Standardization is a process used to make rates such as mortality rates comparable between populations with different age distributions. There are two main methods: direct standardization which applies the age-specific rates of the populations to a standard population, and indirect standardization which calculates a standardized mortality ratio by taking the ratio of observed to expected deaths based on a standard population's rates. Standardization allows unbiased comparison of health outcomes between groups after removing the effect of differences in age composition.

1. PRESENTED BY: DR.
KUNAL
GUIDED BY: DR.
ABHAY MUDEY
STANDERDIZATION

2. What is standardization?
 The development and application of a
standard for a particular measures or
type of component or range of
measurements or proportions or rates.
 The process by which you derive a
summary figure to compare health
outcomes of groups.
 The process can be used for mortality
or morbidity data.
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 What distinguishes standardization of
rates from other stratified methods of
controlling for confounding, is use of
an external standard as the basis for
comparison.

4. Basic Measurement
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o Ratio
o Proportion
o Rates-
o Case fatality rate
o Mortality rates(age specific/cause specific)

5. Crude vs. standerdized
PREFER
REJECT
Uniform Localized
Adapted
Line shows
likelihood
of
correction

6. Standardization Of Rates
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 Used to reduce distortion in
comparisons between crude areas
 Also referred to as adjusting rates

7. Crude rate
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 Advantages
 Actual Summary rates
 Easy calculation for international comparisons
 Disadvantages
 Since population vary in composition (e.g.,
age)
differences in crude rates difficult to interpret

8. Specific Rate
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 Advantages
 Homogenous subgroups
 Detailed rates useful for public health and
 Epidemiological aims
 Disadvantages
 Cumbersome to compare subgroups of two or
 more populations

9. Adjusted Rates
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 Advantages
 Summary statement
 Differences in group composition “removed”
 allows unbiased comparison
 Disadvantages
 Fictional rates
 Absolute magnitude dependent on standard
 population chosen
 Opposing trends in subgroup masked

10. Direct Adjusted Rates
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 Requires a standard population, to which the
estimated age-specific rates can be applied
 Choice of the standard population may affect
the magnitude of the age-adjusted rates, but
not the ranking of the population

11. Direct Adjusted rates
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 Multiply standard population by age-
specific rates for populations A and B
to determine the standardized rates
 Compare standardized rates

12. Population, deaths, death rate by
community & by age
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Community A Community B
Age
(year)
Population Deaths Death Rate
(per 1000)
Population Deaths Death Rate
(per 1000)
Under 1 1,000 15 15.0 5,000 100 20.0
1 – 14 3,000 3 1.0 20,000 35 1.0
15 – 34 6,000 6 1.0 35,000 35 1.0
35 – 54 13,000 52 4.0 17,000 85 5.0
55 – 64 7,000 105 15.0 8,000 160 20.0
Over 64 20,000 1,600 80.0 15,000 1,350 90.0
All ages 50,000 1,781 35.6 100,000 1,740 17.4

13. Standard Population by Age and Age-
Specific Death Rates
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Age
(years)
Standard
populatio
n
Death
rate
in A
(per
1,000)
Expected
deaths
at
A’s rate
Death
rate
in B
(per
1,000)
Expected
deaths at
B’s rate
Under 1 6,000 15.0 90 20.0 120.0
1 – 14 23,000 1.0 23 0.5 11.5
15 – 34 41,000 1.0 41 1.0 41.0
35 – 54 30,000 4.0 120 5.0 150.0
55 – 64 15,000 15.0 225 20.0 300.0
Over 64 35,000 80.0 2,800 90.0 3,150
Total 150,000 35,6 3,299 17.4 3,772.5
Age –
adjusted
death
rate (per
1000)
22.0 25.0

14. Indirect Adjustment of Rates
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 Used if age-specific rates cannot be
estimated
 Mirror image of the direct method

15. Indirect Adjestment Of Rates
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 Based on applying the age-specific
rates of the standard population to
the population of interest to
determine the number of “expected”
deaths.
Standardized Mortality ratio

16. Standardized Mortality Ratio
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Total observed deaths
in a population
-----------------------
Total expected deaths
in a population

