Chapter 7- Study Questions PDF

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Chapter 7- Study Questions and Exercises

1. Define in your own words the following terms: a. Cohort- A group of individuals who share a common characteristic and are followed over a period of time. b. Cohort Effect- the influence of long-term secular trends in a particular cohort c. Population- based cohort- A cohort study that includes an entire population or a sample of the population. d. Exposure-based cohort- Studies that permit investigations of uncommon exposures. e. Comparison groups in cohort studies- Groups of exposed or unexposed populations. f. Prospective cohort study- A study designed to collect data on exposures. These studies are characterized by the determination of present exposure levels and follow-up in the future for occurrence of disease. g. Retrospective cohort study- A study that uses historical data to determine exposure levels from the past. h. Ambispective cohort study- Also known as a historical study; this study uses both features from retrospective and prospective cohort studies.

2. What are secular trends and cohort effects? Explain the relationship between these two terms. Secular trends are gradual changes in diseases frequency over long periods of time. Cohort effects are the consequence long-term secular trends in exposure within a specific cohort. Secular trends are periodic investigations of a disease that are due to uncommon

exposures, where cohort studies deal with fluctuations of diseases that occur due to specific exposures (Friis & Sellers, 2014). 3. Explain what is meant by the term relative risk and explain how it is used in cohort studies. Relative risk is the ratio of disease or death among the exposed to the risk among the unexposed. Risk is estimated in epidemiologic studies only by the cumulative incidence. In a cohort study, the association between exposure and disease equals the relative risk.

Relative risk=

Incidence rate∈the exposed Incidence rate∈the unexposed (Friis& Sellers, 2014, p. 347).

5. A cohort study was conducted to study the association of coffee drinking and anxiety in a population-based sample of adults. Among 10,000 coffee drinkers, 500 developed anxiety. Among 20,000 non coffee drinkers, 200 cases of anxiety were observed. What is the relative risk of anxiety associated with coffee use? Relative risk=

Incidence rate∈the exposed Incidence rate∈the unexposed

500 /10,000 0.05 =5 = 200 /20,000 0.01

6. How is a case-control study different from a retrospective cohort study? List the key criteria that, in general, would influence you to select one approach over the other. Case-control studies are studies that compare individuals who have a disease with individuals who do not have the disease in order to examine differences in exposures or risk factors for disease (Friis & Sellers, 2014, p. 739). A retrospective cohort study uses historical data to determine exposure level at some time in the past; subsequently, followup measurements of occurrence(s) of disease between baseline and the present are taken

(Friis & Sellers, 2014, p. 753). The criteria that would influence me to select one approach over the other would be, retrospective cohort studies compile significant amounts of data within a short period of time. While, case-control studies determine the subject matter based on the occurrence of the disease. Retrospective cohort studies also use larger sample sizes than case-control cohorts, whereas a case-control study involves identified cases and controls only. Another reason why retrospective cohort studies have an advantage over case-control studies is, the amount of exposure data collected can be quite extensive and can be available to the investigator at minimal cost (Friis & Sellers, 2014, pp. 343-344).

Reference Friis, R. H., & Sellers, T. (2014). Epidemiology for Public Health Practice: (5th ed.). Jones & Bartlett Learning...