Canadian Health Measures Survey (CHMS)

Detailed information for January 2016 to December 2017 (Cycle 5)

Status:

Active

Frequency:

Every 2 years

Record number:

5071

The Canadian Health Measures Survey (CHMS) aims to collect important health information through a household interview and direct physical measures at a mobile examination centre (MEC), sometimes referred to as a mobile clinic.

Data release - October 18, 2017

Description

The Canadian Health Measures Survey (CHMS), launched in 2007, is collecting key information relevant to the health of Canadians by means of direct physical measurements such as blood pressure, height, weight and physical fitness. In addition, the survey is collecting blood, urine, saliva and hair samples to test for chronic and infectious diseases, nutrition and environment markers and is storing blood, urine and DNA samples at the CHMS biobank for future health research projects.

Through household interviews, the CHMS is gathering information related to nutrition, smoking habits, alcohol use, medical history, current health status, sexual behaviour, lifestyle and physical activity, the environment and housing characteristics, as well as demographic and socioeconomic variables.

All of this valuable information will create national baseline data on the extent of such major health concerns as obesity, hypertension, cardiovascular disease, exposure to infectious diseases, and exposure to environmental contaminants. In addition, the survey will provide clues about illness and the extent to which many diseases may be undiagnosed among Canadians. The CHMS will enable us to determine relationships between disease risk factors and health status, and to explore emerging public health issues.

CHMS data are representative of the population whether they are healthy or not and provide a better picture of the actual health of Canadians.

The following are some of the measures that the CHMS includes:

Physical measures

- Anthropometry (standing height, weight, waist circumference, neck circumference)
- Cardiovascular health and fitness (resting heart rate and blood pressure, modified Canadian Aerobic Fitness Test)
- Musculoskeletal health and fitness (peripheral quantitative computed tomography, mechanography, hand grip strength, sit and reach)
- Physical activity (accelerometry)
- Vision (visual acuity, visual field, retinal photography, intraocular pressure)

Blood measures

- Nutritional status (e.g., Vitamin B12, Vitamin D, ferritin)
- Diabetes (e.g., glucose, glycated hemoglobin A1c)
- Cardiovascular health (e.g., apolipoprotein A1 and B, lipid profile)
- Musculoskeletal health (e.g., procollagen type I N-terminal propeptide, C-telopeptide of collagen type I)
- Environmental exposure (e.g., acrylamides, perfluoroalkyl substances, volatile organic compounds, metals and trace elements)
- Infection marker (toxoplasmosis)

Urine measures

- Environmental exposure (e.g., phthalate metabolites, alternate plasticizers, tobacco, metals and trace elements)
- Nutritional status (e.g., iodine, sodium, potassium)
- Infection marker (chlamydia trachomatis)

Saliva measures

- DNA extraction for future health research projects

Hair measures

- 25 metals and trace elements (e.g., lead, cadmium, mercury)

The CHMS team works closely with the Health Canada and Public Health Agency of Canada Research Ethics Board and the Office of the Privacy Commissioner of Canada in order to address privacy issues and to implement proper laboratory procedures.

Reference period: Varies according to the question (for example: "over the last 12 months," "over the last 6 months," "during the last week")

Collection period: January - December

Subjects

  • Diseases and health conditions
  • Environmental factors
  • Health
  • Lifestyle and social conditions

Data sources and methodology

Target population

The target population for CHMS consists of persons 3 to 79 years of age living in the ten provinces.

The observed population excludes: persons living in the three territories; persons living on reserves and other Aboriginal settlements in the provinces; full-time members of the Canadian Forces; the institutionalized population and residents of certain remote regions. Altogether these exclusions represent approximately 4% of the target population.

Instrument design

The CHMS household questionnaire was conceived in collaboration with specialists from Statistics Canada, Health Canada, the Public Health Agency of Canada and specialists in medical and academic fields. The CHMS questions were designed for computer-assisted personal interviewing (CAPI), meaning that, as the questions were developed, the associated logical flow into and out of the questions was programmed. This included specifying the type of answer required, the minimum and maximum values, on-line edits associated with the question and what to do in case of item non-response.

Each question had to relate to a physical measure. Experts thoroughly reviewed the questionnaire many times during development. They provided valuable feedback on the questions and on the related physical measures.

The CHMS questionnaire and collection application were qualitatively tested to ensure respondent understanding of the questions and to identify any errors.

Sampling

This is a sample survey with a cross-sectional design.

The Canadian Health Measures Survey uses a stratified three-stage sample made up of one or two selected respondents from each dwelling selected in a sampled collection site.

SAMPLING UNIT
The sampling unit at the first stage is a collection site. A collection site is a geographical unit limited to a radius of about 50 km in urban areas and up to 75 km for rural areas. The sampling unit at the second stage is the dwelling and at the third stage, the sampling unit is the person.

