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Epidemiological transition

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EPiDEMiOLOGiCAL TRANSiTiON 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
Transcript

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.

Small pox, Cholera, plague, influenza, and typhus all

became major scourges for humanity.

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

Second Epidemiological Transition

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

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.

Epidemiologic Transition

Mort

alit

y

Rate

s

CA

CHDNIDDM

Trauma

Infectious Diseases

Third Epidemiological Transition

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


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