Updated Reference Population, Age-Standardized Rates

This notice is for people requesting or using Cancer Care Ontario data.

We have updated the reference population for age-standardized rates from the 1991 to the 2011 Canadian population. This approach is in line with Statistics Canada’s recommendations and other major Canadian organizations. This change comes from the need for a more recent reference population with an age structure that better resembles the current population. It primarily affects incidence and mortality rates.

Using a more recent reference population has several implications:

• Rates that are more relevant – Rates standardized to the age distribution of the 2011 standard population are closer to the unadjusted or “real” rate.
• An increase in rates – The increase is simply a result of standardizing to a more recent population and does not reflect a true increase in the event (new cases, mortality) in the population. The amount of increase varies by cancer type.
• Lack of comparability – Rates standardized to the new population will not be comparable with rates age-standardized using another reference population (such as previously published statistics using the 1991 Canadian population).

Data requesters have the option of specifying their preferred reference population (either 1991 or 2011) when requesting data that includes age-standardized rates. See Access Data on the CCO website for more information about requesting Cancer Care Ontario data.

It is important to note that age-standardized rates are artificial and are only appropriate for specific purposes, such as comparisons over time or between populations. Age-standardization can mask age-specific patterns and diminish the true burden of an event in a population.

Email the Cancer Care Ontario Surveillance team for more information.