Theories of Disease Causation and Historical Perspectives
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THEORIES OF
DISEASE
CAUSATION
MS. SAMAH ALAGEEL
Community Health
CHS 212
Outline:
Definition of disease.
The gradual development of disease causation:
Miasma theory.
Germ theory.
Epidemiological models of disease.
Web of causation.
The theory of general susceptibility.
The socio-environmental approach.
Conclusion.
OPPOSITE TO
HEALTH
What is disease??
Definition of disease:
“A condition in which body function is impaired,
departure from a state of health, an alteration of
the human body interrupting the performance of
the vital functions.” - Webster.
Definition of disease: (Cont.)
“The condition of body or some part of organ of
body in which its functions are disrupted or
deranged” - Oxford English Dictionary
How disease is caused?
Before the rise of modern medicine, disease was
attributed to a variety of spiritual or mechanical
forces, including:
A punishment from God for a sinful behavior.
Weak moral character.
Witchcraft.
How disease is caused? (Cont.)
However, these disease causation interpretations were
challenged and changed as the theories of disease
causation was developed, changing people’s views of
diseases as related to specific agents and other
environmental factors.
How disease is caused? (Cont.)
Theories of disease causation:
o
Miasma theory.
o
Germ theory.
o
Epidemiological triangle.
o
Web of causation
o
The theory of general susceptibility.
o
The socio-environmental approach.
Miasma Theory
The word "miasma" comes from ancient Greek and
means "pollution".
Miasma was considered to be a poisonous vapor or
mist filled with particles from decomposed matter
(miasmata) that caused illnesses.
Miasma Theory (Cont.)
In the 1850s, miasma was used to explain the
spread of cholera in London and in Paris.
In China, miasma was thought to be caused by the
heat, moisture and the dead air in the Southern
Chinese mountains. They thought that insects’
waste polluted the air, water.
The miasma theory was consistent with
observations that disease was associated with poor
sanitation.
As a result of the miasma theory
The sanitary movement era
(The first half of the nineteenth century)
1.
Public health measure were concerned with
sanitation.
2.
Focus was on disease prevention (causes of
diseases in population) and the health needs of
poor population.
3.
The epidemiology were largely involved in
population-wide health improvement.
Germ theory
Health problems were
believed to be the product
of living organisms which
entered the body through
food, water, air or the bites
of insects or animals.
It was believed that each
disease has a single and a
specific cause (mono-causal
approach).
The result of the Germ Theory:
Researches were moved
from the community to
the laboratory and
concentrated on the
identification of agents for
a given disease.
Medical practice became
devoted to the destruction
or eradication of the agent
from individuals already
affected.
Epidemiological triangle
According to this theory, exposure to an agent does
not necessarily lead to disease.
It was believed that disease is the result of an
interaction between agent,
host and the environment.
Bacteria
Viruses
Fungi
Age
Sex
Health Behavior
Immunity
Genetic makeup
Air
Water
Sanitation
Noise
As a result of the epidemiological triangle theory:
It was believed that diseases can be prevented by
modifying factors which influence exposure and
susceptibility.
This is useful in understanding infectious disorders,
but less useful in dealing with chronic, degenerative
diseases such as heart diseases and diabetes. For
these disorders there is no specific agent that could
be identified against which individual and
population may be protected.
Web of causation
According to this concept, disorders are developed
through complex interaction of many factors.
These factors maybe biophysical, social or
psychological and may promote or inhibit the disease
at more than one point in the causal process.
Ultimately, they determine the level of disease in a
community.
Cause
Cause
Cause
Cause
Effect \ Disease
As a result of this theory:
Based on this theory, it is believed that prevention
offers a better prospects for health than cure, since
many of these factors can be modified.
Since several factors contributes to several diseases,
community efforts were shifted to factors modification
(prevention) rather than disease treatment.
Theory of general susceptibility
This theory is not concerned with identifying single
or multiple risk factors associated with specific
disorders.
It seeks to understand why some social groups seems
to be more susceptible to disease and death in
general.
This reflects an imperfectly understood general
susceptibility to health problems.
Examples:
Low social class
Lung
Cancer
Respiratory
disease
Cerebro-vascular
disease
Ischemic heart
diseases
Higher
rates
Examples (Cont.):
African American
Hypertension
Dementia
Stroke
Diabetes (NIDD)
Prostrate
cancer
Higher risk group
The socio-environmental approach
This approach is not so much concerned with the
causes of disease, rather it seeks to identify the broad
factors that make and keep people healthy .
It is concerned with the population rather than
individuals.
Factors that improve people’s health:
Based on the socio-environmental approach, five
broad factors that can be targeted in order to
improve population health :
The social and economic environment.
The physical environment.
Personal health practices.
Individual capacity and coping skills.
Health services.
As a result of this theory:
Health actions shifted from the individual to the
community as a whole.
Improving health requires political and regulatory
actions to modify social, economical and physical
environment.
Conclusion
As briefly described, it is clear that the role attributed
to the physical, social and psychological environment
increases as we have progressed from the germ theory
to socio-environmental models of health.
The idea of diseases causation have moved from one
specific etiology to a broad non-specific multi factors
that are seen to be associated with a variety of disease
outcomes and ultimately the health and wellbeing of
the population.
The actual causation of particular
forms of disease is in many cases
obscure, because of the limitations of
our present knowledge.
