Recall bias is a concern primarily in which type of study?

• A. Retrospective studies
• B. Prospective cohort studies
• C. Randomized controlled trials
• D. Cross-sectional studies

Answer: (A)

Recall bias happens when people’s memory of past exposures is influenced by their current health status, causing differential accuracy in reporting. This is most likely in retrospective designs because exposure information is collected after the outcome has occurred, often by asking participants to recall events from the past. Those with the disease may remember or interpret past exposures differently than those without the disease, skewing the association.

In prospective cohorts, exposure data are gathered before the outcome happens, so memory is less of a factor. In randomized trials, exposure is assigned by investigators (often with blinding), which limits differential reporting. Cross-sectional studies can involve recall of past exposures, but the design most inherently prone to recall bias is the retrospective approach where outcome status already exists when exposure is assessed.