Cumulative Incidence Formula Calculator
Determines the probability of developing a disease or studied outcome during the specified time period.
Refer to the text below the tool for more information about the CI and its limitations.
Cumulative incidence, also known as incidence proportion is an epidemiology measure that describes the number of new disease onsets per number of people in the population at risk. This indicator can be measured in cohorts (closed populations only) and requires follow-up of individuals.
Cumulative Incidence = No. of new cases of disease or injury / Size of population at risk x 100
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Cumulative Incidence Explained
Cumulative incidence, also known as incidence proportion is an epidemiology measure that describes the number of new disease onsets per number of people in the population at risk during a specified period of time. This indicator can be measured in cohorts (closed populations only) and requires follow-up of individuals.
CI includes only new cases of disease in the numerator. The denominator is the number of persons in the population at the start of the observation period.
Cumulative Incidence = No. of new cases of disease or injury / Size of population at risk x 100
In contrast to prevalence, incidence is a measure of the occurrence of new cases of disease (or some other studied outcome) during a specified period of time. When reporting incidence, it is important to specify the reported time because, for example, a 5% risk has a different meaning if it is probable in the next 12 months versus the next 5 years.
Whilst the CI may be an easy to understand and facile to use indicator, there are several limitations to it. CI does not distinguish when a disease or other studied outcome occurs during the time period, in some studies being of interest if outcome occurs within several months or years.
CI does not account for competing risks which may result into death of some subjects before observation period ends, meaning it cannot be discerned whether they would have or not developed the outcome of interest during the period, had they not died.
CI requires follow-up of all subjects which, in large scale studies, may be difficult to achieve, with some subjects being “lost to follow-up”.
References
Centers for Disease Control and Prevention: Principles of Epidemiology in Public Health Practice, Third Edition – An Introduction to Applied Epidemiology and Biostatistics
Specialty: Epidemiology
Article By: Denise Nedea
Published On: October 26, 2020 · 12:00 AM
Last Checked: October 26, 2020
Next Review: October 26, 2025