Canadian Oral Health Survey (COHS)

Detailed information for November 2023 to March 2024 (Cycle 1)

This survey gathers information on Canadians' oral health, including their ability to pay, challenges and experiences with the oral health care services, and care needs. Additionally, the survey collects information on knowledge of publicly funded oral health programs and access to dental care expenses and insurance coverage to better understand the state of oral health.

Data release - August 27, 2024 (Provisional); October 23, 2024

• Questionnaire(s) and reporting guide(s)
• Description
• Data sources and methodology
• Data accuracy

Description

Statistics Canada and Health Canada have partnered to conduct the Canadian Oral Health Survey (COHS) with the shared goal of understanding the oral health of Canadians. The COHS is gathering information related to oral health, including individuals' ability to pay for oral health care, experiences with the oral health care system, challenges finding oral health services, and care needs.

The following are some of the topics the COHS includes:

- Awareness and intentions of the newly formed Canadian Dental Care Plan
- Oral health status
- Presence of natural teeth and/or dental prosthesis
- On-going and/or untreated mouth problems or pain
- Oral health behaviours (e.g., brushing of teeth, flossing)
- Visits to an oral health professional
- Oral health care
- Dental care and related costs
- Dental care treatment and/or avoidance
- Risk factors and related conditions
- Health of your mouth and general health status
- Oral health insurance (e.g., public or private insurance coverage of dental care expenses)

All of this valuable information will create national baseline data on various aspects of oral health care. In addition, information from this survey will be used to inform policies and monitor changes in the oral health of Canadians over time.

Reference period: 2022-2024

Collection period: November through March

Subjects

• Children and youth
• Health
• Lifestyle and social conditions

Data sources and methodology

Target population

The target population for COHS consists of Canadian households with adults 18 years of age and older, living in the 10 provinces.

The observed population excludes: persons living on reserves and other Indigenous settlements in the provinces; persons living in the three territories; the institutionalized population and members of the Canadian Forces living on a base.

Instrument design

The content of this survey was developed in partnership with Health Canada.

Prior to finalizing the questionnaire, one-on-one qualitative test interviews were conducted in both official languages. The objective of these interviews was to test the questionnaire's content, in particular the wording of instructions, questions and help text, and the flow of questions. As a result of this testing, improvements were made to the questionnaire. Qualitative testing was done with guidance and input from Statistics Canada's Questionnaire Design Resource Centre (QDRC).

Sampling

This is a sample survey with a stratified two-stage sample and cross-sectional design.

At the first stage, the sample is selected from a stratified list frame of dwellings; at the second stage the sampling unit is adult. The selected adult will provide information for themselves, their households, and all persons under the age of 18 in the household (children). As some information will be provided for the entire household and all the children in the household, the design for those units could be considered as one-stage.

Sampling unit
The COHS uses a stratified two-stage design. The sampling unit for the first stage is the dwelling, and the sampling unit for the second stage is the adult.

Stratification method
The dwelling frame was stratified by province, household income, and household composition (presence or absence of seniors). A simple random sample of sampling units was selected independently within each stratum.

Sampling and sub-sampling
The COHS sample has a two-stage design. First, dwellings will be randomly selected across Canada. Next, within each selected household, one individual aged 18 and over will be selected based on specific instructions within the letter they receive (or provided by the interviewer if they respond by phone). The instructions will use the age of household members to determine who is selected and will vary from one household to another. For some households, the oldest member is selected, others the second oldest, or the youngest, etc. These letters are randomly assigned to the selected dwellings ensuring that the selected individual from within the dwelling is random.

The primary sample of 45,000 dwellings is allocated provincially to yield comparable number of respondents in each province. Within each province, extra sample is allocated to strata more likely to contain persons eligible to enroll in Canadian Dental Care Plan.

The supplementary sample of 10,000 dwellings is allocated evenly to ten provinces to the strata where we expect to reach seniors likely to enroll in the Canadian Dental Care Plan.

The total sample size sent to data collection is 55,000.

Data sources

Data collection for this reference period: 2023-11-27 to 2024-03-13

Responding to this survey is voluntary.

Data are collected directly from survey respondents.

Data are collected using an electronic questionnaire and computer assisted telephone interview software (CATI).

The first contact with respondents is a letter sent through the mail. On the letter there is a code which gave access to the online questionnaire. Statistics Canada will contact invited participants by email or mail to follow up if the respondent's completed questionnaire is not received. The electronic questionnaire takes on average 25 minutes to complete.

Proxy reporting is not allowed on COHS. Respondents are offered to complete the interview in either English or French.

Administrative data sources
The information collected during COHS was linked to the Administrative Personal Income Masterfile (APIM, a comprehensive, centrally processed source of personal income data generated from tax returns and associated tax slips from the Canada Revenue Agency, CRA), the Longitudinal Immigration Database (IMDB, administrative immigration data for all immigrants since 1952 and non-permanent residents since 1980), and the 2021 Census. Household information (address, postal code, and telephone number), respondent's information (surname, name, date of birth/age, sex) and information on other members of the household (surname, name, age and sex) are key variables for the linkages.

Respondents are notified of the planned linkage before and during the survey. Any respondents who object to the linkage of their data have their objections recorded, and no linkage to their tax data takes place.

View the Questionnaire(s) and reporting guide(s) .

Error detection

Editing occurred at several points throughout the survey process and ranged from simple preliminary checks performed by the electronic questionnaire application to more complex automated verifications performed at the processing stage after the data have been collected. In general, edit rules are determined by what is logically or validly possible, based upon expert knowledge of the subject matter, other related surveys or data, structure of the questionnaire and its questions, and statistical theory.

