Reference no: EM132649157

Question 1:

An epidemiologic study was conducted among workers at a new pesticide manufacturing plant in Kentucky. The purpose of the study was to see if routine exposure to pesticide residue increased the risk of acute respiratory infection (ARI). All 375 workers in the plant participated the study during a full year of follow-up and all were free from ARI at the start of the study.

Pesticide levels were monitored daily in two sections of the plant, one in which pesticides were stored and handled on a high volume basis and one in which non-pesticide operations took place. 254 plant workers were assigned to the high-volume pesticide location and the remaining workers were assigned to the non-pesticide location.
All workers underwent monthly health exams in which they were tested for ARI. At the conclusion of the study, 57 participants had been diagnosed with at least one ARI. 48 of these were among the workers assigned to the high volume pesticide location and 9 among the remaining workers.
a) In two sentences, is this an example of a prospective cohort study or a retrospective cohort study? How do you know?
b) Who is in the exposed population? Who is in the unexposed population?
c) Construct a 2x2 table for the results of this study. Place the results provided in the problem in the appropriate cells of the 2x2 table.
d) Calculate the cumulative incidence of ARI during the study.
e) A majority of the workers in the high-volume pesticide location are men. Data show that a higher proportion of men in Kentucky smoke compared to women. Based on this new information, do you believe that selection bias played a role in these study findings? Explain why or why not.

You should be able to adequately respond in 4-6 sentences, but feel free to write more if you wish.

Question 2:
You are working with a team in Sweden to investigate the extent to which in vitro fertilization (IVF) is associated with four adverse birth outcomes: low birth weight, congenital malformation, chromosomal abnormality, and diagnosis of cognitive disorders up to age 5. The following sources of data are available to you; each has been continuously maintained since January 1982. In Sweden, mothers and babies are identified by a unique identification number that can be used to link across data sources.

• Swedish Medical Birth Registry - includes birth certificate data on all children born in Sweden
• Records of National Board of Health and Welfare - includes reports from all 14 IVF clinics in Sweden regarding who underwent IVF and when they had their procedure
• Records from all 26 childhood disability centers in Sweden - includes diagnosis data on all children treated for cognitive disorders during childhood

Answer the following questions:
a) In two sentences, is this an example of a prospective cohort study or a retrospective cohort study? How do you know?
b) What is the timeframe of your study, meaning what years of data will you include? Hint: Think about when each of the outcomes is assessed.
c) Who is in the exposed population? Who is in the unexposed population?
d) Which data source(s) would you use to identify exposure status and outcome status? (Remember that there are multiple outcomes in this study)

Question 3:
You have been asked to investigate the association between exposure to low-level radiation emanating from a nearby nuclear plant and risk of mortality (death) from all causes. There is a large recreational sports facility located 0.5 miles from the nuclear plant. The sports facility has near-complete records on all its members, including names, addresses, and ages; furthermore, all members visit the facility on a regular basis, making them easy to locate and track. In an effort to avoid loss to follow-up, you select members of this sports facility as your exposed population. For your non-exposed population, you select individuals of similar age, sex, and racial/ethnic characteristics from an area at least 50 miles away from the nuclear plant. Identify and explain two types of bias are you likely to have introduced to this cohort study.

Hint: There is no single correct answer. Remember that bias is a difference that affects BOTH your exposure and outcome. You should be able to adequately describe each source of bias in 2-4 sentences, but feel free to write more if you wish.