# 401076 Introduction to Epidemiology Assignment 2 Answer

The University of Western Sydney

School of Science and Health

Introduction to Epidemiology (401076)

ASSIGNMENT 2

Question 1:

Liu S, Manson EJ, Stampfer MJ, Hu FB et al. A prospective study of whole-grain intake and risk of type II diabetes Mellitus in US Women. American Journal of Public Health, 2000; 90:9.   The paper is located in the assignment 2 folder in vUWS

(a) What study design does this study employ and what is the exposure and what is the outcome ? [2 mark]

(b) What justification do the authors give for conducting this study? No more than 100 words!! [4 marks]

(c) What proportion of women had history of diabetes in the family? Was it different by the quintile of whole grain intake and why it is important to show this distribution? [4 marks]

(d) What was the crude (the whole population) cumulative incidence per 1000 people and the incidence rate of diabetes per 1000 person-years during the 10 years follow -up. In your word translate the incidence rate to number of new cases that will be identified for 1000 women who were followed for 1 year and for every 1000 women who were followed for 10 years. [4 marks]

(e) Calculate the unadjusted incidence rate of diabetes due to exposure to whole grain in the first quintile (lowest level of whole gain consumption) and of the fifth quintile (highest level of consumption of whole grain. Based on this calculation determine whether there is an associated between high consumption of whole gain relative to low consumption on diabetes development and explain in your own words this association?  [4 marks]

(f) In the same table 2 the authors present age and energy-adjusted rate-ratio of the 5th quintile compared to the lowest. Did it change compared to the crude rate ratio, by how much?  What does this tell you? [4 marks]

(g) The nurses’ cohort study included 121, 700 female registered nurses aged 30 to 55 years. However, the final population in this study was much lower, 755,521 can you explain why? Do you think the smaller sample size was enough? [4 marks]

(h) What possible measurement errors could have introduced in the study and could it bias the estimate for the association between whole grain and diabetes? Have the authors try to re-assure that it shouldn’t affect the results? [4 marks]

(i) How the authors tried to deal with “reverse-causation bias” - that mean that nurses had changed the diet due to sub-clinical symptoms so that their consumption of whole grain was the resuts of the disease and not versa? [ 4 Marks

Question 2:

(20

The relationship between use of Aspirin and prostate cancer explored in a study involving 375 vases and 407 controls. In this study 198 cases and 174 of controls had confirm that they have never used Aspirin at any point.

1. Build the 2X2 table consist only with data that will help you to estimate the association between Aspirin and Prostate cancer [4 points]
2. Calculate the odds ratio of prostate cancer comparing ‘never users’ versus ever users’ and provide a one sentence interpretation of the results [4 points].
3. Calculate the attributable fraction due to “not being exposed to aspirin” and prostate cancer and explain in one or two sentences the meaning of your findings  [4 points]
4. Calculated the population attributable risk of not being exposed to asprin on prostate cancer and explain in words the meaning of such finding [4 points]
5. What do you think about the classification of aspirin intake in this way could this invites error? (no more than 3-4 sentences [4 points]

Question 3

A study examined the association between maternal use of hormones during pregnancy and increased risk of childhood cancer. It was observed that mothers who used hormones during their pregnancies were more likely to have had a history of medically complicated pregnancies.  Further, and independent of hormone use, a history of medically complicated pregnancies may be associated with a subsequent increased risk of several conditions in the children, including cancer.

If so, what source of errors could affect the results in this study?  [4 points]

Question 4

An advertisement in a medical journal stated that “2000 subjects with soar throats were treated with our new medicine and within 4 days, 94% were asymptomatic” The advertisement claims that the medicine was effective. Do you think this claim is correct? If yes why, if not why (no more than 60 words [4 points]