A report states 20% of the population will develop heart disease at some point in their lifetime. This is an example of which epidemiologic measure?

• A. Incidence rate
• B. Prevalence rate
• C. Mortality rate
• D. Morbidity rate

Answer: (A)

This statement reflects the chance that a person will develop a disease over a period of time, specifically over a lifetime. That’s a measure of incidence over time, described as cumulative incidence or incidence proportion—the probability that a disease-free individual will develop the disease during the defined span, here the entire life. It’s not about how many people have the disease at a single point (prevalence), nor about deaths (mortality), nor a general disease frequency without reference to new cases (some forms of morbidity measures). Among the options, the term that best aligns with new cases arising in a population over a period is incidence rate, which captures the occurrence of new cases over time. Thus, lifetime risk aligns with cumulative incidence, which is the essence of this measure.