Epidemiology: Incidence and Prevalence · USMLE Step 1

In a stable population, which relationship is generally true?

  1. Prevalence < incidence
  2. Incidence = prevalence × duration
  3. Prevalence increases when incidence decreases
  4. Incidence = prevalence ÷ duration
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Correct answer: Incidence = prevalence ÷ duration

For a stable population prevalence ≈ incidence × duration. Rearranging gives incidence = prevalence ÷ duration, so this is the relationship that holds.

Difficulty: Medium Question 11 of 20

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