Canadian Longitudinal Study on Aging: Platform for studying the epidemiology of the COVID-19 pandemic in aging populations [CLSA, study data contributed to the CITF Databank]

<b>Background:</b> As an established ongoing population-based cohort of over fifty thousand Canadians, the Canadian Longitudinal Study on Aging (CLSA) offered an opportunity to rapidly study COVID-19 immunity in Canada’s aging population. <br>

<b>Aims of the CITF co-funded study:</b> CLSA COVID-19 study aimed to measure SARS-CoV-2 seroprevalence and seroconversion among older adults across Canada by province, age, and sex in the first two years of the pandemic (2020 and 2021). They also aimed to better understand the symptoms, risk factors, and impacts of COVID-19 through questionnaires. <br>

<b>Methods:</b>The CLSA cohort study enrolled participants aged 45-85 across Canada via random digit dialling. Participants in the tracking cohort comprised a representative sample of Canadians, who completed cognitive tests and answered questionnaires via telephone interview at baseline and at two follow-ups. Those in the comprehensive cohort were selected from a random sample of Canadians, and participated in an at-home physical exam, answered questionnaires, completed cognitive tests, and provided blood and urine samples at baseline and two follow-ups. For participants aged 55-80 in this cohort, they completed repeated cognitive testing and brain scans for brain health surveillance. Participants in all cohorts provided a blood sample for COVID-19 antibody testing and completed a COVID-19 questionnaire. Each participant was contacted every 3 years and was followed for at least 20 years or until death.<br>

<b>Summary of the contributed data:</b> The datasets include 19,334 participants who completed baseline surveys between October 2020 and August 2021. 23% of participants gave one or more blood samples between October 2020 and July 2021 for analysis. A total of 4,365 samples were collected. Variables include data in the following areas of information: demographics (age, gender, race-ethnicity and indigeneity, province, household composition, education), general health (smokes, chronic conditions, height and weight, flu vaccine), exposure risk factors (occupation, travel history, adherence to COVID-19 public health guidelines), COVID infection history (positive tests, symptoms, hospitalizations), SARS-CoV-2 vaccination, and qualitative serology (antibodies against SARS-CoV-2 nucleocapsid and spike proteins).