Incidence rate and cumulative incidence are related concepts. A rate implies time. The denominator is often expressed in person years such as 300 new kidney stones/100,000 person years. This can be conceptualized as 300 cases in 100,000 persons observed for 1 year or, equally, 30 cases in 10,000 persons observed for 10 years.

Cumulative incidence is the number of new cases within a specified time period divided by the size of the population initially at risk (e.g. 60 cases of kidney stones develop in a population of 10,000 over 2 years).

Dear Gregory, Thanks for your interest in the topic and your answer. However in your answer, you have not touched upon the term 'cumulative risk'. Please highlight the difference between cumulative rate and cumulative risk.

Sorry, not actually sure what you mean by cumulative rate and cumulative risk. In what are you interested?

Cumulative risk is cumulative proportion not taking into account the time factor.

For a rare condition, the cumulative rate is approximately equivalent to cumulative risk. An important difference is that the cumulative risk (e.g a 10-year cumulative risk is a probability (often expressed as a percentage) of developing the condition in the next 10 years). In any case, if you have 10-year cumulative rate values, you can convert them into 10-year cumulative risk values by using the formular;

10-year cumulative risk (%) = 100*(1-e^(-(10-year cumulative rate))).