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Question: compute the personyears of smoking exposure using the table below...

Question details
  • Compute the Person-Years of smoking exposure using the table below. (Hint: add the years at risk of throat cancer (TC) – see examples).
  • Once they develop TC they are no longer at risk and their years in the study can’t be counted.  
  • Add each person’s years of exposure in the right column and enter the value in the box next to “Total P-Y at Risk of Throat Cancer”.
  • Then count the P-Y at risk for the Current/Former Smokers (exposed) and the P-Y at risk for the Never-Smokers (not exposed)
  • Using the Person-Years for each exposure group as the denominator and the number of TC recorded for each exposure group; compute the Incidence Density for TC risk in current/former smokers (exposed) (IDE) & compute the incidence density for TC risk in never smokers (not exposed) (IDNE).
  • The compute the Incidence Density Ratio (also call RR), divide the IDEby the IDNE. This value is interpreted the same as the Relative Risk.

Years in the Study at Risk of Developing Throat Cancer

Years at Risk

Person

Smoker

1

2

3

4

5

6

7

8

A

Yes

at risk

at risk

TC

No longer at risk of throat cancer

    2

B

No

at risk

at risk

at risk

at risk

at risk

at risk

at risk

at risk

    8

C

No

D

Yes

TC

E

Yes

TC

F

No

G

No

TC

H

No

TC

I

Yes

TC

J

Yes

TC

Total P-Y at Risk of Throat Cancer

  1. Sum the Person-Years of Exposure for each exposure group? (1 point)

Former/Current Smoker (1/2 point)

Never Smoker(1/2 point)

  1. How many of the exposed & not exposed participants developed throat cancer (1 point)?  

Former/Current Smoker (1/2 point):                   

Never Smoker(1/2 point):                      

  1. What is the Incidence Density for the exposed (IDE) and non-exposed (IDNE) groups? (1 point)

Former/Current Smoker (1/2 point):         

Never Smoker (1/2 point):

  1. Compute the Incidence Density Ratio (IDR). Is the IDR protective or hazardous? (1 point).

10.  Using the interpretation for Relative Risk on page 120 of your text, interpret the meaning of the Incidence Density Ratio (1 pt):

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