concepts of disease

May 1, 2023 PUBLIC HEALTH DENTISTRY- SRI SAI COLLEGE OF DENTAL SURGERY

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GOOD MORNING

May 1, 2023 2PUBLIC HEALTH DENTISTRY- SRI SAI COLLEGE OF DENTAL

SURGERY

Concept of DiseasePresented by Dr. Hari prasad Gone

Guided by Dr.Monica Mam

May 1, 2023 PUBLIC HEALTH DENTISTRY- SRI SAI COLLEGE OF DENTAL SURGERY 3

contents• Definition of disease

• Distinction between disease, illness, sickness

• Concept of causation-theories

• Epidemiological triad

• Multifactorial causation

• Web of causation


• Natural history of disease

• Spectrum of disease

• Iceberg phenomenon of disease

• Conclusion

• References


by end of seminar You will be able answer• What is disease

• Why you need to study

• Why it occurs

• When it occurs

• How it progresses

• What is your role as epidemiologist


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• Disease the word itself has an negative vibe and recalls a memory of suffering.

• Earlier disease was viewed as an curse or punishment for sins committed by man i.e. it has its own fear factor.

• Later perceptions on disease were changed . It is now viewed as a channel to explore more crevices in understanding human body its capabilities, limitations, interactions etc.


Introduction

• Disease and health are relative components

• "Health is a state of complete physical, mental and social wellbeing and not merely an absence of disease or infirmity"- WHO 1948


The definitions of disease seem to have varied with the prevailing explanatory models of medicine.

Medicine has studied disease in terms of

Disturbance of bodily homeostasis (Hippocrates, Galenus),

Morphological changes in the internal organs (Morgagni),

Tissues (Bichat) or cells (Virchow),

The irritation of the organs and their reaction (Brown),


The invasion of the body of an external contagion (Koch) and genetic alterations.

Whereas ancient medicine defined disease as the disturbance of humoral homeostasis.

Medicine of the third millennium seeks to define disease in the language of microscopic or radiographic morphology, biochemistry and molecular biology.


Webster defined disease as • "a condition in which body health is impaired, a departure from a

state of health, an alteration of human body interrupting the performance of vital functions”

• The Oxford English Dictionary defines disease as condition of the body or some part or organ of the body in which its functions are disrupted or deranged".


• From an ecological point of view, disease is defined as maladjustment of human organism to the environment.

• From sociological point of view, disease is considered as a social phenomenon occurring in all societies.

• In simple words disease is -----.


Disease: medical aspects Sickness: social Illness: personal


• Disease • It can be described as physiological or psychological

dysfunction of the body(literally without ease- the opposite of ease- when something is wrong with bodily function)


Illness

• It is a subjective state of the person who feels aware of not being well.


Sickness

• It is a state of social dysfunction .

• It can be described as inability to perform his ‘social role’/a role that individual assumes when ill -- sickness role).


WHO has defined health but not disease,

because of the following limitations?

• Disease has got many shades(spectrum0

• Onset – acute or chronic

• Healthy outside infect others carriers


• The same pathogen - more than one disease (eg:streptococci).

• The same disease - more than one organism (e.g. diarrhoea).

• The course of the disease may be short or prolonged

• It is difficult to demarcate between normal and abnormal state as in hypertension, diabetes, mental illness, etc.


• The final outcome of the disease isvariable, i.e. recovery, disability or death.

• Thus disease is a complex concept which is used as general term but has more complex meaning and its exact definition to set limits is under constant debate.


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Why do you need to know about disease??


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Why does concept of disease matters? • Disease is a central notion to modern healthcare; it effects

society

• In order to decide who is entitled to treatment and to economic rights, who is to be exempted from social duties and who is morally accountable, and to decide what the subject matter of medical science is.


• Furthermore, a strictly, consistently and coherently defined concept of disease could help the health care system face its basic economical, social, epidemological and ethical challenges, and could clarify the goal and limit of medicine.


Theories of causation• They are categorised as

Old theories and

Modern theories


Old theories

• The supernatural theory of disease. (e.g. curse of God; an evils eye), the theory of humors, miasmatic theory of disease, the theory of spontaneous generation, etc. The Ayurveda ,chinese medicine etc----empirical causes

• (primitive ,religious ) biogenesis (Omne vivum ex vivo "all life from life")

https://en.wikipedia.org/wiki/Biogenesis

https://en.wikipedia.org/wiki/Omne_vivum_ex_vivo





Modern theories• Modern theories

• germ theory• multifactorial causation – socioeconomic, cultural,

genetic, psychological• epidemiological triad (tetrad)/ecological triad• Advanced epidemiological triad• web of causation


Germ theory

• Louis Pasteur demonstrated presence of bacteria in air.

• Robert Koch showed that anthrax was caused by bacteria.

• These discoveries shifted concept of disease causation from empirical causes (e.g., bad air) to microbes as the sole cause of disease.


• The concept of cause embodied in the germ theory of disease is generally referred to as a one-to one relationship between causal agent and disease. The disease model accordingly is

• Disease agent-------> Man-------> Disease• The germ theory of disease, though it was a revolutionary

concept, led many epidemiologists to take one-sided view of disease causation.


Limitations of Germ Theory • Why only some people suffer from the disease even after

exposure

• Why certain people carry pathogens but do not show manifestations of disease

• Why a disease would be epidemic sometimes

• It does not take into account the multi-factorial causation even in the diseases in which micro-organism is the “necessary cause”.


