Cumulative or lifetime prevalence refers to:

• A. Point prevalence at a single time
• B. Prevalence of a disease during the lifetime of an individual
• C. Period prevalence over a fixed interval
• D. Incidence rate in a cohort

Answer: (B)

Lifetime (cumulative) prevalence measures the proportion of people in a population who have experienced the disease at any point up to the time of assessment. It answers the question: have you ever had this condition in your life? This differs from point prevalence, which counts only those who have the disease at a single moment, and from period prevalence, which covers everyone who had the disease during a defined time interval (not the entire life). It’s also distinct from incidence, which looks at new cases that develop over time in a population. Lifetime prevalence is often estimated by asking about ever having the condition, though recall bias can influence accuracy.