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Question: personyears at risk and incidence density personyears at risk sum...

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Person-Years at Risk and Incidence Density Person-Years at Risk sum of the amount of time a participant is at risk for the outcome in a study. (# persons x at risk for 1 year + # persons x at risk for 2 years + # persons x at risk for 3 years, etc.) Incidence Density (IDL- new cases of disease or mortality in persons at risk/person-time at risk. Incidence Density in Not Exposed (IDE) Person-time at risk Incidence Density in Exposed (IDr Person-time at risk Incidence Density Ratio (IDR -also called Relative Risk) ID/ID Compute the IDR and RR (6 points) This is an 8-year cohort study to determine the risk of smoking on developing throat cancer Some of the cohort is a past or current smoker. Others are never smokers. None has throat cancer at the beginning of the study; some develop it during the study. Compute the person-years at risk, incidence density for the exposed and unexposed groups, and the incidence density ratio. Then, interpret the findings. Steps. 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 cant be counted. Add each persons 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) (ID) & compute the incidence density for TC risk in never smokers (not exposed) (IDNE) The compute the Incidence Density Ratio (also call RR), divide the IDi by the IDsE. This value is interpreted the same as the Relative Risk.
Years Years in the Study at Risk of Developing Throat Cancer Person Smoker 1 Yes at risk at risk TC No at risk at risk at risk at risk at risk at risk at risk at risk8 No Yes Yes No No longer at risk of throat cancer TC TC TC TC H No Yes TC TC Yes Total P-Y at Risk of Throat Cancer 5. Correct table (I point) 6. Sum the Person-Years of Exposure for each exposure group? (1 point) Former/Current Smoker(1/2 point) Never Smoker (1/2 point) 7. How many of the exposed & not exposed participants developed throat cancer (1 point)? Former/Current Smoker (1/2 point) Never Smoker (1/2 point) 8. What is the Incidence Density for the exposed (IDe) and non-exposed (DA) groups? (1 point) Former/Current Smoker(1/2 point): Never Smoker (1/2 point): 2 9. 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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