Basic Epidemiology

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Basic Epidemiology

• Payman Salamati ,MD,MPH,
• Assistant Professor of community Medicine
• Tehran University of Medical Sciences
• 1387

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

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• 
  ????? ????? ???? ?????
  
• (crude mortality rate) ????? ??? ???
  x 1000
• ????? ?? ??? ???
  
  
• 
  
  
• ????? ??? ?? ?? ???? ??? ? ???? ???? ?? ???? ??
  ?? ????
  
  
• ????? ??? ??????? ???-????
  
  x 10n
• (age sex specific death rate) ????? ??
  ???? ??? ? ???? ???? ?? ??? ???? ?????
  
•   
• ????? ??? ?????? ??? ????? ?? ?????
  
  
  
• (infant mortality rate)????? ??? ?????????
  
  x 1000
• ????? ?????? ???? ?? ???? ???
  
  
•  
•  
•  
•  
•  

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• ????? ?????? ???? ?? ?? ?????? ?? ???? ?? ?? ????
  
  
• x100
  ????? ??????
  ??????(case fatality rate)
• ????? ????? ???????? ?? ?? ?????? ?? ??? ????
  ???? ?????
  
• ????? ?????? ???? ?? ?? ?????? ?? ??? ?????
  
  
• x100
  ????? ??? ? ???
  ??????(proportional mortality rate )
  ????? ????? ????? ?? ?? ????? ?? ??? ???? ???
  
  

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An age standardized death rate is a summary
measure of the death rate that a population would
have if it had a standard age structure.
?????? ???? ?????? ? ?????? ???? ????????? ????? ????????? ????? ??? ??????? ??? ?????? ???? ????? ? ????? ??? ??????? ??? ?? ???????? ????? ??? ?? (???)
0.7 0.7 350 0.002 0.002 lt15
4.5 2.7 450 0.01 0.006 44-15
4 4 200 0.02 0.02 45
9.2 7.4 1000 ---- ---- ???? ????
?????? ????? ?????? ???? ?????? ?? ????????
??????? ??? ????? ?? ??? ??????
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• ????? ????? ????? ?? ?? ?????? ?? ???? ????
  
  
• x 10n
  ????? ????(prevalence
  rate)
• ????? ????? ?? ???? ??? ?? ?????? ?? ???? ????
  
  
  
  
  
  
• ????? ????? ????? ?? ?? ?????? ?? ???? ?? ?? ????
  
  
• x 10n
  
  ????? ???? ???? ??(period
  prevalence rate)
• ????? ????? ?? ???? ??? ?? ?????? ?? ??? ?? ????
  ?????
  

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• ????? ????? ???? ?? ?????? ?? ???? ?? ?? ????
  
• x 10n
  
  ????? ???? ( (incidence rate
• ????? ?? ???? ??? ???? ???? ???? ?????
  
  
  
  
• ????? ????? ?????? ?? ?? ???? ?? ?? ???? ?? ????
  ???
  
• x 10n
  
  ????? ???? ( (incidence
  rate
• ?????? ?? ?? ?? ???? ???? ????? ??
  ???? ??? ?????? ???? ???
  

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????? ????(attack rate)

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

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????? ???? ?????? X ???? ????

• ????? ????? ?????? ????? ?? ?? ?? ?? ?? ???? ????
  ?? ?????? ????? ??????
  
• 
  
  x100????? ???? ??????(secondary attack rate)
• ????? ?? ????? ?????? ?????(????? ?? ??????)
  

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Increased by
Decreased by Longer duration of disease
Shorter duration of
disease Prolongation of life of
High case-fatality rate
from patients without cure
disease   Increase in new
cases
Decrease in new cases (increase in incidence)
(decrease in
incidence)   In- migration of cases
In-migration of
healthy people Out- migration of healthy people
Out- migration of
cases   In- migration of susceptible
Improved cure rate of
cases people Improved diagnostic facilities
(better reporting)            
Factors influencing observed prevalence rate
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????? ???? ??????
???? ???????? ????? ??? ???? ???? ?? ?????? ?????? ?????? ?????? ?? ????? ?????? ????? ??? ????? ????? ?????? ?????? ???? ??? ???? (???? ???)
??????????? ??????? ????? ???? ?? ????? ???????? ???????? 100 ???? ?? ?????? ??????? ?? ??? ?????????? ????? ?? ?????? ?? ????? ?? ???? ?????? ????? ??? ?? ????? ?? ?? ???? ??? ?????
???? ?? ?? ????? ????? ???? ?? ????? ???????? ??? ????? ????? 100 ???? ?? ?? ????? ?? ??? ?????????? ????? ?? ?????? ?? ?? ????? ?? ????? ?? ?? ???? ??? ????? ?????
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????? ????(case report)


?????? (descriptive)

????? ?????
(case series)


(observational)?????? ??
(ecologic)
??????
???????? (cross- sectional)
?????(analytic)

(case- control)????-?????