Now its time to do it yourself…
Lung cancer
Hypertension
Malnutrition
Obesity
Depression
Explore the evolution of disease causation theories from miasma theory to germ theory, epidemiological models, and the socio-environmental approach. Understand the definition of disease, its causes, and how ancient beliefs in spiritual or mechanical forces led to new scientific interpretations.
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Presentation Transcript
Community Health CHS 212 THEORIES OF DISEASE CAUSATION MS. SAMAH ALAGEEL
Outline: Definition of disease. The gradual development of disease causation: Miasma theory. Germ theory. Epidemiological models of disease. Web of causation. The theory of general susceptibility. The socio-environmental approach. Conclusion.
What is disease?? OPPOSITE TO HEALTH
Definition of disease: A condition in which body function is impaired, departure from a state of health, an alteration of the human body interrupting the performance of the vital functions. - Webster.
Definition of disease: (Cont.) The condition of body or some part of organ of body in which its functions are disrupted or deranged - Oxford English Dictionary
How disease is caused? Before the rise of modern medicine, disease was attributed to a variety of spiritual or mechanical forces, including: A punishment from God for a sinful behavior. Weak moral character. Witchcraft.
How disease is caused? (Cont.) However, these disease causation interpretations were challenged and changed as the theories of disease causation was developed, changing people s views of diseases as related to specific agents and other environmental factors.
How disease is caused? (Cont.) Theories of disease causation: o Miasma theory. o Germ theory. o Epidemiological triangle. o Web of causation o The theory of general susceptibility. o The socio-environmental approach.
Miasma Theory The word "miasma" comes from ancient Greek and means "pollution". Miasma was considered to be a poisonous vapor or mist filled with particles from decomposed matter (miasmata) that caused illnesses.
Miasma Theory (Cont.) In the 1850s, miasma was used to explain the spread of cholera in London and in Paris. In China, miasma was thought to be caused by the heat, moisture and the dead air in the Southern Chinese mountains. They thought that insects waste polluted the air, water. The miasma theory observations that disease was associated with poor sanitation. was consistent with
As a result of the miasma theory The sanitary movement era (The first half of the nineteenth century) Public sanitation. 2. Focus was on disease prevention (causes of diseases in population) and the health needs of poor population. 3. The epidemiology were population-wide health improvement. health measure were concerned with 1. largely involved in
Germ theory Health problems were believed to be the product of living organisms which entered the body through food, water, air or the bites of insects or animals. It was believed that each disease has a single and a specific cause (mono-causal approach).
The result of the Germ Theory: Researches were moved from the community to the laboratory and concentrated on the identification of agents for a given disease. Medical practice became devoted to the destruction or eradication of the agent from individuals already affected.
Epidemiological triangle According to this theory, exposure to an agent does not necessarily lead to disease. It was believed that disease is the result of an interaction between agent, host and the environment.
Health Behavior Immunity Sex Age Genetic makeup Noise Bacteria Air Viruses Water Fungi Sanitation
As a result of the epidemiological triangle theory: It was believed that diseases can be prevented by modifying factors which influence exposure and susceptibility. This is useful in understanding infectious disorders, but less useful in dealing with chronic, degenerative diseases such as heart diseases and diabetes. For these disorders there is no specific agent that could be identified against which individual and population may be protected.
Web of causation According to this concept, disorders are developed through complex interaction of many factors. These factors maybe biophysical, social or psychological and may promote or inhibit the disease at more than one point in the causal process. Ultimately, they determine the level of disease in a community.
Cause Cause Effect \ Disease Cause Cause
As a result of this theory: Based on this theory, it is believed that prevention offers a better prospects for health than cure, since many of these factors can be modified. Since several factors contributes to several diseases, community efforts were shifted to factors modification (prevention) rather than disease treatment.
Theory of general susceptibility This theory is not concerned with identifying single or multiple risk factors associated with specific disorders. It seeks to understand why some social groups seems to be more susceptible to disease and death in general. This reflects an imperfectly understood general susceptibility to health problems.
Examples: Low social class Higher rates Lung Cancer Ischemic heart diseases Respiratory disease Cerebro-vascular disease
Examples (Cont.): African American Higher risk group Diabetes (NIDD) Hypertension Stroke Dementia Prostrate cancer
The socio-environmental approach This approach is not so much concerned with the causes of disease, rather it seeks to identify the broad factors that make and keep people healthy . It is concerned with the population rather than individuals.
Factors that improve peoples health: Based on the socio-environmental approach, five broad factors that can be targeted in order to improve population health : The social and economic environment. The physical environment. Personal health practices. Individual capacity and coping skills. Health services.
As a result of this theory: Health actions shifted from the individual to the community as a whole. Improving health requires political and regulatory actions to modify social, economical and physical environment.
Conclusion As briefly described, it is clear that the role attributed to the physical, social and psychological environment increases as we have progressed from the germ theory to socio-environmental models of health. The idea of diseases causation have moved from one specific etiology to a broad non-specific multi factors that are seen to be associated with a variety of disease outcomes and ultimately the health and wellbeing of the population.
The actual causation of particular forms of disease is in many cases obscure, because of the limitations of our present knowledge.
Now its time to do it yourself Depression Hypertension Obesity Malnutrition Lung cancer
