Data from a prospective cohort study examining the association between type of w
ID: 59928 • Letter: D
Question
Data from a prospective cohort study examining the association between type of work schedule and the risk of prostate cancer in men. Incidence of prostate cancer in 14,052 male workers according to type of work schedule What is the incidence density of prostate cancer in all participants in the study?
Table 1 below describes data from a prospective cohort study examining the association between type of work schedule and the risk of prostate cancer in men.
Table 1: Incidence of prostate cancer in 14,052 male workers according to type of work schedule
Work schedule
Daytime
Fixed night
Rotating shift
No. of subjects with no diagnosis of prostate cancer at the time of enrollment in the study
11,269
982
1,801
No. of person-years of follow-up
89,179
8,272
14,523
No. of new prostate cancer cases
21
3
7
Express your answers as per 10,000 person-years of follow-up where appropriate.
A. What is the incidence density of prostate cancer in all participants in the study? (2 points)
Work schedule
Daytime
Fixed night
Rotating shift
No. of subjects with no diagnosis of prostate cancer at the time of enrollment in the study
11,269
982
1,801
No. of person-years of follow-up
89,179
8,272
14,523
No. of new prostate cancer cases
21
3
7
Explanation / Answer
Incident Rate = No of new cases / Person at risk at scheduled time
person at risk = person with no cancer at the beginning + No of persons-year x 1
Incident rate of prostrate cancer for Day time workers = 21/ (11269+10000)/2 x 1=0.0019 or 0.002
Incident rate of prostrate cancer for fixed night workers = 3 / (982 + 929) / 2 x 1 = 0.003
Incident rate of prostrate cancer for rotating shift workers = 7 / ( 1801 + 1631) / 2 x 1 =0.004
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