Introduction to Epidemiology Assignment

Question 1: The following questions refers to the data from the paper by 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.

(a) What was the study design and what are the advantages of using this design?

(b) Compute the crude incidence rates of diabetes among women?

(c) Table 2 presents the adjusted relative risk of type II diabetes according to quintiles of Total Grain consumption (first 5 lines) relative to the 1st quintile (the lowest consumption as a reference). Calculate the unadjusted (crude, quintile -specific) incidence rate and the crude relative risk (RR) of each quintile in comparison to the first quintile. Comment in your own words whether any pattern of association can be observed from the unadjusted crude RR.

(d) In Table 2 model 2 (multivariables adjustment) of Whole Grain showed the RR of each quintile (increased consumption) relative to the lowest 1st. What is the pattern of the association?

(e) Why the authors adjusted their analysis for physical activity, smoking alcohol intake and family history. You need to back up your argument with evidence from the data presented in Table 1.

(f) What is the main possible bias in this study? Provide arguments for your answer and how it will affect the estimates.

Question 2: A case control study was conducted to investigate the relationship between history of sexual abuse during childhood and mental illness during adolescent. Sixty three male adolescents who were recently diagnosed with mental illness and 158 controls were enrolled to the study. A history of sexual abuse was identified in 9 controls. The prevalence of sexual abuse among cases was 3.9 -fold when compared to control.

a) Build a table to summarise the data above [hint; you need to calculate prevalence of child abuse in the control (as representing the health population) before correctly inserting the numbers in each cell)

b) Calculate the odds ratio of exposure to child abuse and risk of mental illness and explain in words the meaning of what you found.

c) What can possibly biases this estimate, explain how it will affect our measure of association- try to think of more than one possibility.

d) What is the attributable risk fraction (%) of exposure to sexual abuse among adolescents with mental illness and explain it in your own words.

e) Calculated the population attributable risk of child abuse on adolescents' mental illness and explain its meaning in your own words.

Question 3: In a small cohort study investigating the effect of a rare exposure ( E), the following results were found:

A- Is there an association between exposure and disease? Show the way you reached the conclusion. [4 points]

A stratified analysis by gender shows the following:

b. What is the relative risk (RR) of exposure causing disease men and what is the RR in women?

c- How do you explain this result? (No more than 60 words).

Question 4: What bias would you suspect in a survey of the prevalence of various electrocardiographic abnormalities after heart attack, conducted by examining all the patients treated for this condition in a university hospital in the city?

Question 5: 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.