PUBH 8520:
Advanced Epidemiology Methods
Week 2
Assignment: Measures of Occurrence and Association
NOTE: For this
assignment it is important that you show your work. Problems where work is not
shown will not receive full credit, even if the answer is correct. Please see
the Week 2 Assignment Rubric for more details about the grading criteria for
this assignment.
Incidence Density
(25 points)
A hypothetical
cohort study was conducted to look at survival after being diagnosed with
breast cancer. Ten participants were followed for 2 years, resulting in the
following table:
Follow-up Time
(Months) Event
2 Censored
6 Death
8 Death
14 Censored
15 Death
19 Death
21 Censored
24 Followed until end of study period
24 Followed until end of study period
24 Followed until end of study period
1) What is the cumulative survival
probability at the end of the follow-up period? (8 points)
2) Using the same data, calculate the
overall death rate per 100 person-years. (3 points)
3) Calculate the rates separately for
each of the 2 years of follow-up. (9 points)
4) Based on the information above, is
it appropriate to report an overall 2-year death rate for this study? Why or
why not? (5 points)
Attributable Risk
(20 points)
A hypothetical
cohort study looked at the association between family history and the risk of
developing Parkinson’s disease. The results were as follows:
Parkinson’s Disease No Parkinson’s Disease Totals Incidence
of Parkinson’s
Family History 50 150 200 250
per 1,000
No Family History 50 750 800 62.5
per 1,000
5) Calculate the attributable risk for
Parkinson’s disease due to family history. Interpret the calculation in words.
(5 points)
6) Assume the prevalence of family
history in the general population is 10%. Calculate the population attributable
risk and interpret it in words. (7 points)
7) Now assume the prevalence of family
history in the general population is 25%. What effect does this change have on
the estimate of the population attributable risk? Discuss the relationship
between the population prevalence of exposure and the population attributable
risk. Why is it important to understand this relationship as a public health
professional? (8 points)