17. Standardization Examples
o Direct Method requires
 Age-specific rates in the sample
population
The age of each case
The population-at-risk for each age
group in the sample
 Age structure (percentage of cases in
each age group) of a standard population
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18. Indirect Standardization
 Instead of a standard population
structure, you utilize a standard rate
to adjust your sample
 Indirect standardization does not
require that you know the stratum-
specific rates of your cases
 The summary measure is the SMR or
standardized mortality/morbidity ratio
SMR = Observed X 100
Expected
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19. Standardize Mortality Rate
 Expect a Healthy worker effect
 Occupational studies should have SMRs <
100
 Workers tend to be healthier than the
general population which comprises both
healthy and unhealthy individuals
 You cannot compare SMRs
between studies -- only to
the standard population
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20. Standardization:
Age Adjustment (cont.)
 Indirect method requires
 Age structure of the sample population
at risk
 Total cases in the sample population
(not ages of cases)
 Age-specific rates for a standard
population
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21. Age Standerdization
 Occurrence of disease in one area may
appear to be higher than in another
because:
 population structures are different
 one area is older than another
 Standardisation used to adjust for the
effects of age on mortality rates or
other rates
 Direct or Indirect
 Involves the calculation of numbers of
expected events which are then compared
with numbers of observed events.
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22. Example of London and Camden
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23. The problem…
 The crude rates are not comparable
because the age structure of the
populations are different
 What would the expected number of deaths
be in London and Camden if the age
structures were the identical?
This is DIRECT STANDARDISATION called
DIRECT STANDARDISED RATES
 What would the expected number of deaths
be in London and Camden if the age
specific rates were identical?
This is INDIRECT STANDARDISATION called
STANDARDISED MORTALITY RATIO
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24. Direct standardisation – method
1. Decide which standard population to use –
EUROPEAN STANDARD POPULATION
2. Calculate expected deaths if both London
and Camden had the same population
structure as the European standard.
3. Express as a rate per 1,000 or 100,000
population
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25. Direct standardisation
Example of London and Camden
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26. Interpretation of SMRs
 SMR < 100 : lower rate than expected
 SMR = 100 : Expected/standard rate
 SMR > 100 : higher rate than expected
 An SMR of 180 represents a mortality
rate that is 80% higher than expected.
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27. Standardised mortality ratio 2005-07
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28. Which Method To Use?
 If want to compare several population groups
or several time periods use DIRECT as with
INDIRECT can only compare each population
group to the standard.
 INDIRECT is useful to determine if disease
incidence is high or low in one area only.
 If age specific rates for the population
groups are not available or unreliable use
INDIRECT.
 If it is a rare event and therefore number
of deaths in population groups is small
(e.g. ward level CHD deaths) use INDIRECT.
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29. Issues in the use of standardization
 Standardized rates are used for the
comparison of two or more populations;
they represent a weighted average of
the age specific rates taken from a
'standard population' and are not
actual rates.
 The direct method of standardization
requires that the age-specific rates
for all populations being studied are
available and that a standard
population is defined.
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30. Continued....
 The indirect method of standardization
requires the total number of cases
 The ratio of two directly standardized
rates is called the Comparative
Incidence Ratio or Comparative
Mortality Ratio.
 The ratio of two indirectly
standardized rates is called the
Standardized Incidence Ratio or the
Standardized Mortality Ratio.
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31. Continued....
 Indirect standardization is more
appropriate for use in studies with
small numbers or when the rates are
unstable.
 As the choice of a standard population
will affect the comparison between
populations, it should always be
stated clearly which standard
population has been applied.
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32. Continued....
 Standardization may be used to adjust
for the effects of a variety of
confounding factors including age,
sex, race or socio-economic status.
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33. Pros Cons
 Able to compare
different areas
with each other.
 Can look at
trends through
time.
 (Only if ALL use
the same standard
population)
 Need local data
for all age bands
 Rare diseases may
have no events in
specific age bands
so age specific
rates may be
unavailable
 May need to merge
events from
different years or
combine age bands
Pros and Cons of DSRs
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34. Pros Cons
 Can use where
diseases are rare
 Don’t need local
event information
for all age
groups
 Just need total
number of
observed and
expected counts
 Cannot compare
SMRs with each
other unless
population
structures are
identical
 Cannot look at
trends through
time
Pros and cons of SMRs
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35. Summery
 Standardisation can be use in many areas
 Although we’ve looked at mortality, the
technique can be applied in other ways:
 Hospital admissions
 Prevalence/incidence of disease
 Prescriptions
 Etc
● One type of rate is not necessarily more
important than another. Which you choose
depends on the information sought.
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36. Continued....
 Standardized rates provide a kind of
“snapshot” of the overall risk of
disease or death, which can be
compared across
populations.
 Standardization of rates can be
difficult to understand and is
explained in several different ways
depending on the literature source.
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37. Aknowledgement
 Dr. Minakshi Khapre
 Dr. Abhishek Ingole
 Dr. Pramita Mutonde
 All the PG’S in the department.
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38. References
 1. Heinekens CH, Burring JE. Epidemiology in
Medicine. Lippincott Williams & Wilkins, 1987.
2. Farmer, R. Lawperson, R. 2004. Lecture
notes in Epidemiology and Public Health
Medicine pp 67-68. Blackwell Publishing.
 Text Book of Community Medicine
(Fourth Edition)- By. Dr. Kulkarni, Dr. P.P.
Doke, Dr. J.P Baride, Dr. P.Y. Mulay
 Basic Concept & Methodology for the Health
Sciences (Ninth Edition)- By- Wayan W. Daniel
 Community Medicine with recent Advances-
By- A.H. Suryakantha
 Park’s Text Book of Preventive Social Medicine
(23rd Edition)- By_ Dr. K.Park
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