Lecture 19 - Cohort studies

Question 1

Cohort study is

Answer 1

Analytic and observational study

Question 2

Cohort study

Answer 2

Individual are defined on the basis of presence or absence of exposure to a suspected risk factor

Question 3

Steps of Cohort Studies

Answer 3

1. Identify a source population
2. Recruit your sample population (the population must not already have the outcome)
3. Assess exposure to identify which group participants belong in (exposed or non exposed)
4. Follow up over time
5. Observe whether or not participants develop the outcome
6. Calculate measures of occurrence and measure of association

Question 4

Measure of occurrence in Cohort studies

Answer 4

IR and IP

Question 5

Measure of associations

Answer 5

RR and RD

Question 6

Strength of Cohort Studies

Answer 6

• Determine temporal sequence between exposure and outcome
• Can examine multiple outcomes from an exposure
• Can calculate incidence
• Good for rare exposures

Question 7

Limitations

Answer 7

• Loss to follow up - can lead to bias id related to exposure and the outcome
• Potential for misclassification of exposure/outcomes
• Generally not good for studying rare outcome
• Time consuming
• Can be expensive

Question 8

Two types of cohort studies

Answer 8

• Prospective cohort studies (starts before exposure)
• Historical Cohort study (starts with the outcome )
  difference between them is the starting point.

Question 9

Historical cohort studies

Answer 9

• Uses existing data
• Reconstruct follow up period in the past

Question 10

Strengths and limitations of Retrospective studies

Answer 10

strength:
- less time consuming compared with prospective cohort studies
- less expensive
Limitations:
- The exisiting datas quality
- May not know about all relevant factors
- Bias

Question 11

Considerations of cohort studies

Answer 11

The healthy co-worker effect: when studies are derived only from a population of adult workers, this cannot be generalised to the population at larger