24. Experimental (interventional) epidemiological studies

Clinical trials vs field trials
- Clinical trials
  - Are performed on patients
  - Involve treatments
  - Determine secondary and tertiary preventative measures
- Field trials
  - Are performed on healthy people
  - Involve prophylactic measures
  - Determine primary preventative measures
Randomized control trials (RCT)
- Gold standard of clinical trials
- Steps
  - People from a sample population are randomly allocated into an intervention group and a control group
  - The intervention group is given the drug/therapy/etc.
  - The control group is given a placebo/the current gold standard in therapy/nothing
  - After a period of time the incidence of a specific disease between the two groups is compared
- Blinding
  - No blinding – the researchers and the study participants know which group they belong to
  - Single-blinded – only the researchers know which group the study participants belong to
  - Double-blinded – neither the researchers nor the study participants know who is in the control and who is in the interventional group
- Examples
  - 2 studies tried giving beta-carotene to smokers to see if cancer risk reduced – but the cancer risk actually increased
Crossover trial
- Similar to RCT, but the people in the control and intervention group switch during the trial period
- This allows the patients to serve as their own controls