Indirect Standardization
- Adjusts comparisons of rates or proportions between groups by accounting for differences in confounding-variable distributions (for example, age or smoking prevalence).
- Applies a rate from a standard population to each group’s characteristics to produce an adjusted comparison.
- Commonly used in epidemiological studies to compare incidence or mortality between populations.
Definition
Section titled “Definition”Indirect standardization is a statistical method used to compare rates or proportions between two or more groups while controlling for the effects of confounding variables. It is commonly used in epidemiological studies to compare the incidence or prevalence of a disease or the mortality from a condition between different population groups.
Explanation
Section titled “Explanation”Indirect standardization proceeds by taking a rate measured in a standard population (the standard population rate) and using it to adjust the observed rates in each study group. This adjustment accounts for differences in the distribution of confounding variables across groups, producing a more accurate comparison of the outcome of interest between those groups. The method isolates the effect of the variable of interest on the outcome by controlling for confounders referenced in the study.
Examples
Section titled “Examples”Breast cancer by ethnic group
Section titled “Breast cancer by ethnic group”A study compares breast cancer rates between African American and White women. The researchers:
- Calculate the overall incidence rate of breast cancer in the general population (the standard population rate).
- Calculate the incidence rate of breast cancer within each ethnic group (the observed rate).
- Use the standard population rate to adjust for differences in the distribution of age between the two ethnic groups. This produces a comparison of breast cancer rates between the groups that controls for the effect of age.
Lung cancer mortality by city
Section titled “Lung cancer mortality by city”A study compares lung cancer mortality rates between Los Angeles and New York. The researchers:
- Calculate the overall mortality rate of lung cancer in the general population (the standard population rate).
- Calculate the mortality rate of lung cancer in each city (the observed rate).
- Use the standard population rate to adjust for differences in the distribution of smoking prevalence between the two cities. This yields a comparison of lung cancer mortality between the cities that controls for the effect of smoking.
Related terms
Section titled “Related terms”- Confounding variable(s)
- Standard population rate
- Observed rate
- Epidemiological studies