There are three main categories of edits: validity, consistency and distribution edits. Validity edits verify the syntax of responses and include such things as checking that the data lie within an allowed range of values.
Consistency edits verify that relationships between questions are respected. For example, it ensured that questions that did not apply to the respondent were not asked.

Distribution edits are performed by looking at data across questionnaires. These edits attempt to identify records that are outliers with respect to the distribution of the data. Distribution edits are sometimes referred to as statistical edits or outlier detection.

The data underwent a series of processing steps that resulted in some of the data being adjusted. As a final validation step, the edits were applied to the processed data. As a result, the final data were complete and contained reserve codes for response of "valid skip", "don't know", "not stated".

Imputation

The total personal income and the adjusted family net income in the COHS were imputed using donor imputation when the respondents could not be linked to APIM.

The respondent's geography information was based on their household's postal code. In situations where the postal code on the sample file was missing, the respondent-provided postal code (if any) was used along with online search and information from records in the same geographical area (from the frame) to impute the postal code.

Estimation

In order for estimates produced from survey data to be representative of the covered population, and not just representative of the sample itself, users must incorporate the survey weights in their calculations. A survey weight is given to each respondent included in the final sample. This weight corresponds to the number of respondents (persons or households) in the entire population that are represented by the respondent.

As described above, the COHS was a single frame survey with a two-stage design. At the first stage, the sampling unit was the dwelling; at the second stage, the sampling unit was the adult. The selected adult provided information for themselves, their households, and all persons under the age of 18 in the household (children).

Two sets of weights were produced for the COHS: a set of household-level weights, and a set of person-level weights (adult weights and child weights). The weighting process started with weighting of the primary sampling unit (dwelling), which resulted in the household weight. The household weight yielded the person-level weight for the child population (all children in the same household have the same weight), as all the children in the same household had the same probability of selection and they were all selected. The household weight was then used to derive the person-level weight for the adult population. The final weighting steps of winsorization and calibration were then applied.

Bootstrap weights are created through resampling the original sample by applying similar adjustments to the bootstrap weights as to the sample weights. Bootstrap weights are used to evaluate the quality of survey estimates.
The steps for weighting are described in chapter 9 of the COHS User Guide.

The sample design used for this survey is not self-weighting. That is to say, the sampling weights are not identical for all individuals in the sample. When producing simple estimates, including the production of ordinary statistical tables, users must apply the proper sampling weight. For person indicators, the person weight should be used, while household weight should be used for household indicators. If proper weights are not used, the estimates derived from the data file cannot be considered to be representative of the survey population and will not correspond to those produced by Statistics Canada.

Estimates of the number of records with a certain characteristic are obtained from the data file by summing the final appropriate weights of all records possessing the characteristic of interest.
Proportions and ratios are obtained by summing the final weights of records having the characteristic of the numerator and the denominator, and then dividing the first estimate by the second.

Quality evaluation

Throughout and after COHS data collection, data were compiled and reviewed in terms of the accuracy, coherence and overall reasonableness. Any inconsistencies were reviewed and the appropriate solution was implemented.

Open-ended questions were recoded by subject matter during post-collection processing. Sociodemgraphic open-ended questions were recoded based on standardized recoding rules. Non-sociodemographic open-ended questions were recoded based on recoding guidelines developed from a qualitative review of the types of text responses given.

Disclosure control

Statistics Canada is prohibited by law from releasing any information it collects which could identify any person, business, or organization, unless consent has been given by the respondent or as permitted by the Statistics Act. Various confidentiality rules are applied to all data that are released or published to prevent the publication or disclosure of any information deemed confidential. If necessary, data are suppressed to prevent direct or residual disclosure of identifiable data.

The standard table symbol X was used to indicate the data were suppressed to meet the confidentiality requirements of the Statistics Act.

It is Statistics Canada practice to remove personal identifiers from statistical master files when they are no longer required for data processing or other authorized purposes.

Revisions and seasonal adjustment

This methodology type does not apply to this survey.

Data accuracy

The survey aims at producing unbiased national and provincial estimates of good quality. Age group and sex breakdowns are also possible, but careful considerations of sample size and quality indicator (confidence interval) must be taken into account.

Response rates
In total, 51,793 of the selected dwellings in the COHS were in-scope for the survey, out of which a response was obtained for 27,039 dwellings, resulting in a response rate of 52.2%.

Non-sampling error
Considerable time and effort were spent to reduce non-sampling errors in the COHS. Quality assurance measures were implemented at each step of data collection and processing to monitor the quality of the data. These measures included the use of highly skilled interviewers and extensive training with respect to the survey procedures. Testing of the collection application was also an essential procedure to ensure that data collection errors were minimized.

Non-response bias
A major source of non-sampling errors in surveys is the effect of non-response on the survey results. The extent of nonresponse varies from partial nonresponse (failure to answer just one or some questions) to total nonresponse. Cases of partial response were kept on the final data set, as long as the minimum response criteria were met. Total nonresponse occurred either because a person refused to participate in the survey or because the interviewer was unable to contact the selected person. Total nonresponse was handled by adjusting the weight of persons who responded to the survey to compensate for those who did not respond.

Coverage error
The target population for the survey consists of Canadian households with adults 18 years of age and older living in the 10 provinces.

The observed population excluded: persons living on reserves and other Indigenous settlements in the provinces; persons living in the three territories; the institutionalized population and members of the Canadian Forces living on a base.