concept of disease causation
DESCRIPTION
I MBBS class - basic concepts in community medicineTRANSCRIPT
Concept of disease
Dr. Rizwan S A, M.D.,Assistant Professor,
Department of Community Medicine,VMCH&RI, Madurai.
24.10.2014
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Outline
• Definition of disease– Distinction between disease, illness, sickness
• Spectrum of disease• Iceberg phenomenon• Theories of causation• Natural history of disease
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Spectrum of disease
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Iceberg phenomenon – 1/2
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Iceberg phenomenon – 2/2
1 Diseased, diagnosed & controlled
2 Diagnosed, uncontrolled
3 Undiagnosed or wronglydiagnosed disease
4 Risk factors for disease
5 Free of risk factors
Diagnosed disease
Undiagnosed orwrongly diagnosed disease
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Theories of causation
• Old theories• Modern theories– germ theory– multifactorial causation – socioeconomic, cultural,
genetic, psychological– epidemiological triad (tetrad) – web of causation– wheel of causation
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Epidemiological triad/tetrad – 1/4
Agent
EnvironmentHost
Time
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Epidemiological triad – 2/4
• Agents– Biological– Physical– Chemical – Mechanical– Insufficiency or excess of factors, hormones,
nutrients, parts, structural defects, chromosomal factors, immunological factors
– Social
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Epidemiological triad – 3/4
• Host– Demographic– Biological – genetic, biochemical, immunological,
physio functions– Social and economic– Lifestyle
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Epidemiological triad – 4/4
• Environment– Physical, – Biological, – Psychosocial
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Risk factors and risk groups
• Risk factors– Modifiable, non-modifiable– Examples for CVD
• Risk groups– Target groups– Risk approach
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Web of causation
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Wheel of causation
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Natural history of disease
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Example - TB
• Agent – types, sources, communicability• Host – age, sex, genetics, nutrition, immunity• Environment – urban slum, rural,
overcrowding, poor ventilation• Other social factors – ignorance, stigma,
health facilities, health habits, beliefs and customs
Thank You