In epidemiological research, temporal sequence is typically established through the design of the study:
1. Cohort Studies: These studies follow a group of individuals over time to see who develops the outcome of interest. Because the exposure status is determined before the outcome occurs, cohort studies are ideal for establishing temporal sequence.
2. Case-Control Studies: These studies compare individuals with the outcome (cases) to those without (controls). Researchers look back in time to determine exposure status. While more challenging, temporal sequence can still be inferred if the exposure clearly occurred before the outcome.
3. Randomized Controlled Trials (RCTs): In RCTs, participants are randomly assigned to receive the exposure or not. This randomization ensures that the exposure precedes the outcome, thereby establishing temporal sequence.
