5. Incidence proportion (cumulative incidence) versus Incidence rate

Cumulative incidence and incidence rate are both useful, depending on the circumstance. The table below summarizes their appropriate use and their strengths and limitations.

 

Incidence proportion

Incidence Rate

Strengths
  • Easily calculated and understood since it measures risk
  • Takes into account losses to follow-up and when disease occurs

Limitations
  • Does not take into account losses to follow-up or when disease occurs
  • Need individual follow-up, which is costly and time-consuming
  • Interpretation is not intuitive

Appropriate Use
  • Fixed populations with short follow-up, or no losses to follow-up
  • Dynamic populations
  • Fixed populations with long follow-up times, or substantial loss to follow-up