Reference no: EM132553151

401076 Introduction to Epidemiology Assignment - Western Sydney University, Australia

Question 1: Read the following paper, and answer the questions below: Sundquist, K. Qvist, J. Johansson, S. Sundquist, J. "The long-term effect of physical activity on incidence of coronary heart disease: a 12-year follow-up study"

(a) What study design does this study employ, what is the exposure and what is the outcomes?

(b) What justifications do the authors give for conducting this study?

(c) What was the proportion of those who (i) do not do any physical activity (ii) engaged in twice a week vigorous physical activity? (You are not required to report 95% confidence intervals).

(d) What is the crude incidence rate of CHD in this sample what is the incidence rate in inactive men and inactive women?

(e) Calculate the relative risk of being non-active versus being "highly active" (i.e., vigorous physical activity at least twice a week) in men and in women and how would you interpret the relative risk in men and in women.

(f) Looking at the sex and age adjusted HR in Table 3 (the HR stands for Hazard Ratio which is similar to rate-rato) (i) how would you describe the association between physical activity and CHD.

(g) The authors removed from the analysis any person who self-rated their health as "bad" or "anywhere between good and bad" why? (no more than 60 words).

(h) What possible bias could have changed the estimate for the association between physical activity and CHD - at least one, and explain why.

(i) Do you think there is a risk of confounding bias in this research? Any answer yes or no must be justified.

Question 2: Tasmanian researchers conducted a case -control study to investigate the effect of dietary fat intake on skin cancer. They hypothesised that people whose dietary fat intake is low will be more susceptible to skin cancer. The study compared 500 cases of melanoma with 500 controls who were randomly selected from the state's electoral roll. The researchers categorised the dietary fat intake into three categories High, Moderate and Low. They found that among skin cancer patients 150 were classified at the low and 80 at the high dietary fat intake whereas among control 130 were at the low and 100 were at the high.

a) Build a table to summarise the data above which will help you estimate the association between dietary fat intake and Skin cancer, pay attention to headings of columns and rows.

b) Calculate the appropriate measure of relative risk (RR) of having melanoma between those consuming low fat intake versus high fat intake; calculate the appropriated measure of RR of having melanoma between those consuming medium to high fat intake and explain in words the meaning of what you found.

c) Calculate the percent attributable risk due to exposure to low-dietary fat intake on Melanoma and explain in one or two sentences the meaning of your findings.

d) Calculated the population attributable risk of low-fat intake on melanoma and explain in words the meaning of such finding.

e) What do you think about the conclusions of the PAR regarding exposure to low fat diet to reduce melanoma? (no more than 3-4 sentences).

Question 3: A study aims to determine the incidence of type 2 diabetes. A cohort of 200 people age 65 years or older who were initially disease -free participated in the study. One hundred and fifty people were examined at the end of 3 years. Fifty other participants from the initial cohort could not be examined, including 11 people who had died. Does this loss of participants represent a source of bias? Justify your answer.

Question 4: A telephone survey is being administered by several interviewers in order to collect data regarding the outcome in a randomised controlled trial. Identify the key issues the researchers should have considered in order to minimise measurement error of the outcome. Discuss the impact these issues may have on the study.