1. ASSOCIATION AND CAUSATION
KESHAVA PAVAN K
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2. INTRODUCTION
 Association is the concurrence of two variables more
often than would be expected by chance.
 Events are said to be associated when they occur
more frequently together than one would expect by
chance
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3. TYPES
 Spurious
 Indirect
 Direct
 One-to-one
 multifactorial
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4. SPURIOUS ASSOCIATION
 Appears due to improper comparison
 Observed association between a disease & suspected
factor may not be real.
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5. INDIRECT ASSOCIATION
 Statistical association between a character of interest
and a disease due to presence of another factor,
known or unknown, that is common to both the
factors.
Altitude
 Iodine deficiency
Endemic goitre
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6. DIRECT ASSOCIATION
 Between two attributes that are directly related to
each other.
 One-to-one causation: when disease is present, factor
must also be present. e.g., Hemolytic streptococci
causing tonsillitis, scarlet fever, erysipelas
 Multifactorial causation: alternative causative factors
acting independently. e.g., lung cancer being caused
by smoking, air pollutants.
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7. CRITERIA FOR JUDGING CAUSALITY
Bradford Hill report, 1964
 Temporal association
 Strength of association
 Specificity of association
 Consistency of association
 Biological plausability
 Coherence of association
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8. TEMPORAL ASSOCIATION
 Causal attribute must precede the disease or
unfavourable outcome
 Exposure to factor must have occurred before the
disease developed
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9. STRENGTH OF ASSOCIATION
 If the association is strong or weak
 With increased level of exposure to risk factor,
incidence of disease increases.
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10. SPECIFICITY OF ASSOCIATION
 One to one relation between cause and effect
 Weakest of the criteria
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11. CONSISTENCY OF ASSOCIATION
 Occurrence of association at some other time & place
repeatedly.
 If a relationship is causal, findings should be
consistent with other data.
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12. BIOLOGICAL PLAUSABILITY
 Association must be consistent with other knowledge
like mechanism of action, evidence from animal
experiments etc.
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13. COHERENCE OF ASSOCIATION
 Causal significance of an association is its unity with
known facts that are thought to be related.
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14. THANK YOU
 THANK YOU for reading my presentation.
 If you have any doubts or interesting cases in any subject of
medicine, I will be delighted if you share at
keshavapavan533@gmail.com
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