Enter the number of patients and the duration of exposure into the calculator to determine the patient year exposure.
Disclaimer: For educational/statistical estimation only (not medical advice). For clinical studies, patient‑years are typically calculated as the sum of each participant’s exposure/follow‑up time and incidence/CIs depend on modeling assumptions (e.g., Poisson); follow your protocol/statistical analysis plan and consult a qualified biostatistician for interpretation.
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Patient Year Exposure Formula
The following formula is used to calculate the patient year exposure for a given number of patients and duration of exposure.
PYE = N * D
Note: In general, patient‑years (person‑time) are calculated as the sum of each participant’s exposure/follow‑up time. The simplified formula PYE = N × D applies only when all N patients have the same exposure duration D (no staggered entry, censoring, discontinuation, or loss to follow‑up).
Formula source: Hazra A, Gogtay N. Biostatistics Series Module 8: Assessing Risk. Indian J Dermatol. 2017;62(2):123–129.
Variables:
- PYE is the patient year exposure
- N is the number of patients
- D is the duration of exposure in years
To calculate the patient year exposure, multiply the number of patients by the duration of exposure in years when all patients have the same exposure duration. If exposure times vary, compute PYE by summing individual exposure durations across participants.
What is Patient Year Exposure?
Patient year exposure is a measure used in clinical studies to quantify the amount of exposure to a treatment or condition across a population over a period of time. It is calculated by multiplying the number of patients by the duration of exposure in years. This metric helps researchers understand the extent of exposure and is often used to assess the safety and efficacy of treatments in long-term studies.
How to Calculate Patient Year Exposure?
The following steps outline how to calculate the Patient Year Exposure.
- First, determine the number of patients (N).
- Next, determine the duration of exposure in years (D).
- Finally, calculate the patient year exposure using the formula PYE = N * D.
- After inserting the values and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Number of patients (N) = 100
Duration of exposure in years (D) = 2
