EDAPT Global Population Health Practice Exam

The main idea is that incidence rate (incidence density) measures how fast new cases accumulate and uses person-time in the denominator, while cumulative incidence (incidence proportion) is a probability of developing the disease over a defined period and uses the number of people at risk at the start divided by that initial population. Incidence rate accounts for varying follow-up times because it sums the exact time each person is at risk, yielding a rate such as cases per person-year. Cumulative incidence, on the other hand, reflects the risk over a set time window for a baseline population, essentially the proportion who develop the disease during that period, assuming they’re all followed for the full interval (ignoring censoring details in its simplest form). So the statement that incidence rate uses person-time and cumulative incidence is risk over a specified period is the correct distinction.