2019/08/06 by Parminder Raina, Christina Wolfson, Susan Kirkland +30 · 5 citations
Health Professions · Social Sciences · #Global Health Care Issues #Health disparities and outcomes #Migration, Aging, and Tourism Studies
paper · pdf · doi:10.1093/ije/dyz173
openalex publication_date 2019/08/06 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
The Canadian Longitudinal Study on Aging (CLSA) was established to understand and address the needs of an aging population.1–3 Overall aims are to examine aging as a dynamic process; to investigate the inter-relationship among intrinsic and extrinsic factors from mid-life to older age; and to capture the transitions, trajectories and profiles of aging.4 A central objective in creating the CLSA was to provide national infrastructure and build capacity for state-of-the-art, interdisciplinary, population-based research and evidence-based decision-making.5,6 The CLSA was designed to be a national, longitudinal research platform that includes participants from all 10 Canadian provinces, and collects comprehensive data and biological samples that will support a wide variety of aging-related research questions.3 The cohort of 51 338 participants, aged 45–85 years at enrolment, is composed of two complementary cohorts that may be studied separately or together: (1) the Tracking cohort of 21 241 participants randomly selected from within all 10 provinces who are interviewed by telephone, and (2) the Comprehensive cohort of 30 097 participants randomly selected from within 25–50 km of 11 data collection sites (DCSs) (in seven provinces) who are interviewed in person, take part in in-depth physical assessments at DCSs, and provide blood and urine samples. To support research that integrates the two cohorts, a common set of questionnaire information is being collected for both the Tracking and Comprehensive cohorts, and the same core data and data collection are planned for each future follow-up for both cohorts. All participants will be followed-up every 3 years after baseline until 2033 or until death. Recruitment and baseline data collection were completed in 2015, and the first follow-up was completed in mid-2018. Figure 14 shows an overview of the CLSA design. CLSA data collection timeline. The CLSA cohort is a national stratified sample of 51 338 women and men aged 45–85 years at the time of recruitment. The inclusion of study participants as young as 45 years of age was motivated by the desire to capture mid-life experiences, since important changes known to influence outcomes later in life occur during this period.7,8 The lower age limit at the baseline also allowed inclusion of a sample from the baby boom cohort (i.e. those born between 1946 and 1964) that will constitute a significant percentage of older adults in the coming years.9,10 The upper age limit was set to keep the focus on adults who have reached old age living in the community. One of the interests in studying the oldest age group prospectively is to examine transitions into the final years of life. Participation in the CLSA cohort is voluntary and all individuals provided written informed consent.3 The selection and recruitment process is detailed elsewhere,3,11 but in brief, a random sample of eligible households was contacted, and if an eligible individual in the household was identified, they were asked to provide their information to the CLSA in order to be contacted for recruitment. Those who responded by providing their contact information were considered pre-recruits. These pre-recruits were then contacted, and those who underwent all required baseline interviews and assessments and provided written informed consent were enrolled into the cohort. The participation rate into the CLSA was about 45% with an overall response rate of 10%. In the Tracking cohort, participants were recruited across the 10 provinces, and all questionnaire measures are collected by computer-assisted telephone interviews (CATI) administered through CLSA CATI sites established in four regions across Canada to accommodate different time zones and language (English or French) requirements for questionnaire administration. In the Comprehensive cohort, recruits were drawn from individuals living within 25–50 km (depending on the city and accessibility) of one of eleven purpose-built DCSs located in seven provinces. DCSs are located in small, medium and large cities, and several include large rural catchment areas. Comprehensive cohort participants provide data through in-person home interview [computer-assisted personal interview (CAPI)], and additional questionnaires, tests, physical measurements and biological specimens (blood and urine) that are collected at the DCS. To participate in the Comprehensive cohort, participants had to complete an in-home interview and the visit to the DCS at baseline. However, the provision of the biological specimens or their health card number for data linkage was optional. Three sampling frames were used for recruitment into the CLSA cohort: (1) recruitment from a subset of participants in the Statistics Canada’s Canadian Community Health Survey-Healthy Aging (CCHS-HA); (2) recruitment from the registries of provincial health care systems; and (3) recruitment using Random Digit Dialing (RDD) of landline telephones. Since people with less education and lower socio-economic status are often under-represented in population-based studies,12–14 efforts were made to oversample certain areas identified using census data to ensure these groups are represented in the CLSA. Sampling