PAPP101 - S06: Mortality statistics and standardisation

Indirect standardisation (cont.)

In direct standardisation, we take the observed age-specific mortality rates from a study population and apply them to a standard population in order to calculate an age-adjusted summary rate.

Another approach to comparing mortality in populations can be used if we know:

the age-specific mortality rates for a standard population
the age structure of the study populations
the total number of deaths in the study populations

Using these, we can calculate the number of deaths that would be expected if both populations had the same (standard) age-specific death rates, but kept their real age structure. This is called indirect standardisation .

To use indirect standardisation on (for example) death rates, we apply a set of standard age-specific death rates to the real age structure of the study population, and compare the total number of expected (calculated) deaths with the number actually observed.

The standard population could be one of the populations under study, or another population.

A technique by which the specific rates in the standard population are averaged, using as weights the distribution of the study population. The ratio of the crude rate for the study population to the weighted average is the standardised mortality (or morbidity) ratio (SMR).