(cohort)

???????
????????? ??????
(clinical trial)
????????? ???????
(experimental) ?????
(community trial)????????? ????
(field trial)
??????? ????????????
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?????? Vassey and Doll ?? ??? 1969

• ???? ???? ????? ?? ?? ????????? ????? ? ????? ??
  ?????? ????? ?? ?????? ???? ???? ??? ???? ?????.
• ???? ???? ????? ?? ?? ???? ????????? ??? ?? ???
  ?????? ????? ????? ?????.
• ?????? ??? ????? ???? ??? ??? ?????? ??? ???? ??
  ???????
• ????? ??? ???? ???? ?? ??????
• ????? ????(matching) ???? ???? ? ???? ?? ??? ???
  ????? ???? ? ????? ??????? ?? ????? ??? ?????.

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Odd Ratio 6
?????? -
24 42
144 42
?????? -
66 186
84 168
21
?????? Framingham ?? ??? 1948

• ????? ??? ?????? ?? 000,28??? ????? ???
  Framingham ? 10,000 ??? ?? ?????? ??? 59-30 ???
  ???? ??????. ?? 6507 ??? ??? ???? ?? ?????? ????
  ??. 5209 ??? ???? ?? ????????. ??????? ????? ????
  ??? ?? 82 ??? ?? ?????? ???? ?????? ??? ?????
  ????? ??? ?? ?????? ???? ???? ? ?? ????? ?? ??
  5127 ??? ????? ????.
• ?????? ??? ??? ????? ??????? ???? ???? ???? ???
  ? ???? ?????
• ????? ??? ???? ???? ?? ????? ???????? ?? ??
  ????? ??????? ?? ?????? ? ??? ??????? ??????

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????? ??? ???? ??? ??????? ???? ????? ? ?? ?????
(1)
??????? ?? ????? ??????? ???? ?????
?? ??? ?? ????? ?? ??? ?? ????? ???? ???? ?? ??? ?? ?? ???? ??? ?? ??? ????? ?????? ?????? ????? ???. ??????? ????? ?????? ?? ?? ????? ?????? ????? ???? ?? ????? ???? ?????? ????? ?? ???. ???? ????? ????? ???? ?? ?????? ????? ??? ??? ?? ??? ?? ??? ????? ????? ?? ????? ?? ????? ?????? ?? ???. 1- ?? ????? ?? ??? ?? ??? 2- ?? ?????? ???? ?? ??? 3-??????? ???? ???? ?????? ??? ????? ?? ?? ????? ????? ???? ?? ????? ???? ?? ?????? ????? ?? ???. 4- ??????? ????? ?????? ???? ????? ?? ????? ??? ??? ???? ????? ??? ??????? ?? ???? ???. 5- ????? ????? ?? ????? ?????? ?? ???.
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????? ??? ???? ??? ??????? ???? ????? ? ?? ?????
(2)
??????? ?? ????? ??????? ???? ?????
??????? ???? ??? ?????? ?????? ???? ? ??? ?? ????? ?? ???. ???? ?????? ??? ????? ???? ???? ????? ????. ????? ????? ??? ???? ? ?????? ??? ???? ?????? (??? ?????) ?? ?????? ?? ??? ?? ????? ????? ?? ?????? ???? ?????? ???????? ?? ???? ???? ?????? ?? ??? ????? ?? ???. ???? ???. 6- ??????? ??? ?? ????? ?? ???. 7- ???? ?????? ??? ?????? ???? ????? ???. 8-??????? ??? ??????? ?? ??? ???? ?? ?? ???? ???? ???? ?? ??? ?? ???. 9- ???????? ?? ???? ?????? ??? ????? ??? ?? ?????? ???? ????? ????? ??? ???. 10- ?????? ????? ???.
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?????? ????? ????? ( ????? ???? ?? ????? ???)
??? ?? ????????? ???? ??? ?????? ???
?????? ??? ????? ( ????? ???? ?????? ?? ????
?????)
????? ?? ???? ????? ??????
???? ???? ?????? ?? ??????? ???? ?? ?????? ????
????
????? ?? ??? ?????? ????? ???? ?? ????? ????
?????? ????
???? ????
???? ???? ?????
??? ???? ? ??????
???????
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??? ????? ??????
??????
?????? ????? ?? ?????? ???
?????? ???????
???????
???? ?????? ?? ?????? ???
????
? ????? ??????
?????? ????? ??? ??????? ?????? ????? ? ????
?????? ???????
??????
?????? ????? ?? ?????? ???
???????
???? ?????? ?? ?????? ???
????
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????? ???????(bias)

• ??????? ?????? (selection bias)
• ??????? ???????(recall bias)
• ??????? ?????? ?????(interviewers bias)
• ??????? ?? ??? ????? ????? ?????(confounding
  bias)

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Blinding

• single blind trial (????????? ?? ???? ???)
  
