Multicausality Confounding Assignment

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

Reserpine use Yes No Total

Obese 12.50 8.30 8.72 Not Obese 6.40 4.10 4.22 Total 10.47 6.14

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?

 

 

_____________________________________________________________________________________________ www.epidemiolog.net © Victor J. Schoenbach Multicausality: Confounding – Assignment – 374 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 (<90% predicted) and 33% of the truck shop workers had low FEV1 values. COPD and low FEV1 were strongly associated in each cohort. [FEV1 is forced expiratory volume in one second.]

a. In the above study, is smoking a likely confounder of the association between COPD and SO2 exposure (i.e., in smelters vs. truck shop workers)? Briefly discuss (1-3 sentences).

b. The best reason for not controlling for low FEV1 as a potential confounder is:

A. Low FEV1 is not associated with SO2 exposure according to the data.

B. Low FEV1 is not associated with COPD according to the data.

C. Low FEV1 is not an independent risk factor for COPD.

D. Low FEV1 is not associated with smoking according to the data.

3. Diagrammed below are two possible causal models involving oral contraceptive use (OC), plasma homocysteine level (HCS) and myocardial infarction (MI). Briefly discuss the implications of the two models with respect to whether HCS would need to be considered as a potential confounder of the relationship between OC and MI.

OC OC

HCS MI HCS MI

Other factors

Other factors

[arrows show hypothesized causal pathways]

 

 

_____________________________________________________________________________________________ www.epidemiolog.net © Victor J. Schoenbach Multicausality: Confounding – Assignment – 375 rev. 6/9/96, 9/6/1999, 3/30/2001

4. The following table, published in the Oxford Family Planning Association Contraceptive Study (Vessey et al.), shows characteristics of individuals at the time of recruitment in to the study. Based on the data presented in the table, discuss three potential sources of bias apparent from the characteristics of the three contraceptive groups. How would these factors be expected to influence the appearance of a causal association between oral contraceptive use and circulatory deaths if no adjustment for the factors were carried out?

Some characteristics of subjects in the three contraceptive groups at time of recruitment

Method of Contraception in use on Admission

Characteristic Oral Diaphragm IUD Percentage aged 25-29 years 56 35 35 Percentage in Social Classes I or II* 39 49 34 Percentage smoking 15 or more cig./day 17 7 12 Mean Quetelet’s Index** 2.25 2.26 2.31 Percentage*** with history of:

Hypertension 0.91 0.67 0.50 Pre-eclamptic toxaemia 12.58 16.26 16.07 Stroke 0.03 0.04 0.30 Rheumatic fever 0.76 0.66 1.04 Rheumatic heart disease 0.09 0.26 0.32 Congenital heart disease 0.12 0.31 0.16 Venous thromboembolism 0.87 4.30 7.96

* Registrar General’s classification [Social Class I is highest]

** Weight (g) / height (cm)2. *** Standardized by indirect method for age and parity. See Vessey, et al.

5. The following questions (from the 1985 EPID 168 second midterm exam) are based on data from Kantor AF, Hartge P, Hoover RN, et al. Urinary tract infection and risk of bladder cancer. Am J Epidemiol 1984;119:510-5). In that study, 2982 newly-diagnosed bladder carcinoma patients identified through the U.S. National Cancer Institute SEER (Surveillance, Epidemiology and End Results) Program during a one-year period beginning in December 1977 were interviewed. 5782 population controls from the same geographic areas covered by SEER were selected using an age- and sex-stratified random sample of the general populations, with 2:1 frequency-matching of controls to cases. Information on physician-diagnosed urinary tract infections (UTI) more than one year before interview (and many other factors) was obtained through personal interviews using structured questionnaires in respondents’ homes. The following data are from Table 1 in Kantor, Hartge, Hoover et al.:

 

 

_____________________________________________________________________________________________ www.epidemiolog.net © Victor J. Schoenbach Multicausality: Confounding – Assignment – 376 rev. 6/9/96, 9/6/1999, 3/30/2001

Table 1 Relative risks (RR) of bladder cancer associated with

history of urinary tract infection,* by number of infections;

10 geographic areas of the United States, 1978

Males Females

No. of urinary tract infections

Cases Controls RR 95%

confidence interval

Cases Controls RR 95%

confidence interval

0 1758 3642 1.0+ 398 979 1.0+ 1 or 2 309 423 1.5 (1.3-1.8) 176 296 1.2 (0.9-1.5)

3+ 146 152 2.0 (1.6-2.6) 145 206 2.1 (1.6-2.7)

* Maximum likelihood estimate of relative risk adjusted for race, age, smoking status (never smoked, ex-smoker, current smoker) from stratified analyses.

