Which prevalence measure is highly subject to recall bias?

• A. Period prevalence
• B. Cumulative/Lifetime prevalence
• C. Point prevalence
• D. Incidence rate

Answer: (B)

Recalling past health events over a lifetime is where memory tends to fail or be inaccurate. Lifetime (cumulative) prevalence asks people to report whether they have ever had the condition at any point in their life, which requires retrieving information from many years or decades ago. This long recall period makes it highly susceptible to forgetting, misremembering, or misreporting, leading to biased estimates.

In contrast, point prevalence is about current status, and period prevalence covers a defined, typically shorter window, so the memory load is much smaller. Incidence rate focuses on new cases and, when data are collected prospectively or with precise onset timing, is less affected by memory errors. Because lifetime prevalence hinges on a long-span recall, it is the most prone to recall bias.