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GCH 412
Homework 6 (Case-Control Studies)
Homework 7 (Cohort Studies)
1. Among older adults (those 65 or older), falls are the leading cause of injury and death.
They are also the most common cause of nonfatal injuries and hospital admissions for
trauma. Researchers were interested in the association between hip fractures from falls
and living alone. They recruited women in the Boston metropolitan area between the ages
of 65 and 85 for the study. Specifically, they recruited 236 women who had broken a hip
in a fall in the last 6 months and 414 women who did not have a broken hip. They were
then asked whether they lived alone or not. Of those with a broken hip, 125 lived alone.
Of those without a broken hip, 369 lived with a spouse, other family member or in
assisted living. Complete the 2×2 table and answer the following questions based on this
information.
a. What is the exposure and what is the outcome?
b. What type of study design is this? How do you know?
c. Calculate the odds of exposure in the disease group.
d. Calculate the odds of exposure in the non-disease group.
e. What is the proper measure of association for this study design? Calculate it and interpret
what that specific association means in words.
f. If appropriate, calculate the AR% and interpret what it means. If it is not appropriate,
explain your answer.
2. A study was conducted to assess the association between benzene exposure and
leukemia. The investigators selected 2000 workers who were occupationally exposed to
benzene and 5000 workers who had no occupational benzene exposure and followed
them all for 10 years. No one had leukemia at the beginning of the study. At the end of
the study period, there were 42 cases of leukemia among the benzene exposed workers
and 18 among the non-exposed workers. Complete the 2×2 table, labeling the exposure
and disease boxes with the proper information. Show all your work for the calculations.
a. What type of study design is this? How do you know?
b. Calculate the incidence of disease in the exposed group.
c. Calculate the incidence of disease in the unexposed group.
d. State the appropriate measure of association, calculate it, and interpret this association
in words.
e. If appropriate, calculate the AR% and interpret what it means. If it is not appropriate
to calculate the AR%, explain your answer.
f. If you calculated the AR% answer the following: How many cases of leukemia in this
study could have been prevented by protecting workers against benzene exposure?
How many cases of leukemia in the exposed group were not due to benzene
exposure?
3. Fungal meningitis can develop after a fungus spreads through the bloodstream from
somewhere else in the body, as a result of the fungus being introduced directly into the
central nervous system, or from an infected body site infection next to the central nervous
system. You may also get fungal meningitis after taking medications, including steroids
such as prednisone that weakens the immune system. Fungal meningitis is not
contagious. CDC is coordinating a multistate investigation of meningitis to determine if
those with this form of meningitis received epidural steroid injections (medication
injected into the spine). A total of 500 cases of possible meningitis were reported to the
CDC in the month of September. Of those 500 cases, 227 were fungal meningitis; the
remainder were bacterial or viral meningitis. Of the 227 cases of fungal meningitis, 152
people had received epidural steroid injections. Of those without fungal meningitis, 79
had received epidural steroid injections. Complete the 2×2 table and answer the following
questions based on this information
a. What kind of study design is this and how do you know?
b. What is the proper measure of association for this study design?
c. Calculate the measure of association and interpret what your results mean in words.
d. Can you calculate the AR% from the information provided? If so, calculate it and explain
what it means. If not, explain why it cannot be calculated.
4. Suppose that 2000 pregnant women were identified during their 1st trimester and
completed questionnaires about health behaviors, including alcohol consumption. Among
the 800 women who drank alcohol during pregnancy, 200 delivered low birth weight
(LBW) infants. Among the 1200 who did not drink alcohol during pregnancy, 150
delivered low birth weight babies. Complete the 2×2 table, labeling the exposure and
disease boxes with the proper information. Show all your work for the calculations.
a. What type of study design is this? How do you know?
b. What is the appropriate measure of association?
c. Calculate the proper measure of association. Interpret your results in words.
d. Can you calculate the AR% from the information provided? If so, calculate it and explain
what it means. If not, explain why it cannot be calculated.
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