What’s Available?

Questionnaire data | Biosamples and physical measures | Additional data collection | Fast Facts About the Cohort

Questionnaire Data

  • Baseline questionnaire completed by about 225,000 participants
  • More than 930 variables describing social and economic demographics, personal and family health histories, medications, sleep patterns, alcohol and tobacco use, physical activity and environmental exposures.
  • Regular follow-up questionnaires will be conducted to track changes in overall health

Ontario Health Study Baseline Questionnaire (PDF)

The OHS concluded its first follow up questionnaire in March 2018. The questionnaire asked participants to provide an update on their health. It also had additional questions around e-cigarettes and marijuana use, mental health and over-the-counter drugs.

Ontario Health Study Follow-up Questionnaire (PDF)

Biosamples and Physical Measures

  • Non-fasting blood samples were collected from more than 41,000 participants.
  • 1,000 samples have been genotyped through a Canadian Partnership for Tomorrow Project using the UKBIObank Affymetrix arrays. Inflammatory markers will be assayed for a subset, including cytokine panels.
  • The repository holds serum, plasma, red blood cells and buffy coat.
  • For a subset of participants, (~6,000) there are lymphocytes in DMSO
  • Urine samples and physical measures were collected from 12,600 and 13,400 participants respectively. Physical measures include anthropometrics, blood pressure, resting heart rate, body fat percentage, grip strength and spirometry.

Physical measures and blood samples were collected through a variety of Study initiatives:

Regional assessment centres:

Located in Mississauga, Owen Sound and Sudbury, men and women regardless of their health history were enrolled and invited to the nearest centre where they completed self- and interviewer-administered questionnaires, provided a number of physical measures and provided blood and urine samples. The assessment centres opened in 2009 and closed in July 2010. Approximately 7,600 participants were recruited.

Toronto assessment centre:

Starting in 2013, a subset of participants visited an assessment centre in downtown Toronto and provided a series physical measures, completes a computerized cognitive battery, and provided blood and urine samples. Participants also had the opportunity to participate in a home sleep study. This centre was closed March 2014.

Local study centres:

The OHS hosted a series of temporary blood collection clinics in communities across the province. More than 50 clinics were held from summer 2014 until March 2017.

LifeLabs blood collection program:

Through a partnership with LifeLabs Medical Laboratories, participants were able to provide samples at LifeLabs locations across Ontario. This program ran until March 2017.

Additional Data Collection

  • The Ontario Sleep Study collects accelerometry and sleep respiratory function from approximately 2,000 participants.
  • The Canadian Alliance for Healthy Hearts and Minds has collected MRIs, and conducted Food Frequency Questionnaires and cognitive assessments from approximately 2,900 participants.

Fast Facts about the OHS Cohort

Participant Demographics


Age Distribution:

Age distribution

Sex Distribution:

Sex distribution

Participant-Reported Prevalence of Chronic Disease

Chronic Disease Prevalence

Participant-Reported Prevalence of Common Cancers Ranked by Nationwide Prevalence

Cancer Prevalence