Canadian Census Health and Environment Cohorts (CanCHECs): Creation of a new health surveillance program - Transcript
(The Statistics Canada symbol and Canada wordmark appear on screen with the title: "Canadian Census Health and Environment Cohorts (CanCHECs): Creation of a new health surveillance program")
Hello. Today I would like to talk to you about a new health surveillance program at Statistics Canada: The Canadian Census Health and Environment Cohorts, known as the CanCHECs.
The CanCHECs are population-based datasets that include the non-institutional population at time of census linked to different health outcomes. Currently, these outcomes include mortality, hospitalization and cancer.
Data gaps were the main reason for the creation of the CanCHECs. On the one hand, national administrative health databases contain detailed information about a person's health outcomes but little information about the actual person beyond basic demographic data. On the other hand, the long-form census databases contain detailed socioeconomic and ethnocultural information about individuals in the Canadian population, but have little to no information about their health.
Linking these data sources together to create the CanCHECs allows us to examine the health outcomes of Canadians across many characteristics including income, education, occupation, language, ethnicity, First Nations, Métis, Inuit, and immigration status.
There are currently 5 CanCHECs in use and accessible to users through the Canadian Research Data Centre network. They correspond to the five census years from 1991 to 2011. As you can imagine, the CanCHECs are a rich data source that can be used to measure and examine health inequalities across socioeconomic and ethnocultural dimensions in both time and space. They can also be used to examine the effects of exposure to environmental factors on human health.
The CanCHECs are created by applying a series of inclusion criteria to individuals who are enumerated by the census of population. These criteria include: the person has to be living in Canada and in a non-institutional household on census day. Then, only those records that are linked to the Derived Record Depository without duplication and whose death record occurs after census day are included. When linkage is completed, identifying information is removed from the records to ensure confidentiality and privacy as required by the Statistics Act. In the end, each CanCHEC consists of those who meet the inclusion criteria and are also long-form census respondents. It is important to note that applying the cohort weight produces estimates representative of the non-institutional population living in Canada at the time of census.
Now let's walk through an overview of some of the attributes and data sources that make up the CanCHECs.
The CanCHECs are large. The number of cohort members ranges from 2.6 million in the 1991 CanCHEC to a high of 6.5 million in the 2011 CanCHEC. This helps make any CanCHEC an excellent data source to examine rare health outcomes and small population groups.
The age at baseline ranges from 25 or older in the 1991 CanCHEC to age 0 starting with the 2006 CanCHEC. This is something to keep in mind if you are interested in examining trends over time.
The Canadian Vital Statistics Death Database is an administrative data source that collects information annually from all provincial and territorial vital statistics registries on all deaths in Canada. The database includes information such as age at time of death, date of death and underlying cause of death. For each CanCHEC, mortality data are available annually starting with the census year up to 2016.
The Canadian Cancer Registry is a person-oriented, population-based registry established in 1992. It includes data collected annually by each provincial and territorial cancer registry. The database includes information such as the primary cancer diagnosis, characteristics of the diagnosed cancer, and age at time of cancer diagnosis. Canadian Cancer Registry data are available annually from 1992 to 2015 for each CanCHEC. It is important to note that there are no cancer cases from Quebec in the registry from 2011 onward.
The Discharge Abstract Database – known as the DAD - captures administrative, clinical and demographic information on hospital discharges, including deaths, sign-outs and transfers. Some provinces and territories also use the DAD to capture day surgery. This database includes information such as admission and discharge dates, length of stay, procedures and diagnosis. DAD data are available from 2000 to 2017 for the 2006 and 2011 CanCHECs only. It is important to note that Quebec is excluded from the DAD, and Nunavut data are not available for the period 2002/2003.
The National Ambulatory Care Reporting System – known as NACRS - contains data for all hospital-based and community-based ambulatory care related to day surgery, outpatient and community-based clinics, and emergency departments. The database includes information such as age at admission and emergency room diagnosis. NACRS data are available annually from 2002 to 2018 for the 2006 and 2011 CanCHECs only. It is important to note that NACRS does not include Quebec, and information is not complete for some years in certain provinces and territories.
