Cohort Profile Update: The Québec Birth Cohort on Immunity and Health (CO·MMUNITY)

The Quebec Birth Cohort on Immunity and Health was originally set up to investigate the non-specific effects of Bacillus Calmette-Guerin (BCG) vaccination on the occurrence of selected autoimmune and inflammatory diseases and included 81 496 persons born in 1974, who were followed until 1994. The cohort was expanded to enable studying rarer diseases requiring a larger sample size and follow-up during adulthood. Assembled in 2017, the expanded Quebec Birth Cohort on Immunity and Health (CO·MMUNITY) includes 400 611 individuals born in 1970–74 in the province of Quebec, Canada, and followed until 2014; 2% of the cohort are deceased and 10% were potentially lost to follow-up. Administrative data acquired cover perinatal and sociodemographic information, BCG vaccination, medical services, hospitalizations for diabetes, lymphoma, multiple sclerosis, inflammatory bowel disease, asthma and other allergic diseases, prescription drugs and death if applicable. A nested case-control study on inflammatory bowel disease was conducted with 2728 participants. Although our work is governed by data privacy considerations, we welcome new collaboration opportunities. Please address enquiries to Marie-Claude Rousseau [[email protected]]. The overarching aim of the Quebec Birth Cohort on Immunity and Health, established in 2010, was to assess the occurrence of autoimmune and inflammatory diseases in relation to a non-specific stimulation of the immune function in early age, resulting from Bacillus Calmette-Guerin (BCG) vaccination.1 It was originally set up to estimate the association of BCG vaccination with childhood diabetes and asthma. All individuals born in the province of Quebec, Canada, in 1974 after at least 32 weeks of gestation were eligible. Probabilistic linkage allowed the merging of data from the Birth Registry and the Healthcare Registration File, constituting the cohort base.1 Data were obtained from the Quebec BCG vaccination registry and administrative health databases. In total, 81 496 individuals were successfully linked and included in the cohort (90.5% of those who were eligible). Data were extracted until 1994 and included sociodemographic characteristics, vital status and use of health services for asthma, allergic diseases and diabetes. Validated algorithms were applied to identify disease incidence based on administrative health data. Additional data on potential confounders of the association between BCG vaccination and asthma were collected using a two-stage sampling approach with a balanced design (Survey on Childhood Environment and Allergic Diseases, 2012).2 Equal numbers of participants were randomly sampled among four groups defined by BCG vaccination (yes/no) and asthma status (yes/no). Information collected from the 1643 participants included sociodemographic, perinatal, environmental and health- and immunization-related factors unavailable in administrative databases.1–3 The original birth cohort was expanded by adding about 320 000 individuals, and the follow-up lengthened by 20 years, to enable studying other, rarer, inflammatory, autoimmune, metabolic and infectious diseases requiring a larger sample size and follow-up during adulthood. The new focus for the expanded Quebec Birth Cohort on Immunity and Health (CO·MMUNITY) is on studying the associations between BCG vaccination and lymphoma, multiple sclerosis and inflammatory bowel disease, and allowing novel analyses on diabetes and asthma. In addition to providing a larger sample size, the updated cohort enables a new focus on early adulthood (up to 40–44 years of age), specific phenotypes of diabetes and multiple sclerosis based on medication use, potential risk or protective factors for these diseases and patterns of health services use. We are further broadening the scope of CO·MMUNITY to study the long-term associations between BCG vaccination and mortality, as well as incidence of bacterial and viral infectious diseases, including COVID-19. This will enable us to continue addressing important gaps in knowledge about the non-specific effects of BCG vaccination. Given the absence of a unique identification number, a probabilistic record linkage using five nominal identifiers (surname and given name, date of birth, sex, father’s given name) was realized between the Birth Registry and the Healthcare Registration File. This process estimates an overall matching weight for each pair of records, based on agreement and data frequency.4 Then, pairs with weights below a lower threshold are rejected, those with weights above an upper threshold are linked, and pairs with in between matching weights are evaluated manually. The linkage was conducted with the Generalized Record Linkage System and the G-Link v2.4 software, both developed by Statistics Canada.5 CO·MMUNITY includes persons born in the province of Quebec, Canada, from 1 January 1970, to 31 December 1974, after at least 32 weeks of gestation. Of the 443 045 