PUB 540 GCU Multicausality Confounding Cancer Obesity & Fat cells Discussion Based on the “Multicausality: Confounding – Assignment,” by Schoenbach, discus

PUB 540 GCU Multicausality Confounding Cancer Obesity & Fat cells Discussion Based on the “Multicausality: Confounding – Assignment,” by Schoenbach, discuss two significant insights you learned about confounding. Use specific examples from the assignment to support your answer. Multicausality: Confounding – Assignment
1. Some years ago several studies were published showing an association between reserpine (a drug
used to lower blood pressure) and breast cancer in women. Since obesity is associated both with
breast cancer and with hypertension (elevated blood pressure), the suspicion arose that the
association between reserpine and breast cancer could be secondary to the effect of obesity.
Assume that a cohort study had been conducted to address this question and produced the
following data:
Annual age-adjusted incidence of breast cancer per 100,000 women
by body weight and reserpine status
Obese
Not Obese
Total
Yes
12.50
6.40
10.47
Reserpine use
No
8.30
4.10
6.14
Total
8.72
4.22
Answer the following questions on the basis of the above data (ignore considerations of
statistical significance and precision). For each answer cite the most relevant figures from the
table, allowing for the possibility that one factor affects the observed relation between the other
factor and breast cancer risk.
a. Is reserpine a risk factor for breast cancer?
b. Is obesity a risk factor for breast cancer?
c. Is reserpine use associated with obesity?
d. Is the association between reserpine and breast cancer attributable to obesity?
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www.epidemiolog.net © Victor J. Schoenbach
Multicausality: Confounding – Assignment – 373
rev. 6/9/96, 9/6/1999, 3/30/2001
2. A 20-year retrospective cohort study of the incidence of chronic obstructive pulmonary disease
(COPD) was performed in two occupational cohorts with different levels of S02, copper smelters
(high SO2) and truck maintenance workers (low SO2). In 1961, when the cohort was defined,
55% of the smelter workers and 55% of the truck shop workers were smokers. The relative risk
for COPD due to smoking was 10.5 among the smelters and 3.0 among the truck shop workers.
Pulmonary function data taken in 1980 showed that 75% of the smelter workers had low FEV1
values (
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