7.2.1 - Case-Cohort Study Design

A case-cohort study is similar to a nested case-control study in that the cases and non-cases are within a parent cohort; cases and non-cases are identified at time \(t_1\), after baseline. In a case-cohort study, the cohort members were assessed for risk factros at any time prior to \(t_1\). Non-cases are randomly selected from the parent cohort, forming a subcohort. No matching is performed.

Advantages of Case-Cohort Study:

Similar to nested case-control study design:

  • Efficient– not all members of parent cohort require diagnostic testing
  • Flexible– allows testing hypotheses not anticipated when the cohort was drawn \((t_0)\)
  • Reduces selection bias – cases and noncases sampled from same population
  • Reduced information bias – risk factor exposure can be assessed with investigator blind to case status

Other advantages, as compared to nested case-control study design:

  • The subcohort can be used to study multiple outcomes
  • Risk can be measured at any time up to \(t_1\) (e.g. elapsed time from a variable event, such as menopause, birth)
  • Subcohort can be used to calculate person-time risk

Disadvantages of Case-Cohort Study as compared to nested case-control study design:

  • Increased potential for information bias because
    • subcohort may have been established after \(t_0\)
    • exposure information collected at different times (e.g. potential for sample deterioration)

Statistical Analysis for Case-Cohort Study:

Weighted Cox proportional hazards regression model (we will look at proportional hazards regression later in this course)