Epidemiological triad/ecological triad

Agent

EnvironmentHost

Time


Epidemiological triad

Agents• Biological• Physical• Chemical • Mechanical• Insufficiency or excess of factors, hormones, nutrients,

parts, structural defects, chromosomal factors, immunological factors

• Social


Epidemiological triad• Host

• Demographic• Biological – genetic, biochemical, immunological,

physio functions• Social and economic• Lifestyle


Epidemiological triad • Environment

• Physical, • Biological, • Psychosocial


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Theory of multifactorial causation Pettenkofer of Munich proposed this concept earlier to the germ

theory but the germ theory of disease overshadowed the multiple cause theory.

As a result of advances in public health, chemotherapy, antibiotics and vector control communicable diseases began to decline- only to be replaced by new types of diseases, the so called modern diseases of civilization. e.g. lung cancer, coronary heart disease, chronic bronchitis, mental illness, etc.

Lung cancer, coronary heart disease, chronic bronchitis, mental illness, etc. all of which cannot be explained by earlier theories.


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These diseases cannot be explained on the basis of the germ theory of disease nor can be prevented by the traditional methods of isolation, immunization or improvement in sanitation.

The realization began to dawn that the “single cause idea” was an oversimplification and that there are other etiological factors- social, economic, cultural, genetic and psychological which are equally important.

As already mentioned, tuberculosis is not merely due to tubercle bacilli; factors such as poverty, overcrowding and malnutrition contribute to its occurrence.


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For example,

excess fat intake, smoking, lack of physical exercise, and obesity are all the factors involved in the pathogenesis of Coronary Heart Disease.

Most of these factors are linked to lifestyle and human behaviour.

Medical men are looking "beyond the "germ theory" and the multi-

factorial causation concept came into existence.


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The term agent is replaced by causative factors which implies the need to identify multiple causes or etiological factors of disease, disability, injury or death.

Why do you need to know associated multiple factors??

The purpose of knowing multiple factors of the disease is to quantify and arrange them in priority sequence for modification or amelioration to prevent or control the disease.


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Advanced model of triangle of epidemiology

Risk factors and risk groups• Risk factors

• Modifiable, non-modifiable• Examples for CVD


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Risk groups

• Target groups

• Risk approach


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Web of causation

This model of disease causation was suggested by Mac Mahon and Pugh.

This model is ideally suited in the study of chronic disease, where the disease agent is often not known, but is the outcome of interaction of multiple factors.

The "web of causation" considers all the predisposing factors of any type and their complex interrelationship with each other


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Web of causation


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The web of causation does not imply that the disease cannot be controlled unless all the multiple causes or chains of causation or at least a number of them are appropriately controlled or removed.

Sometimes removal or elimination of just only one link or chain may be sufficient to control disease, provided that link is sufficiently important in the pathogenic process.

In a multifactorial event, therefore, individual factors are by no means all of equal weight.


Natural history of disease• The term Natural history of disease is a key concept in

epidemiology.

• It signifies the way in which a disease evolves over time from the earliest stage of its prepathogenesis phase to its termination as recovery, disability or death, in the absence of treatment or prevention.


Natural history of disease


Spectrum of diseaseLord Yama’s given spectrum of death


Iceberg phenomenon


Iceberg of disease


Iceberg phenomenon

May 1, 2023

PUBLIC HEALTH DENTISTRY- SRI SAI COLLEGE OF DENTAL SURGERY50

Finally what is our role??

What the physician sees in the hospital is just an "episode" in the natural history of disease.

The epidemiologist, by studying the natural history of disease in the community setting is in a unique position to fill the gaps in our knowledge about the natural history of disease.


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Do you know???


conclusion• Defining a disease is a complex on going debate an

adequate defintion explaining diffuse nature of disease is yet to be found.

• Concept of disease and its comprehension by us is everchanging since times immemorial from empirical causes to evidence based or supported causes. Understanding disease has progressed from studying clinical cases to susceptibles that too molecular and gene level.


• Man has altered his physical environment to reduce infectious diseases mortality to a great extent only to get them replaced by chronic or modern also called lifestyle diseases. Man today viewed as an “agent” of his own diseases. Today man lives long enough to get affected by chronic diseases unlike in earlier generations where mortality at younger age was more due to infectious diseases.


DENTAL PUBLIC HEALTH SIGNIFICANCE• The epidemiologist, by studying the natural history of

disease in the community setting is in a unique position to fill the gaps in our knowledge about the natural history of disease.

• KNOWLEDGE OF DISEASE HOW WHY WHAT WHENS aids in diagnosis prevention and management of various diseases at a community level.


References Preventive and social medicine 23rd edition- K.PARK

Textbook of preventive and community dentistry- soben peter

Community medicine with recent advances – A H Suryakantha

Complexity of disease

Term Lifestyle diseases have to be avoided

Concept of disease


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Vallagard S.Why the concept “ lifestyle diseases” should be avoided,

Scandinavian journal of public health , 2011 ; 39: 773-775.

Alexandar c, tsai , bridget f.O., Burns . Syndemics of psychological problems and HIV risk : A systematic review of empirical tests of the disease interaction concept , Social science & Medicine, 201 ;139 :26-35

ThankYou

concepts of disease

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