individuals meeting these inclusion criteria, the probabilistic record linkage was successful for 400 611 persons, representing 90.4% of those who were initially eligible in the provincial population, fostering high representativeness (Figure 1). There were no substantial differences between the cohort and the provincial population in terms of sociodemographic or perinatal characteristics. The proportion of deceased individuals was 2% in the cohort, compared with 3% in the provincial population, indicating that some deceased individuals may have been missed. This is likely due to the archiving of their data during an update of the health care data management system in 1996–97. The expanded Quebec Birth Cohort on Immunity and Health (CO·MMUNITY): overview of record linkage and data sources. Adapted from Rousseau et al.1 Compilation based on data from the ©Government of Quebec, Statistics Quebec, 2017. Statistics Quebec is not responsible for compilations or interpretation of results. BCG, Bacillus Calmette-Guérin; CO·MMUNITY, expanded Quebec Birth Cohort on Immunity and Health; INRS, Institut National de la Recherche Scientifique; ISQ, Institut de la Statistique du Québec (Statistics Quebec); MED-ECHO, Maintenance et Exploitation des Données pour l’Étude de la Clientèle Hospitalière (Meta-data on hospitalizations from the public health care provider); MSSS, Ministère de la Santé et des Services Sociaux (Ministry of Health and Social Services); RAMQ, Régie de l’Assurance Maladie du Québec (public health care provider). Administrative databases are indicated by a white background and datasets based on self-reported information are depicted with grey shading In 2021, we also conducted a case-control study, nested within CO·MMUNITY: the Life History Intestinal Health Study. Persons identified with Crohn’s disease or ulcerative colitis using validated algorithms based on administrative health data,6,,7 and a random sample of potential controls, were invited to participate. Response rates were 47% (n = 946), 52% (n = 1212) and 55% (n = 570), respectively, among controls, cases of Crohn’s disease and cases of ulcerative colitis. There were two sources of data for subjects in CO·MMUNITY: (i) follow-up through data extraction from administrative sociodemographic and health databases; and (ii) self-reported information among subgroups, including the Life History Intestinal Health Study (M.-C.R. and P.J., manuscript in preparation). The cohort establishment and subsequent analyses were approved by the Commission of Access to Information (Commission d’Accès à l’Information du Québec), the governmental body overseeing access to and protection of personal information, and the research ethics committees of Institut National de la Recherche Scientifique (INRS) and Statistics Quebec. As previously described,1 perinatal and sociodemographic information was extracted from the Birth Registry. Data on BCG vaccination were retrieved from the provincial registry. CO·MMUNITY will allow addressing hypotheses on the long-term non-specific effects of BCG vaccination, for which some features of the Quebec BCG vaccination programme provide important advantages. The cost of the vaccine was paid by the public health system, but vaccination was not compulsory. As a result, a large enough proportion of the population remained unvaccinated, allowing sufficiently large numbers of persons in the unexposed group. Regional differences in BCG vaccination rates seemed to depend on organizational factors rather than on individual preferences for or against BCG vaccination.8 Self-selection for BCG vaccination is thus unlikely to bias the associations of interest. Other data acquired from administrative databases included physician and prescription drug claims, hospitalizations and date and cause of death, if applicable. In CO·MMUNITY, the administrative health data were expanded by 20 years (until 31 December 2014) and included information on previous and new diseases of interest. Table 1 provides an overview of the type of information extracted from the birth and death registries, health care registration file, prescription drug claims, physician claims, hospitalization data, Quebec Cancer Registry, Quebec BCG vaccination registry and the Canadian Census. Data acquired from administrative sociodemographics, health databases and the Canadian Census available in CO·MMUNITY, 1970–2014 Adapted from Rousseau et al.1 AHFS, American Hospital Formulary Service; BCG, Bacillus Calmette-Guerin; CO·MMUNITY, expanded Quebec Birth Cohort on Immunity and Health; ICD-9, International Classification of Diseases—9th Revision; ICD-10, International Classification of Diseases—10th Revision; INRS, Institut National de la Recherche Scientifique; MED-ECHO, Maintenance et Exploitation des Données pour l’Etude de la Clientèle Hospitalière (Meta-data on hospitalizations from the public health care provider); MSSS, Ministère de la Santé et des Services Sociaux (Ministry of Health and Social Services); RAMQ, Régie de l’Assurance Maladie du