Annual postal codes from mailing addresses for cohort members aged 15 years or older are available from 1981 to 2016 for all CanCHECs. While the earlier CanCHECs had at least one annual postal code attached to each record, this is not the case for the more recent CanCHECs for two reasons. First, the 2006 and 2011 CanCHECs include cohort members under the age of 15 and secondly, only those who agreed to have their information linked to their tax record on both the 2006 Census and 2011 National Household Survey could have annual postal codes attached to their records.
Note that there may also be certain years in which a postal code may be missing but in general the intention of this file is to allow users to track mobility year over year.
The CanCHECs have several important features that users should keep in mind. As mentioned earlier, they include only the non-institutional population living in Canada on census day. Using the cohort weight that is provided with each CanCHEC ensures that estimates are representative of this population as a whole and not just representative of the individuals included in each CanCHEC. Using the bootstrap weights ensures that the appropriate variance is calculated for all estimates. Users create their own analytical cohort files by putting together the component files they need for their research using the common linking keys that are provided and metadata is available for each of the component files and each CanCHEC year also has a user guide.
The CanCHECs have many strengths. All characteristics and outcomes are linked at the individual level. A consistent linkage methodology is used for all CanCHECs so that trends over time both within and between CanCHECs can be examined.
Annual postal codes allow users to attach ecological or time varying variables to each cohort. As new years of administrative data and new administrative data are added to the Derived Record Depository, the CanCHECs can be updated to prolong follow-up periods and to include new data sources.
The CanCHECs can and have been used in multiple ways. It is possible to examine health outcomes by population groups such as Indigenous peoples and immigrants; to examine health outcomes by socioeconomic status such as income, education and occupation; and examine health outcomes of specific occupations, occupational groups, and job characteristics; as well as to measure the effect of the environment on health such as exposure to air pollution or greenness.
Since 2008 there have been over 65 peer reviewed journal articles based on the CanCHECs. What follows are some examples of recent CanCHEC-based research that has been or soon will be published.
This first example is a study that used four CanCHECs from 1996 to 2011 to examine trends in life expectancy among First Nations, Métis and Inuit over time.
Another study used all five CanCHECs to examine trends over time in education and income-related mortality inequalities among adults.
The 2011 CanCHEC was linked to 5 years of hospitalization data to examine rates of hospitalization due to opioid poisonings. Rates were presented according to characteristics such as visible minority status, education, income and labour force status.
This study used the annual postal code file to attach air pollution exposure data and ecological characteristics such as population centre size to the 2001 CanCHEC, and examined the association with mortality.
And this study also used the annual postal code file to attach ultraviolet radiation exposure data to the 1991 CanCHEC, and examined its association with melanoma.
Some considerations when using the CanCHECs include its population exclusions; mainly that the people living in institutions on census day are excluded from the CanCHECs. As a result, CanCHEC data represent a healthier population than the general population.
The CanCHEC datasets grossly underestimate infant mortality because about three-quarters of all infants who die do so within the first 28 days. This makes enumeration by a census uncertain. As a result, life expectancy at birth cannot be reliably estimated using the CanCHECs.
Census characteristics are only collected at the time of census and may not reflect a person's socioeconomic profile over their lifespan.
No information regarding baseline health (with the exception of activity limitation) or health behaviour risk factors such as smoking are collected. However, some CanCHEC projects have applied population-level and individual-level indirect adjustment techniques using the Canadian Community Health Survey data to try and account for this.
Not all years of the various health administrative databases are available for all provinces and territories, and there may be jurisdictional differences in data quality.
And finally, if analysis across CanCHEC years is of interest, it is important to consider changes over time to the census itself, including its mode of collection, that the 2011 National Household Survey was voluntary rather than mandatory, and that some census variables may not be available in a given year or may have been modified over time.
So how can you access the CanCHECs? The CanCHECs are available to users through the Canadian Research Data Centre Network. The Statistics Canada website provides the information you need including which CanCHECs are currently available in the research data centres, how to apply for access to these data, as well as a list of approved projects within the last 12 months that are using the CanCHECs.
If you would like more information about the CanCHECs, please email Statistics Canada at the address you see on the screen (email@example.com)
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