Ram Rangsin, MD MPH DrPH

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???????????????????????
Ram Rangsin, MD MPH DrPH Department of Military
and Community Medicine Phramongkutklao College of
Medicine, THAILAND
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????????????? 2 ?????

• ????????????
• ????????????????????????????????
• ??????????????????????????????????????????????????
  ????????
• ???????????????????????????????????
• ??????????????????????????????????????????????????
  ??
• ??????????????????????????????????????????????????
  ??????????????????????????????

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????????????? 2 ????? ??????

• ???????????? (?????????????) ??????????
• ??????? Prevalence
• ????????? Incidence
• ???????????????????????????????????
  (??????????????????????) ?????????????
• Relative Risk gt Cohort Study
• Odds Ratio gt Case Control Study
• Prevalence Rate Ratio gt Cross Sectional
  Study

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Classification epidemiological study
???????? (Experiment) (exposure given by
researcher)
????????? (Observation) (natural exposure)
??????????????? Descriptive (???????????????????
??)
?????????????????? Analytic (??????????????????)
Cross sectional Case control
Cohort
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?????????????????????????????????????
Case report a dengue shock case Case series 3
dengue shock cases Cross sectional study a
hypertension survey Cross sectional study HT
vs Salt consumption Case control study HT vs
Salt consumption Cohort study HT vs Salt
consumption Clinical trial Beta blocker vs
Hypertension
Descriptive
Analytic
Experiment
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??????????????????
???????????????? ?? 3 ???? Time When did the
disease occur? Place Where did the cases
arise? Person Who was attacked by the disease?
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??????????????????
???????
?????? ????????????
???????
???????
?????????????????????????????
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???????????????????????
Non Cases Factor A
?????????????????????? ??????????
Cases Factor A
???????????????????????????????????????
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?????????????????????????????????????????????
Cause ??????
Effect ??

• RISK FACTOR (????????????)
• Cigarette

DISEASE (??????????) Lung Cancer
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?????????????????????

• Cross sectional Study
• (??????????, ????????)
• Case Control Study
• Cohort Study

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Cross - sectional Study
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A Survey on Hypertension
Hanoi
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???????????????????????????????????????

• The Health Department of Hanoi City in 2000
• 1,000,000 Hanoi population
• ????????
• ???????????? Cholesterol
• ???????????????

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???????????????????????????????????????

• 60,000 hypertension
• 200,000 high blood cholesterol
• Prevalence of HT ?

60,000/1,000,000 6
?????????????????????????????? ?????????????????
???????
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???????????????????????????????????????
ID
Age
Sex
Hyper-
High
tension
Chol
1
18
M
No
Yes
2
36
M
No
No
3
50
F
Yes
Yes
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???????????????????????????????????????
Defined Population
Gather Data on Exposure Disease
Exposed Have disease
Exposed No disease
Not Exposed Have disease
Not Exposed No disease
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???????????????????????????????????????
Disease
No Disease
a
b
Exposed
c
d
Not Exposed
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???????????????????????????????????????
Hyper- tension
No HT
20,000
180,000
High Chol.
200,000
40,000
760,000
Normal Chol.
800,000
1,000,000
940,000
60,000,
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???????????????????????????????????????

• High Cholesterol
• HT Prevalence Rate 20,000 / 200,000 10
• Normal Cholesterol
• HT Prevalence Rate 40,000 / 800,000 5
• Prevalence Rate Ratio 10 / 5 2

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Prevalence Rate Ratio

• ????????? Relative Risk ???????????
• ??????????
• Prevalence Rate Ratio 10 / 5 2
• ???????????? high cholesterol ????????????
• ????????????????????????????????????????
• high cholesterol ???? 2 ????

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Prevalence

• Dynamic stage
• the increasing by new cases,
• the decreasing by deaths and cures
• Prevalence Incidence x Duration

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• ?????? prevalence rate ratio ?????????????
  ??? relative risk
  ??????????
• ?????????????????????????????????????????????
  ??????????????????????????????????????
  ??????????????????????????
• ??????????????????????????????????? Case
  control ???? cohort studies
• II. ?????????????????? ??????????????????????????
  

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Cross - sectional Study

• ???????????????? (HT) ????????????????? (Chol.
  level) ??????? ? ?????????????????
• ????????????????????????????????????
• ?? Cross sectional Study ???????????????????????
  ?? ?????????????????????
• ??????????????????????????????????????????????????

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Cross - sectional Study

• ????????????? ?????????
• ??????????????????????????????????????????????????
  ????????????????????????????????
• ????????????????????????????????????????????
• ???????????????????????????????????????????????