Québec (Québec Public Health Insurance). Data acquired from administrative sociodemographics, health databases and the Canadian Census available in CO·MMUNITY, 1970–2014 Adapted from Rousseau et al.1 AHFS, American Hospital Formulary Service; BCG, Bacillus Calmette-Guerin; CO·MMUNITY, expanded Quebec Birth Cohort on Immunity and Health; ICD-9, International Classification of Diseases—9th Revision; ICD-10, International Classification of Diseases—10th Revision; INRS, Institut National de la Recherche Scientifique; MED-ECHO, Maintenance et Exploitation des Données pour l’Etude de la Clientèle Hospitalière (Meta-data on hospitalizations from the public health care provider); MSSS, Ministère de la Santé et des Services Sociaux (Ministry of Health and Social Services); RAMQ, Régie de l’Assurance Maladie du Québec (Québec Public Health Insurance). Table 2 presents a summary of the data collected among 2728 participants in the Life History Intestinal Health Study, 2021. The information included sociodemographic characteristics, diet (including alcohol, tea and coffee consumption), physical activity, and environmental, health-related and psychosocial factors over the life course. Data collected in the nested case-control study—Life History Intestinal Health Study, 2021 Adapted from Rousseau et al.1 Silhouettes for children27 and adults28 used with the authors’ authorizations and validated for use in epidemiological studies.29,,30 Inspired by Hosking et al.’s Lifetime Diet Questionnaire.31 Inspired by the Godin-Shepard Leisure-Time Exercise Questionnaire.32,,33 Adapted from the Canadian Community Health Survey.34 Adapted from the Women’s Interview Study of Health Questionnaire.35,,36 Inspired by the Social Readjustment Rating Scale.37 Data collected in the nested case-control study—Life History Intestinal Health Study, 2021 Adapted from Rousseau et al.1 Silhouettes for children27 and adults28 used with the authors’ authorizations and validated for use in epidemiological studies.29,,30 Inspired by Hosking et al.’s Lifetime Diet Questionnaire.31 Inspired by the Godin-Shepard Leisure-Time Exercise Questionnaire.32,,33 Adapted from the Canadian Community Health Survey.34 Adapted from the Women’s Interview Study of Health Questionnaire.35,,36 Inspired by the Social Readjustment Rating Scale.37 Characteristics of the CO·MMUNITY study population are shown in Table 3. The CO·MMUNITY subjects were distributed equally in each birth year (1970–74), and half were men (51%). Most subjects had Quebec-born parents (88% of the subjects’ mothers and 87% of their fathers); 46% of the cohort subjects were vaccinated with BCG, 88% (156 513/178 352) in the first year of life. After the exclusion of persons who died over the follow-up (n = 7894) and those who may have been lost to follow-up (n = 38 814), defined as such due to missing yearly postal codes for ≥5 years likely indicating temporary or permanent emigration, the characteristics of the remaining subjects are similar to those of the baseline study population. The only minor differences are 2% increases in the proportions of subjects with parents born in Quebec and of those who received the BCG vaccine. At the end of follow-up in 2014, subjects were aged 40–44 years. Characteristics of the CO·MMUNITY study population (1970–2014) at baseline and end of follow-up in 2014 Compilation based on data from the ©Government of Quebec, Statistics Quebec, 2017. Statistics Quebec is not responsible for compilations or interpretation of results. BCG, Bacillus Calmette-Guerin; CO·MMUNITY, expanded Quebec Birth Cohort on Immunity and Health. All cohort members, excluding those who were deceased over the follow-up and those who had a missing postal code for a minimum of 5 years at the end of follow-up (considered as possibly lost due to emigration). Birthweight: extremely low (<1000 g), very low (1000 to <1500 g), low (1500 to <2500 g), normal (2500 to ≤4200 g), and high (>4200 g). Gestational age: premature (<37 weeks), at term (37–41 weeks) and post-term (>41 weeks). Determined using the second character of the subjects’ postal code in 1987 (0: rural, ≠0: urban). Estimated by ‘median household income’ from the 1991 Canadian census using the first three characters of subjects’ postal code. Characteristics of the CO·MMUNITY study population (1970–2014) at baseline and end of follow-up in 2014 Compilation based on data from the ©Government of Quebec, Statistics Quebec, 2017. Statistics Quebec is not responsible for compilations or interpretation of results. BCG, Bacillus Calmette-Guerin; CO·MMUNITY, expanded Quebec Birth Cohort on Immunity and Health. All cohort members, excluding those who were deceased over the follow-up and those who had a missing postal code for a minimum of 5 years at the end of follow-up (considered as possibly lost due to emigration). Birthweight: extremely low (<1000 g), very low (1000 to <1500 g), low (1500 to <2500 g), normal (2500 to ≤4200 g), and high (>4200 g). Gestational age: premature (<37 weeks), at term (37–41 weeks) and