weights were calculated for the combined cohort, as well as for the Tracking and Comprehensive cohorts.11 Since the CCHS-HA was a nationally representative sample of Canadians >45 years of age with a response rate of >80%, it was used as the first sampling frame for the selection of the CLSA cohort and therefore, the same eligibility criteria were applied to all sampling frames to ensure consistency.15 Similar to CCHS-HA, the CLSA excludes residents of the Canadian territories and some remote regions, persons on Federal First Nations reserves and other provincial First Nations settlements, full-time members of the Canadian Armed Forces, and institutionalized persons (including long-term care). In addition to these exclusion criteria, participants had to be able to complete the interviews in English or French and be physically and cognitively able to participate on their own (e.g. able to hear, able to answer).3 Participants who become institutionalized after baseline will continue to be followed until study completion, death or loss to follow-up. Given the diversity of goals for the research platform and the statistical models used for these effects and estimates, as well as those of future (and as yet unknown) research questions, it was difficult to provide globally meaningful effect sizes for sample-size calculations. Consequently, one strategy used to determine CLSA sample size was to carry out simulations based on projected evolutions of the cohort experience over time, similar to a strategy used by the UK Biobank.16 For these simulations, the prevalence of selected exposures and the incidence of selected outcomes, such as particular chronic diseases, over the period of follow-up were used as a guide to assess the adequacy of the proposed sample size. First, the expected number of cases of an outcome was simulated for each 3-year wave of the CLSA based on sex- and age-specific incidence rates and taking into account the aging of the cohort over time. The simulations also accounted for mortality (based on age- and sex-specific annual mortality rates from Statistics Canada) and attrition due to loss to follow-up [estimated at 0.5% per year based on the attrition rates for the National Population Health Survey (1994–95 to 2000–01)].17,18 For example, for a condition with a high annual incidence rate, such as hypertension (sex- and age-specific incidence rates ranging from 31 to 43 cases/1000 persons per year19), we would expect almost 1516 cases from a cohort of 20 000 people and 2273 cases from a cohort of 30 000 people (at the end of baseline data collection). We also investigated the adequacy of the power profiles for two types of outcomes: hazard ratios (for incidence studies) and odds ratios (for nested case-control studies) using an iterative simulation-based approach. Because the Comprehensive cohort includes physical measures and biological specimens that may be relevant to many analyses, we wanted to examine the power using just this cohort as well as the full CLSA sample. Simulations were undertaken to determine the minimum detectable hazard ratio (MDHR) for the Comprehensive cohort (n = 30 000) and the minimal detectable odds ratio (MDOR) for the combined cohort (n = 50 000). The results of these simulations demonstrate the robustness of the CLSA data to power a wide variety of associations.17 Selected weighted demographic and social characteristics of CLSA participants at baseline were compared with those of the CCHS-HA and Statistics Canada Census 2011 (see Table 1). These comparisons suggest that the weighted CLSA data are generalizable to the comparable Canadian population on many key variables. As discussed above, the CCHS-HA (2008–09) was an initial source of participants for the CLSA Tracking cohort, with a subset of CCHS-HA participants (56%) agreeing to be contacted by the CLSA for possible recruitment.18,20 Approximately 20% of CCHS-HA participants were also CLSA participants. We conducted a sensitivity analysis by removing participants that overlapped between CCHS-HA and CLSA, and the results, with and without overlap, were not significantly different (data not shown). Therefore, we present only the comparison with the full CCHS-HA. It is important to note that the results presented in Table 1 are based on sampling inflation weights, and three distinct inflation sampling weights were used to calculate descriptive results for the Tracking, Comprehensive and overall cohorts respectively. Selected socio-demographic, lifestyle and health status characteristics of CLSA participants (n, Tracking = 21 241, Comprehensive = 30 097, combined = 51 338) compared with CCHS Healthy Aging (n = 20 087) and Canadian Census 2011 data A subset of the CCHS-HA participants allowed contact by the CLSA for possible recruitment into the Tracking cohort. Therefore, a selection (approximately 20%) of CCHS-HA participants are also participants of the CLSA. The sensitivity analysis was done by excluding this 20% of participants from the CCHS-HA. Canadian Census 2011 [in 2011, the National Household Survey (Long-form) of the Canadian Census was done on a random sample of Canadians]. CLSA, Canadian Longitudinal Study on Aging.CCHS-HA, Canadian Community Health Survey-Healthy Aging. NA, Not applicable. Selected socio-demographic, lifestyle and health status characteristics of CLSA participants (n, Tracking = 21 241, Comprehensive = 30 097, combined = 51 338) compared with CCHS Healthy Aging (n = 20 087) and Canadian Census 2011 data A subset of the CCHS-HA participants allowed contact by the CLSA for