Page 346 - Contributed Paper Session (CPS) - Volume 2

CPS1879 Zineb El O.T.
2. Methodology
In epidemiology and demography, age adjustment, also called age
standardization, is a technique used to allow populations to be compared
when the age profiles of the populations are quite different. The direct method
of standardization involves the application of age-specific rates in a
population of interest to a standard age distribution in order to eliminate
differences in observed rates that result from differences in population
composition. The resulting age standardized rate may be named Age Adjusted
Rate.
An age-adjusted rate adjusted by the direct method produces a rate that
would occur if the observed age-specific rates in the study population were
present in a population with an age distribution equal to that of the standard
population. Similarly, the age adjusted rate is the rate that would occur if the
observed age specific rates in the study population were present in a
population with the age distribution of the standard.
The requirements for this calculation are:

• Number of events for each age group in the study population
• Population estimates for each age group in the study population
• Population for each age group in the standard population

Formulae
is the observed number of events in age group i in the study population

is the number of persons in age group i in the study population

is the event rate in study population for the persons in age group i

is the number of persons in age group i in the standard population

is the expected number of events in age group i in the standard

population
For each age category, the age-specific (crude) rate is calculated by dividing
the number of events by the study population for that age category.

Age-specific crude rate = = /

For each age category, the age-specific crude rate is multiplied by the age-
specific standard population to obtain the expected number of events.

Age-specific expected events = E = r * P
i
i
i
The Standardized Rate is the sum of all expected events divided by the
total standard population

∑
∑

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