post-term (>41 weeks). Determined using the second character of the subjects’ postal code in 1987 (0: rural, ≠0: urban). Estimated by ‘median household income’ from the 1991 Canadian census using the first three characters of subjects’ postal code. The main outcomes under study were diabetes, lymphoma, multiple sclerosis, inflammatory bowel disease (Crohn’s disease and ulcerative colitis) and asthma. Health services for the main and other secondary outcomes were retrieved from medical service claims, prescription drugs and hospitalization data. The extracted International Classification of Diseases (ICD) codes are listed in Supplementary Table S1. Table 4 shows the algorithms applied to identify the main outcomes, and their period prevalence in CO·MMUNITY. Period prevalence of the diseases of interest based on validated algorithms applied to health services data (n = 400 563), CO·MMUNITY 1983–2014a ≥2 diabetes-related physician claims within 2 years or ≥1 diabetes-related hospitalization38 c ≥2 physician claims or hospitalizations within 2 months or listed in the Quebec Cancer Registry with a diagnosis of Hodgkin’s or non-Hodgkin’s lymphoma18 Paediatric: ≥1 sigmoidoscopy/colonoscopy and (≥4 IBD-related physician claims or 2 hospitalizations within 3 years) or 0 sigmoidoscopy/colonoscopy and (≥7 IBD-related physician claims or 3 hospitalizations within 3 years)6 Adult: ≥5 IBD-related physician claims or hospitalizations within 4 years7 ≥2 asthma-related physician claims within 2 years or ≥1 asthma-related hospitalization42,,43 ≥2 diabetes-related physician claims within 2 years or ≥1 diabetes-related hospitalization38 c ≥2 physician claims or hospitalizations within 2 months or listed in the Quebec Cancer Registry with a diagnosis of Hodgkin’s or non-Hodgkin’s lymphoma18 Paediatric: ≥1 sigmoidoscopy/colonoscopy and (≥4 IBD-related physician claims or 2 hospitalizations within 3 years) or 0 sigmoidoscopy/colonoscopy and (≥7 IBD-related physician claims or 3 hospitalizations within 3 years)6 Adult: ≥5 IBD-related physician claims or hospitalizations within 4 years7 ≥2 asthma-related physician claims within 2 years or ≥1 asthma-related hospitalization42,,43 Adapted from Rousseau et al.1 Compilation based on data from the ©Government of Quebec, Statistics Quebec, 2017. Statistics Quebec is not responsible for compilations or interpretation of results. IBD, inflammatory bowel disease; CI, confidence interval; CO·MMUNITY, expanded Quebec Birth Cohort on Immunity and Health. Given that health services were available only from 1983, 48 participants who were deceased before 1983 were excluded from these analyses. International Classification of Diseases Ninth/10th Revision/Oncology Third Revision. To exclude gestational diabetes, evidence of diabetes in women aged 10–54 years was excluded if before or after or code Period prevalence of the diseases of interest based on validated algorithms applied to health services data (n = 400 563), CO·MMUNITY 1983–2014a ≥2 diabetes-related physician claims within 2 years or ≥1 diabetes-related hospitalization38 c ≥2 physician claims or hospitalizations within 2 months or listed in the Quebec Cancer Registry with a diagnosis of Hodgkin’s or non-Hodgkin’s lymphoma18 Paediatric: ≥1 sigmoidoscopy/colonoscopy and (≥4 IBD-related physician claims or 2 hospitalizations within 3 years) or 0 sigmoidoscopy/colonoscopy and (≥7 IBD-related physician claims or 3 hospitalizations within 3 years)6 Adult: ≥5 IBD-related physician claims or hospitalizations within 4 years7 ≥2 asthma-related physician claims within 2 years or ≥1 asthma-related hospitalization42,,43 ≥2 diabetes-related physician claims within 2 years or ≥1 diabetes-related hospitalization38 c ≥2 physician claims or hospitalizations within 2 months or listed in the Quebec Cancer Registry with a diagnosis of Hodgkin’s or non-Hodgkin’s lymphoma18 Paediatric: ≥1 sigmoidoscopy/colonoscopy and (≥4 IBD-related physician claims or 2 hospitalizations within 3 years) or 0 sigmoidoscopy/colonoscopy and (≥7 IBD-related physician claims or 3 hospitalizations within 3 years)6 Adult: ≥5 IBD-related physician claims or hospitalizations within 4 years7 ≥2 asthma-related physician claims within 2 years or ≥1 asthma-related hospitalization42,,43 Adapted from Rousseau et al.1 Compilation based on data from the ©Government of Quebec, Statistics Quebec, 2017. Statistics Quebec is not responsible for compilations or interpretation of results. IBD, inflammatory bowel disease; CI, confidence interval; CO·MMUNITY, expanded Quebec Birth Cohort on Immunity and Health. Given that health services were available only from 1983, 48 participants who were deceased before 1983 were excluded from these analyses. International Classification of Diseases Ninth/10th Revision/Oncology Third Revision. To exclude gestational diabetes, evidence of diabetes in women aged 10–54 years was excluded if before or after or code our previous research on BCG vaccination and type 1 diabetes in we BCG vaccination was with the incidence of type 