possible recruitment into the Tracking cohort. Therefore, a selection (approximately 20%) of CCHS-HA participants are also participants of the CLSA. The sensitivity analysis was done by excluding this 20% of participants from the CCHS-HA. Canadian Census 2011 [in 2011, the National Household Survey (Long-form) of the Canadian Census was done on a random sample of Canadians]. CLSA, Canadian Longitudinal Study on Aging.CCHS-HA, Canadian Community Health Survey-Healthy Aging. NA, Not applicable. Though generalizable to the Canadian population on many important variables, some differences exist between the CLSA participants’ characteristics and CCHS-HA participants (Table 1). The CLSA Comprehensive cohort, in particular, are more educated, have higher household income, have higher percentages of participants who are Canadian born and rate their general health as very good. By design, the Comprehensive cohort was recruited from an area 25–50 km from a DCS and included small urban areas with rural populations, medium size urban areas and large cities respectively. The weighted data for the Comprehensive cohort alone, thus, reflects only these regions and not the 10 provinces of Canada. Participation in the Comprehensive cohort required a commitment to a significant amount of time and effort to provide data. These factors, along with the voluntary nature of participation in the CLSA, may have contributed to the differences between the Comprehensive cohort, CCHS-HA and Census data. The Tracking Cohort, especially with its links to the CCHS-HA, was more similar to the CCHS-HA and Census 2011. In longitudinal studies, one of the main challenges is participant engagement and retention.12,21 Barriers to participant retention include: (1) participants moving from their enrollment location; (2) participants developing health-related barriers; (3) participants experiencing cognitive decline; (4) participants entering long-term care; and (5) participants withdrawing due to study fatigue or associated reasons. In response to these barriers, CLSA accommodation and participant retention strategies were developed. Every attempt is made to continue to follow each participant over time as they change geographic locations. For the Tracking cohort, this requires being able to continue to administer questionnaires by phone. For the Comprehensive cohort, those who move into an area covered by another DCS are re-assigned to the new DCS and undergo follow-up as usual. If the participant has moved out of range of all eleven DCSs, then we complete the data collection using a telephone-based survey (called the DCS by phone). Since the placement of DCSs covers many of the Canadian urban population areas, we expected to be able to re-assign many participants to a new DCS. At the time of data collection, participants experiencing hearing impairment, speech/language problems or vision loss are offered accommodations, as required, in the interview. Procedures and processes have been developed to identify the appropriate accommodations, such as involving a helper (e.g. allowing a spouse to be present during survey questions if they can assist in enunciating or communicating for a participant with hearing loss) or declining a test for specific measures (e.g. physical function measures when a participant cannot safely stand). Under exceptional circumstances, modified interviews have been developed to facilitate participation. A ‘DCS at home’ interview replaces a DCS visit. This is meant to be used when a participant is physically unable to attend a DCS location. This accommodation contains as much content from a regular DCS visit as is possible. An ‘in-home by phone’ and ‘DCS by phone’ interview collects only the questionnaire content via telephone interview. These interviews are meant to accommodate participants where an in-home or DCS visit is not feasible. The proportion of participants who required accommodations at follow-up was small. One of the potential barriers to continued participation is decline in cognitive abilities. Individuals at highest risk of cognitive decline are those ≥70 years of age, which allows us to identify those participants who may need a proxy decision maker proxy information Participants who were ≥70 years of age at and participants who at each are asked to they would to participate in the CLSA in the future they become unable to provide their own If they that they would to continue in the CLSA, they are asked to provide consent for the CLSA to contact an identified proxy to assist in providing the need in the In such the contact information of a proxy decision maker and proxy information often the same person, is a CLSA participant into an long-term care or we continue to attempt to follow using the accommodation strategies for for health-related barriers or for cognitive as Participants who into and continue to be considered to the longitudinal of the CLSA, effort has been made to participants in order to keep motivated to continue in the using contact social and participant engagement are being by the CLSA and in with the CLSA and DCS By the end of the first of participants had from data of those to continue data collection through data Participants who to be were more often had lower of and education and general An additional of participants since their baseline This includes in the Tracking cohort and in the Comprehensive cohort. a questionnaire is administered to a or after a participant The CLSA questionnaire is designed to information on the and of the of transitions and health care for