Case-control

Question 1

Case-controls
General info

Answer 1

1. Start with Cases & Controls (DISEASE)
2. Assess EXPOSURE retrospectively

Question 2

Case-controls
Advantages

Answer 2

1. Rare diseases/outcomes. Diseases Long latency (Cancer)
2. More than one exposure at a time.
3. Smaller, quicker and less expensive vs Cohort

Question 3

Case-controls
Disadvantages

Answer 3

1. Not useful for rare exposures (Cohort for rare exposures)
2. Temporal relationship is unclear
3. May not provide info on prevalence of disease
4. Cannot provide direct estimate for risk
5. Bias
   Selection bias: C&C not represnt all population
   Information/Measurement: Collected information diff.
   Confoundings: other factors, misleading results.

Matching helps reduce Bias and confounding
* Individual matching (Common)
* Frequency of group matching

Question 4

Case-controls
Formula and interpretation

Answer 4

Odds Ratio (POR) ` (a/c)÷(b/d)`

• a/c odds of exposure in cases (disease)
• b/d odds of exposure in controls (non disease)

The odds of HEAVY DRINKING among those with DEPRESSION is 1.5 the odds of HEAVY DRINKING among patients without DEPRESSION

OR/RR