What is the incidence rate (absolute risk) of endometrial cancer among women who used oral
contraceptives in person-years? If the study was carried out for five years.
a) 630 / (680 x 5)
b) 75 / (320 x 5)
c) 50 / (630 x 5)
d) 75 / (320 + 5)
e) 245 / (320 x 5
Key: True: e 245 / (320 x 5)
In a prospective study of the relationship between oral contraceptive use and the subsequent
risk of developing endometrial cancer, a cohort of 1000 women were followed for 5 years. The
results were as follows:
Present Absent
A 245
B 75
C 50
D 630
A + C = 295 B + D = 705 n = 1000
What is the relative risk in this study?
a) [75 / (245 + 75)] / [50 / (50 + 630)]
b) [75 / (245 + 75)] / [630 / (50 + 630)]
c) [50 / (245 + 50)] / [630 / (75 + 630)]
d) [245 / (245 + 75)] / [50 / (50 + 630)]
e) Insufficient data
Key: True: d [245 / (245 + 75)] / [50 / (50 + 630)]