Cohort study
● Cohort=same alikeness
● Follow up
● Two main types
○ Prospective
■ Using data that I have retrieved from this study
■ No other data were given beforehand
○ Retrospective
■ Using data that was given beforehand
Aspect
Prospective Cohort
Retrospective Cohort
Timeframe
Follows participants into the future
Existing records from the past.
Also follow them continuously
Exposure
Measured at the start, before outcomes
occur
Measured from past records
Outcome
Occurs after enrollment
Outcome may have already
occurred
Example
Physical activity & diabetes
Asbestos exposure & lung cancer
Prospective Cohort study
Physical activity and risk of T2 Diabetes: 10 Year cohort study
Participants
Participants are chosen before developing on diabetes (outcome), they are followed through the
study
These participants does not have diabetes yet, but are at risk group
Exposure
With self reported physical activity baseline…
● High
● Moderate (60~150 min)
● Low(less than hour)
Follow up
10 years study
Annual health assessments are done and questionnaires were given out to identify T2 diabetes Retrospective Cohort Study
Occupational Asbestos Exposure and lung cancer risk
Evaluate how would past exposure on asbestos will associate with lung cancer
Population
2,000 factory workers in 1970-1990 Ontario. This group would have been exposed to asbestos
Exposure
Historical job records, environmental assessments
Followup
Lung cancer incidence tracked from 1990 onward (using health records)
Here we have already had data of workers at risk by exposure to asbestos.