STRATIFICATION METHOD
Strata are defined at every stage. At the first stage, collection sites are stratified in the 5 Canadian regions (Atlantic, Quebec, Ontario, Prairies, and British Columbia).
At the second stage, dwellings are stratified in 7 hierarchical groups defined according to the presence or not of age groups and derived using the household composition obtained from recent auxiliary information:

1) dwellings with 3 to 5 year-olds, else
2) dwellings with 6 to 11 year-olds, else
3) dwellings with 12 to 19 year-olds, else
4) dwellings with 60 to 79 year-olds, else
5) dwellings with 20 to 39 year-olds, else
6) dwellings with 40 to 59 year-olds, else
7) other dwellings without household composition or with all ages outside the ones above.

Finally, at the third stage, the persons in the household at the time of interview are stratified in two age groups prior to selection: 3 to 11 year-olds and 12 to 79 year-olds.

SAMPLING AND SUB-SAMPLING

The Canadian Health Measures Survey consists of a full sample and several subsamples.

For the full sample, at the first stage, a sample of 16 collection sites was required. The sites are allocated by region: Atlantic (2), Quebec (4), Ontario (6), Prairies (2) and British Columbia (2). Within each region, sites are sorted according to the size of their population and whether or not they belonged to a census metropolitan area. Within the Prairies and Atlantic regions, they were first sorted by province. Sites are then randomly selected using a systematic sampling method with probability proportional to the size of each site's population.

The sample size determination and allocation for the second and third stage are done together. The target sample size for cycle 5 is 5,700 respondents for the clinic component of the survey, which works out to approximately 356 respondents per collection site. To determine the number of dwellings to sample in each collection site to reach this target, previous response rates were used from both the CHMS and the Canadian Community Health Survey (CCHS). The CHMS and CCHS are both used to calculate:

¿ The expected probability that a dwelling would be eligible for the CHMS (the eligibility rate)
¿ The expected probability that a roster of all occupants of the household would be completed (the roster rate)
¿ The expected probability that a selected person would respond to the household questionnaire (the questionnaire rate)

Finally, rates from the previous CHMS sites are used to calculate the expected probability that a household questionnaire respondent would also be a respondent to the clinic (the clinic rate). Since outside CMA, inside CMA urban and inside CMA urban core (downtown) collection sites each have distinct response rates, each collection site is classified into one of these three categories and the previously mentioned response rates are calculated and applied separately for each category. The distinction between urban and urban core collection sites within the CMAs is based on the dissemination blocks from the census, which are the lowest level of geography used by the census. If a collection site within a CMA has at least 80% of its dissemination blocks designated as core, it is designated as an urban core collection site. If the rate was less than 80%, it is designated as an urban collection site.

Once all of the previous response rates are calculated, a simulation of 100 independent samples of dwellings is performed for the site being sampled. The goal of each of the 100 simulated samples is to use the expected response rates to predict if each sampled dwelling results in 0, 1 or 2 people responding to the clinic. The final frame for the site is used for each simulation. The average expected number of clinic respondents for each age and sex group over the 100 independent samples is used to determine if the specified sample size and allocation are sufficient. The entire simulation of 100 independent samples is performed multiple times with varying sample sizes and allocations in order to settle on a final overall sample size and allocation strategy. The first iteration uses approximate age/sex targets to come up with starting values for the overall sample size and the stratum allocation. Subsequent iterations require manually adjusting the overall sample size and stratum allocation, based on the previous iteration, to produce final values that satisfy the clinic target counts.

The sample is allocated amongst the 6 age group strata (3-5, 6-11, 12-19, 20-39, 40-59 and 60-79), with a small portion of the sample going to an "other" stratum. A maximum number of 35 dwellings per site is selected in this stratum, with fewer being selected for sites that had fewer dwellings in the stratum. This stratum size helped to prevent extreme dwelling sampling weights.

The allocation of the dwelling sample to each of the age group strata is done to allow for the best chance of meeting the age and sex clinic respondent targets for cycle 5 without going too far over. Where possible, the sample is allocated in a way that emphasized the strata where more sample was required to meet the targets.

Once the sample of dwellings is in the field, when the household interviewer makes contact with a sampled dwelling, the goal is to create a roster for the household. A roster is a list of all persons residing in the household and includes pertinent information such as age, sex and whether the individual works full-time for the Canadian Forces. With this information, the computer application randomly selects one or two persons to take part in the remaining part of the survey, including the questionnaire and the clinic visit. The number of persons selected depends on the composition of the household:

¿ If there is at least one child between the ages of 3 and 11, two people are selected: one child between the ages of 3 and 11 and one other person between the ages of 12 and 79.
¿ If there are no children between the ages of 3 and 11, only one person in the 12 to 79 age group is selected.
¿ If there are no one eligible for the survey, no one is selected. This includes households where all in-scope persons are under the age of 3, over the age of 79 and / or are full-time members of the Canadian Forces.

When the roster is completed, the computer application assigns a sampling factor to each eligible member of the household and this information is used to determine the probability of selection. The sampling factor assigned to each individual is based on their age group and sex and the factors vary between groups in order to do a better job of reaching the clinic targets for each age group by sex. In households where two people are selected, the selection of the child (aged 3-11) is done independently of the person aged 12 to 79.