the 3 to death. is also on the questionnaire of the of and death of the The CLSA was in with to understand the of health outcomes, lifestyle and and social measures in and to the of the aging process were on questions that only be with a longitudinal and were when This included of time, across age or required and of in English and in All measures are on the CLSA Table the and measures collected in the CLSA. of measures in the CLSA For a detailed of specific measures and the and visit the CLSA at from The Canadian Longitudinal Study on Aging (CLSA) on Health and Aging in from of measures in the CLSA For a detailed of specific measures and the and visit the CLSA at from The Canadian Longitudinal Study on Aging (CLSA) on Health and Aging in from is a core set of measures that are common across the Tracking cohort and the Comprehensive These measures an set of social and demographic health status and lifestyle and measures and health care We measures where in French or English or established questionnaires from other national such as Statistics Canada’s Canadian Community Health Survey A number of cognitive measures to address and function are administered to all CLSA these include the 1 and the and the measures that are administered to the Comprehensive cohort participants the and and are part of the questionnaires for all participants, and information that is more detailed is collected from Comprehensive cohort participants, an in-person of during the in-home visit and an in-depth during the DCS visit. assessments are conducted only for the Comprehensive cohort, as a part of the DCS visit. include as well as assessments for physical vision and In participants undergo an an of using and a for and and and By many of the physical measures important for in-person hearing and physical are also collected via in the the 30 097 participants in the baseline Comprehensive cohort, and provided blood and urine samples respectively. Approximately of blood is collected into types to types four types of and two types of blood and without and three types of blood blood collection and in the purpose-built at each DCS. samples are within of collection and to for urine from collection for a of are at in to the CLSA and for long-term in The core set of that have been to are in Table of in the CLSA at each wave of the for follow-up. All will be completed by from The Canadian Longitudinal Study on Aging (CLSA) on Health and Aging in from of in the CLSA at each wave of the for follow-up. All will be completed by from The Canadian Longitudinal Study on Aging (CLSA) on Health and Aging in from At the time of participants were asked to provide their health number if they to linkage of their CLSA data to their in health care The of these potential is to information on health and and as well as to and of death. of participants provided CLSA with their health Table 1 an overview of socio-demographic, lifestyle and health status characteristics of the CLSA participants at baseline. the combined cohort, were or living with a are and or general or are and are regular The CLSA on Health and Aging in from a detailed of the key of the The of the CLSA is to facilitate important and research on health and and to health and to the of aging data are for and through a data from the first follow-up was made in of of all are on the CLSA at have in in a variety of areas, and links to can be on the CLSA at The and of data in the CLSA the of and areas that are not in or proposed of aging in Canada or The CLSA includes participants from age 45 at those included in aging This the of prospectively that may be associated with changes in health later in life. At the other end of the age the CLSA includes participants at baseline aged One of the interests in studying the oldest age group prospectively is to examine transitions into and in the final years of life. The CLSA was designed as a platform to build capacity for research on the many factors that aging over the life The longitudinal of the CLSA the and study of health transitions and A of the CLSA is to support research into the and of the of risk factors, which will to that health as they sampling may be it is that due to cohort to and participants. To be enrolled in the CLSA, participants had to provide written The participants were required to complete French or English language interviews by telephone and Comprehensive cohort participants were required to have an in-home visit and a DCS visit. 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The CLSA is one of the comprehensive research for aging research The recruitment and baseline data collection on 51 338 men and women aged 45–85 between 2011 and data collection a new wave of follow-up data every 3 The CLSA collects information on the lifestyle and of These factors are being studied to understand and in they both the of health and the of and as people collected includes survey information on social and demographic health and function on all participants, and physical measures and for over 30 000 of the participants as part of the Comprehensive cohort. The data collection for the first follow-up wave was completed in and the follow-up wave in on the CLSA and on to the is on the CLSA at The Canadian of Health is the of the CLSA. The infrastructure that the CLSA was by the Canada for provincial and 11 research for the baseline and first follow-up assessments was from the Health of Health the of Health and and the of We would to the to the of and a 1 Canada in and the and in and for Aging. is by and by the in Population and of