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Case control Study
Non Cases Factor A
Cases Factor A
Cases Factor A
Non Cases Factor A
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Case Control Study
????????????????????????????????????????????
?????????????????????????????? ???????????????????
????????????? ???????????????????????????????????
?????????????????????????????? ??????? 2
????? (Epidemiology in Medicine)

• ???????
• ??????????????????????????????????????????????????
  ???????

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??????????? Case control Study

• ..it begins with people with the disease (cases)
  
• and compares them to people without the
  disease
• (controls).
• Source Gordis, page 142.

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Design for a case control Study
No Disease
Disease
Exposed
Not Exposed
Exposed
Not Exposed
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Steps

• ???????? Cases identification
• ????????????????? Controls
• ????????????????????????? exposure
  ??????? ??????? cases ??? controls
• ??????????? exposure status ??????? 2 ?????
• ??????? ODDS RATIO

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Design of Case Control Study
Time
Direction of inquiry
Exposed
Cases (Diseased)
Population
Not exposed
Exposed
Controls (Not diseased)
Not exposed
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???????? ?????????? (Controls)

• 1 1
• ?????????? Control ? Increase in Odds Ratio
• ????????????? 1 4

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Case Control Study

• 50 Cases of Lung Cancer (CA Lung)
• 50 Non lung cancer patients
• Find an association Smoking VS CA Lung

ID Age Sex Case or Control Smoke 1 18
M Case Control Yes 2 36 M Case
Control No 3 50 F Case Control
Yes 4 41 M Case Control No
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Controls
Cases
Lung Cancer 50 cases
NO Lung Cancer 50 cases
Exposed
Unexposed
Exposed
Unexposed
Smoke 45
Not Smoke 5
Smoke 15
Not Smoke 35
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CA Lung
No CA
Smoke
45
15
Case Control Study
Not smoke
5
35

• Odds of Smoking among CA Lung cases 45/5
• Odds of Smoking among Control 15/35
• Odds ratio 45/5 21
• ?????????????????????????? Lung Cancer
  ??????????????????? 21 ????

15/35
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Odds Ratio
Case
Control
Exposed
A
B
D
C
Not Exposed
Odds Ratio AD BC
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Measurement of Associations

• Cross sectional Point Prevalence Rate Ratio
• Case Control Odds Ratio
• Cohort Relative Risk

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Case Control Study

• Comparison between
• a group of persons with a disease -- CASES
• VS
• a group of persons without the disease --
  Controls

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Conducting a case control study

• You are interested in a group of patients with
  Coronary Artery Heart Disease N200
• You found that more than a half of the cases with
  Coronary Artery Heart Disease in your clinic were
  smokers
• Please conduct a case control to find association
  between smoking and liver cell cancer

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Cohort Study

• ??????????????????????????????????????????????????
  ????????????????????????????????
• ??????????????????????????
• ??????????????????????????????

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?????????????????????????????????????????????
Cause ??????
Effect ??

• RISK FACTOR (????????????)
• Cigarette

DISEASE (??????????) Lung Cancer
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Cause
Effect
Factors
Disease
Case Control
Factors
Disease
Cohort
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Factors
Disease
Exposed
Not Exposed
???????
??????????
???????
??????????
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Persons without the disease !!!!
1970
Not Exposed
Exposed
Not Smoke 500 persons
Smoke 500 persons
Disease
No Disease
Disease
No Disease
Lung Cancer 45
Lung Cancer 1
No Lung Cancer 455
No Lung Cancer 499
2001
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CA Lung
No CA
Smoke
500
45
455
499
Not smoke
1
500

• Incidence of Smoker who develop Lung Cancer
  45/500
• Incidence of Non -Smoker whodevelop Lung Cancer
  1/500
• Relative Risk of smoking for Lung Cancer 45
  
• ?????????????????????????????????????????????????
  ???????? 45 ????

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Relative Risk
CA Lung
No CA
Smoke
AB
A
B
D
CD
C
Not smoke
Relative Risk A/AB
C/CD
46
CA Lung
No CA
500
45
455
Smoke
Cohort Study
Not smoke
500
1
499
CA Lung
No CA
Smoke
45
15
Case Control Study
Not smoke
35
5

• Do not have incidence in exposed incidence in
  non exposed
• Cannot calculate the RR directly

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Cohort Study
Comparison between a group of persons with a
factor -- Exposed VS a group of persons without
the factor -- Non-exposed

• When we are conducting a cohort study,
• We are dealing with INCIDENCE.

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Conducting a Cohort Study

• Selecting a group of people without the disease
• Defining the Exposed group
• Defining the Non-exposed group
• Evaluate the disease outcome among both Exposed
  and Non - exposed
• Calculating Relative Risk
• You are interested in the association between
  blood cholesterol level and coronary artery heart
  disease
• Please conduct a cohort study to verify the
  association