Households with a large number of members can have very large survey weights and therefore be overly influential when calculating survey estimates. To prevent this, two reset values are put in place that would reset some of the sampling factors to 1 when certain conditions were met. In both cases described below, each member of the 12 to 79 age group have an equal chance of being selected:

1. If a household contained six or more people in the 12 to 79 age group, all sampling factors for the 12 to 79 members are reset to 1.

2. If a household contained three or more people in the 12 to 19 age group, all sampling factors for the 12 to 79 members are reset to 1.

Among the full sample respondents, several subsamples will be selected.

For the Fasted subsample, each sampled dwelling is randomly flagged to indicate whether a respondent should fast prior to the MEC appointment. It requires that respondents fast for at least 10 hours, whereas shorter eating restrictions were imposed on those with non-fasted appointments. Pregnant women, people with diabetes, youth less than 6 years old and other special cases were not asked to fast, even if the dwelling was flagged to be fasted. This random allocation reduces the potential for bias, which could occur if respondents were given the option to fast. The target fasted subsample size is 2,500 respondents aged 6 to 79.

For the acrylamide subsample, respondents 3 to 79 year old attending the MEC are randomly selected to be included or excluded from this subsample. The targeted subsample size is 2,500 respondents: 500 respondents 3 to 5 year old, 500 respondents 6 to 19 year old by sex and 500 respondents 20 to 79 year old by sex.

For the methyl and inorganic mercury subsample, respondents 3 to 19 year old attending the MEC are randomly selected to be included or excluded from this subsample. The targeted subsample size is 1,500 respondents: 500 respondents 3 to 5 year old and 500 respondents 6 to 19 year old by sex,
For the chromium and perfluoroalkyl substances subsample, respondents 3 to 79 year old attending the MEC are randomly selected to be included or excluded from this subsample. The targeted subsample size is 2,500 respondents: 500 respondents 3 to 5 year old, 500 respondents 6 to 19 year old by sex and 500 respondents 20 to 79 year old by sex.

For the environmental contaminants in urine subsample, respondents 3 to 79 year old attending the MEC are randomly selected to be included or excluded from this subsample. The targeted subsample size is 2,500 respondents: 500 respondents 3 to 5 year old, 500 respondents 6 to 19 year old by sex and 500 respondents 20 to 79 year old by sex.

For the volatile organic compounds subsample, respondents 12 to 79 year old attending the MEC are randomly selected to be included or excluded from this subsample. The targeted subsample size is 2,500 respondents: 400 respondents 12 to 19 year old by sex and 850 respondents 20 to 79 year old by sex.

For the NNK metabolites subsample, respondents 12 to 79 year old attending the MEC are randomly selected according to their smoker status (smoker, non-smoker exposed to smoke and non-smoker not exposed to smoke) to be included or excluded from this subsample. The targeted subsample size is 2,500 respondents.

Data sources

Data collection for this reference period: 2016-01-04 to 2017-12-20

Responding to this survey is voluntary.

Data are collected directly from survey respondents.

Collection includes a combination of a personal interview using a computer-assisted interviewing method and, for the physical measures, a visit to a mobile examination centre (MEC) specifically designed for the survey.

The CHMS will collect data in 16 sites across the country. The collection sites are located in seven provinces: Prince Edward Island, New Brunswick, Quebec, Ontario, Saskatchewan, Alberta and British Columbia. Collection is scheduled so that each region is distributed within the two-year collection period, distributed between seasons and in a way that tries to minimize the movement of staff and equipment between sites. The CHMS MEC stays in each site for five to seven weeks, collecting direct measures from approximately 350 respondents per site.

First step: personal interview at the household

The first contact with respondents is a letter sent through the mail. The letter informs people living at the sampled address that an interviewer will visit their home to collect some information about the household.

At the home, the application randomly selects one or two respondents and the interviewer conducts a separate health interview with each of them. The interview takes 45 to 60 minutes per respondent. The interviewer then assists the respondent in setting an appointment for the physical measures at the CHMS MEC.

Second step: visit to the CHMS MEC

Statistics Canada uses MECs to conduct the physical measures portion of the survey. Similar MECs have been used successfully for years by the National Health and Nutrition Examination Survey (NHANES) in the United States.

The MEC consists of three trailers (side by side), linked by enclosed pedestrian walkways. One trailer serves as a reception and administration area, the second trailer contains a laboratory and physical measure rooms, while the third trailer contains additional physical measure rooms.

For each respondent, the complete visit to the MEC lasts about two hours. This is an approximate time, given that each respondent is assessed for their suitability for each measure and tested accordingly.

For children under 14 years of age, a parent or legal guardian has to be present with the child at the MEC and has to provide written consent for the child to participate in the tests.

At the end of their visit to the MEC, respondents are provided with a waterproof activity monitor. This small device is worn for a week at all times except when sleeping - even when swimming or bathing. It records information about normal physical activity patterns without the respondents having to do anything special.

Respondents are also provided with materials to send a second urine sample from home to a laboratory for nutritional analysis.

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

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.

Documentation

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