1 diabetes during the disease identification algorithms validated in the Quebec The risk of type 1 diabetes was similar in vaccinated compared with individuals = confidence There was no association with at vaccination, and not by evidence that BCG vaccination have a long-term on and immune in no previous study had the association between early life BCG vaccination and type type 2 and autoimmune diabetes in early adulthood. We that BCG vaccination was not with type 1 diabetes up to years of but was to a incidence at years of = BCG vaccination was with a risk of type 2 diabetes = but not with autoimmune diabetes in early adulthood = The novel use of drug to the three main phenotypes in early adulthood for the first to associations between BCG vaccination and of 1 and 2 diabetes. with follow-up in for type 2 diabetes and autoimmune diabetes in We conducted the study to date addressing the association between BCG vaccination and incidence of We identified cases of non-Hodgkin’s and Hodgkin’s with a validated by registry data. association was with non-Hodgkin’s = Hodgkin’s lymphoma, were not over thus we the to follow-up. of before years of was among vaccinated compared to individuals = After years of age, no association was = in other on BCG vaccination and multiple sclerosis not potentially by we used prescription of drugs to identify individuals with multiple association was between BCG vaccination and = multiple sclerosis of was with BCG vaccination = original the to further research based on data sources allowing the identification of such as or disease We the use of health services among persons with multiple sclerosis in a We at health services if persons were before or after years of age, which was until the at In the year persons who were had a of to a a lower of to a and a of hospitalization compared with those who were at or after years of The year after diagnosis was the period during which health services use was the and no differences by at diagnosis were in other that may the subsequent risk of inflammatory bowel disease, Crohn’s disease and ulcerative colitis. In cohort, Crohn’s disease risk was among those who had an = the was during adulthood years = This risk was in the 2 years after but not a In an association was with ulcerative colitis = which was ≥5 years compared with years after the = There are to using administrative databases for epidemiological the main the of some information on potential confounders and of data. We have the in on and on inflammatory bowel disease (M.-C.R. and P.J., manuscript in by the administrative databases with self-reported data collected from of the study population. A second to the of prescription drug claims data for a of the study population until from 1983 to public medication was only available to persons on their and persons aged of CO·MMUNITY was in In January public medication for who not have medication through and of the cohort subjects had at least period of public medication over the follow-up. A to the lower in the cohort compared with the provincial population. We that some individuals who died in their may have been due to the archiving of their data during an update of the health care data management system in 1996–97. given that CO·MMUNITY includes 90.4% of the population, is of the Quebec population. these our cohort a large sample size, population and from a and we have defined a of health outcomes using validated The addition of two of data to factors of interest and potential confounders in of the study population, cohort from based on administrative or self-reported data. an important of cohort is that BCG vaccination status is from registry This is of BCG vaccination low and may in substantial Although our work is governed by data privacy considerations, we the and of our research and are invited to the and of the study [[email protected]]. and from the and at Santé followed at The Commission of Access to Information (Commission d’Accès à l’Information du Québec), the governmental body overseeing access to and protection of personal information, the cohort establishment and subsequent analyses The research ethics committees of Statistics Quebec and of Recherche des approved the of the Supplementary data are available at the study with collaboration from and the All to the and to the and and the data. conducted the analyses. was of at Institut National de la Recherche Scientifique and were of their conducted at was of at de of the All the and approved the This work was by an from the for the Quebec of and and research from the Canadian of Health numbers de du the of the Canadian Cancer and through a with Statistics Quebec. and were by from the was by a and received from was by from and de Recherche du de de We and from Statistics Quebec, and from RAMQ, for their to of the establishment of CO·MMUNITY. We also and from Statistics Quebec for their to and data for the Life History Intestinal Health Study. We for of CO·MMUNITY as the of the updated

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