Initially, he proposed three models, but later added a fourth
variant.
The Classical Model of Epidemiological Transition
In Western European countries.
The mortality pattern follows three stages.
A pre-industrial age of pestilence and famine generates a
cyclical population growth with frequent peaks in mortality
is followed by an intermediate stage of receding pandemics
in the middle or later part of the 19th Century giving way to
a gradual mortality decline.
A stage of degenerative and man made diseases in
the 20th Century corresponds to more precipitous declines.
The Classical Model of Epidemiological Transition
Economic factors (improvements in standards of living
and in nutrition in the 19th Century) were the primary
determinants of the classical transition, but were later
augmented in the 20th Century by sanitary
improvements, followed by medical and public health
progress.
The Accelerated Model
Observed in Japan and Eastern Europe.
The transition follows a similar pattern as the Classical
Model, but mortality decline started later and reached the
low level in a shorter period of time.
The changes were based on general social improvements
(for example in nutrition) as well as sanitary and medical
advances.
The Delayed Epidemiological Transition
most countries in Africa, Latin America, and Asia.
Mortality drops in these countries have mainly been
achieved by the application of modern medical technology.
Though initially mortality decline was fast, it slowed down
after the 1960s, especially in terms of infant and child
mortality.
The Epidemiological Transition closely parallels the
demographic transition and Industrial Revolution and is
therefore followed by a population explosion and by
sustained economic growth.
Transitional Variant Of The Delayed Model
This model depicts the transition in a number of
developing countries such as Taiwan, South Korea,
Singapore, Hong Kong, Sri Lanka, Mauritius, and
Jamaica.
In these countries, the rapid decline in mortality in the
1940s was comparable to that in countries matching the
delayed model.
However, the decline did not slacken to the same
extent.
Protracted-polarised Model
Suggested by Frenk, Bobadilla and colleagues (Frenk et al.
1989a, 1989b; Bobadilla et al. 1993)
This variant of the transition reflects the experiences of
some large middle-income countries such as Mexico.
The transition in these countries is to an extent
characterised by a relatively fast mortality decline that
started in the 20th century.
First of all, incidences of non communicable disease
increase before infectious diseases are fully brought under
control.
Protracted-polarised Model
This results in a so-called overlap of eras.
Further, some epidemic diseases that were controlled or
even eradicated re-emerge and lead to a counter
transition.
For instance, malaria, dengue fever, and cholera have re-
emerged in Mexico (Bobadilla et al. 1993).
Protracted-polarised Model
Lastly, unequal distributions of wealth and health services lead to increasing differences and widening gaps between social classes and between geographical regions
This process has been described as epidemiologic polarisation.
Examples of countries with important differences in mortality between geographic regions include Mexico and India.
CRiTiCS
Mackenbach (1994) limited his comments to the Western
model of the transition. He argues that the concept of the
epidemiologic transition is ill-defined and ambiguous.
In his argument, he focuses in particular on the difficulties
related to the identification and location in time of both the
beginning and the end of the transition.
Frenk et al. and Smallman-Raynor and Phillips put their
emphasis on the notion of reversibility and warn against
the assumptions of an unidirectional sequence and
uninterrupted progression.
From this perspective, the re-emergence of infectious and
parasitic diseases in developed countries would not
indicate a fifth stage but rather a possible counter-
transition.
CRiTiCS
By presenting their protracted-polarised model, Frenk,
Bobadilla and colleagues challenged the notion that “all
countries eventually pass through the same stages of the
transition, and that in each stage there is one dominant
pattern of morbidity and mortality”.
They tried to overcome this weakness in the transition
theory by introducing the concepts of counter transition,
overlap of eras, and epidemiologic polarisation.
CRiTiCS
Gaylin and Kates (1997) feel that the generalisability of the
epidemiologic transition theory may be undermined by the large
differences in mortality trends among population subgroups.
As a result, they argue for “the need to ‘particularise’ the focus
of the epidemiologic transition on population subgroups”.
In addition, they argue that the epidemiologic transition theory
suggests “a level of control of infectious diseases that has not
been achieved among certain subgroups and, in some cases,
entire populations”.
In other words, the theory is believed to have overestimated the
decline in infectious diseases as a cause of death.
CRiTiCS
Conclusion
Nevertheless, it is generally believed that the epidemiologic
transition theory presents a broad conceptual framework
that is useful for the study of global trends in disease and
mortality.
“the epidemiologic transition theory provides a potentially
powerful framework for the study of disease and mortality
in populations, especially for the study of historical and
international variations”. Mackenbach (1994)
Conclusion
This framework can be used to speculate on the possible
consequences of future changes in countries that have not
yet completed the epidemiologic transition.
These perceptions suggest what is perhaps the best way
to view the ‘epidemiologic transition’: not as a theory, but
rather as a framework or perspective.
References
Early life changes e-book.
National institute of demography, Paris, France.
Lecture by Dr. SC Mathur