• double blind trial (????????? ?? ???? ???)
  
• triple blind trial(????????? ?? ???? ???)
  

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????? ?????? ??????? ????? ?????? ??
???????? ????? ???? ????? ???????
?????? ??????? ?????? ??????? ??????? ???? ?? ?????? ????? ??? ???? ??? ??? ????? ?? ?????? ?? ?????? ?? ?????? ???? ????? ????? ????? ???? ?? ?????? ????? ????? ????? ???? ???? ????? ????? ????? ????? ????? ????? ???? ????? ???? ????
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????? ?????? ?????? (??????) ?????? ?????? ??????
????? ?????? ?????? (??????) ????? ????? ?????
????? ?????? ?????? (??????) ????? ????? ???? ????? ??????
?????? ?? ??? ????? ??? ???????? ????? ???????
??????? ??? ??? ??? ???
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• Validity (Accuracy) ???? ?????? ????? ?? ?????
  ?? ??????
• Reliability (Precision) ????? ???? ????? ??
  ????? ?????

(??????????????????????)
(??????? ???? ??????????)
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????? ?????? ??

• ??? ?????? ??? ?? ???? ????? (common source
  epidemics)
• ? ?????? ??? ???????? (propagated epidemics)
• ? ?????? ??? ???? (slow epidemics)

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??? ???? ???? ????? ?????- ??????? 1854
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?????? ???? ?? ??? ??? ?? ????? ????
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????? ????? ?? ??????

• ??? - ????? ????? ??????
• ? ????? ???? ??????
• ? ????? ????? ?? ???? ???
• ? ?????? ???? ???? ???? ???? ??? ???????? ?
  ??????? ??????? ????
• ? ??????? ????? ????????
• ? ????? ????? ????? ?? ???? ???
• ? ????? ? ????? ???? ??
• ? ????? ?????
• ? ????? ?????
• ? ????? ?????

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Home page http//medicine.tums.ac.ir/en
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????? ???? ?? reliability(??????)

• ??? ???????? ?????? ???????
• 1- ???????? ?? ???? ?????? ???????((Intra
  observer variation
• 2- ???????? ?? ??? ?????? ???????((Inter observer
  variation
• ?- ???????? ????????
• 1- ??????? ?? ???????? ?? ?????? ???? ?? ???
• 2- ??????? ?? ???? ??? ????? ?? ????? ???? ? ????
  ???? ??? ?? ?? ??????
• 3- ?????? ?? ???????
• ?-?????? ???? ?? ?????? ???

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????? ?????? ???(total fertility rate) ???????
????? ???????? ?? ?? ?? ?? ???? ?? ???? ?? ???
???? ?? ???????? ?????? ??????? ??? ????? ?????
????? ???.

• ????? ??????? ???? ?? ?????
  
• 
  x1000????? ??? ???? (crude birth rate)
• ????? ??? ???
• ????? ??????? ???? ?? ?? ????? ??
  ?????
  
• 
  x1000 ????? ?????? ????? (general
  fertility rate
  
  )
• ????? ???? 15 ?? 44(?? 49)??? ?? ????
  ????? ?? ??? ???
  

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???? ?? ????? (life expectancy) ?????
??????? ?? ???? ?? ??? ?? ??? ???? ????? ?? ????
?? ??????? ???? ?????? ?????? ????

• ????? ????? ???? ?? 15 ???
  ????? ????? 65? ????? ?? 65 ???
  
  
  
  
  
  
  
  ???? ??????
  (dependency ratio)
• ????? ????? 15 ?????64 ???
  

????? ??? ????? ??? ??? - ????? ??? ????
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• ???? ??? (eradication) ??? ?????? ????? ?? ???
  ???? ???????? ??
  ???? ??????
• ??? elimination)) ????? ?? ?????? ?? ???? ??
  ????? ????? ????? ??
  ?? ?????? ???.

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Basic Biostatistics

• Payman Salamati ,MD,MPH,
• Assistant Professor of community Medicine
• Tehran University of Medical Sciences
• 1387

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