+ Reference category

a. The sex-specific relative risks for bladder cancer (BC) shown in Table 1 are adjusted for race, age, and smoking status. Which one of the following could be the relative risk of BC risk for 3+ urinary tract infections (UTI) adjusted for race, age, smoking status, and gender? [Choose one best answer]

A. 1.33

B. 1.92

C. 2.05

D. None of the above.

b. Using the data in Table 1, construct a labeled 2 by 2 table for estimating the crude (with respect to race, age, smoking status, and gender) relative risk for BC in men and women who have a history of 3+ UTI compared to men and women with no history of UTI. Your answer should show the correct formula and substitution.

c. Is gender associated with history of 3+ UTI? Support your answer with the most relevant numbers from Table 1.

d. Is gender a confounder of the association between BC risk and history of 3+ UTI? Support your answer with data from Table 1 and/or your answers to the two preceding questions._

StudyAcer
Calculate your paper price
Pages (550 words)
Approximate price: -
StudyAcer

Quality Researched Papers

We always make sure that writers follow all your instructions precisely. You can choose your academic level: high school, college/university or professional, and we will assign a writer who has a respective degree.

StudyAcer

Qualified Writers

We have hired a team of professional writers experienced in academic and business writing. Most of them are native speakers and PhD holders able to take care of any assignment you need help with.

StudyAcer

Unlimited Revisions

If you think we missed something, send your order for a free revision. You have 10 days to submit the order for review after you have received the final document. You can do this yourself after logging into your personal account.

StudyAcer

Prompt Delivery

All papers are always delivered on time. In case we need more time to master your paper, we may contact you regarding the deadline extension. We will always strive to deliver on time.

StudyAcer

Original & Confidential

We use several writing tools checks to ensure that all documents you receive are free from plagiarism. Our editors carefully review all quotations in the text.

StudyAcer

24/7 Customer Support

Our support agents are available 24 hours a day 7 days a week and committed to providing you with the best customer experience. Get in touch whenever you need any assistance.

Try it now!

Calculate the price of your order

Total price:
$0.00

How it works?

Follow these simple steps to get your paper done

StudyAcer

Place your order

Fill in the order form and provide all details of your assignment.

StudyAcer

Proceed with the payment

Choose the payment system that suits you most.

StudyAcer

Receive the final file

Once your paper is ready, we will email it to you.

Academic Writing Services

If you are looking for exceptional academic writing services, then you are in the right place. Studyacer offers customised academic assignments and academic papers for students at all levels.

StudyAcer StudyAcer

Essays

Essay Writing Help

Writing an essay can be a challenge. However, we know what every student needs. And we purpose to deliver. Here at StudyAcer, we do all we can to help with academic essays and assignments. We have a dedicated team of professional essay writers.

StudyAcer StudyAcer

Assignment

Assignment Help

We understand students need satisfactory results. Our cheap assignment writing service helps and never leaves any doubt. We always strive to ensure the ultimate and best results. It is our joy to offer a cheap reliable essay writing service.

StudyAcer StudyAcer

Term paper

Term Paper Help

Have you been asking yourself, where can get a pre written research papers for sale? Worry no more, the fact that you have a term paper that is due tonight and you haven’t touched it. At Study Acer it is our responsibility to get your paper on time.

StudyAcer StudyAcer

Dissertation

Dissertation Writing Service

Several master’s students seek professional help with their thesis.Students from different parts of the world experience different challenges. Dissertations have different stages and the challenges are different too. Do not struggle in silence, order now .