Age-standardized rates may be used to compare different geographic areas or time frames to adjust for any differences in the age structure of the populations that could cause a difference in rates.
It reflects the number of events (e.g., deaths, hospitalizations) that would occur for a given population if that population had the same age distribution as the 1991 Canadian population.
Age-standardized rates have been used to make more valid comparisons than comparing crude rates. Standardization requires adjusting for the effects of varying age structures of different populations and over different periods of time. The importance of age-standardization can be illustrated by using Population X, which has a higher proportion of elderly persons than Population Y. The unadjusted or “crude” mortality rate for Population X would be significantly higher than Population Y solely because it has a higher proportion of elderly persons and the elderly have a much higher death rate than younger people. This concept also applies when comparing one population over different time periods if the age structure of the population changes over time. By standardizing the mortality rates for Population X, we can see what the mortality rate would be like if they had the same age structure as Population Y. The two different populations are now compared directly.