Module 3 Epidemiological Study Designs

Consider a cohort of 2,000 people, of whom 800 are smokers and 1,200 are non-smokers. The entire cohort is observed for 20 years, and 100 participants develop lung cancer, of who 90 are smokers and 10 are not. What is the relative risk of lung cancer for smokers to non-smokers in this cohort?

13.5

A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. What was the cumulative incidence of anxiety among coffee drinkers? Calculate the relative risk using the given data assuming that coffee drinking is the exposure. The numeric value of the relative risk is....

5.0

Consider a cohort of 2,000 people, of whom 800 are smokers and 1,200 are non-smokers. The entire cohort is observed for 20 years, and 100 participants develop lung cancer, of who 90 are smokers and 10 are not. What is the incidence rate of lung cancer for non-smokers in this cohort per 1,000?

8.3 per 1,000

What sources can be used to identify controls for a case-control study?

All of the above

Smoking histories are obtained from all patients entering a hospital who have lip cancer and are compared with smoking histories of patients with cold sores who enter the same hospital. This is an example of which type of study?

Case-control

Which of the following is a method of sampling a population in which researchers identify and enroll cases of disease and a sample of the source population that gave rise to the cases?

Case-control study

A study in which children are randomly assigned to receive either a newly formulated vaccine or the currently available vaccine, and are followed to monitor for side effects and effectiveness of each vaccine, is an example of which type of study?

Clinical trial

To test the efficacy of vitamin C in preventing colds, army recruits are randomly assigned to two groups: one given 500 mg of vitamin C daily, and one given a placebo. Both groups are followed to determine the number and severity of subsequent colds. This is an example of which type of study?

Clinical trial

A cohort study of coffee drinking and anxiety was conducted at a university campus. There were a total of 30,000 freshmen who participated. 10,000 were coffee drinkers and 20,000 were not. Of the coffee drinkers, 500 developed anxiety during the 4 year follow-up period. Of the non-coffee drinkers, 200 developed anxiety during the same time period. Assume that no one in the population died or was lost during the follow-up period. What was the cumulative incidence of anxiety among coffee drinkers? Which of the following is the correct interpretation of the relative risk?

Coffee drinkers are "x" times as likely to develop anxiety as compared to non-coffee drinkers

Fifteen hundred adult men who worked for Lockheed Aircraft were initially examined in 1951 and were classified by diagnostic criteria for coronary artery disease. Every three years they have been reexamined for new cases of the disease: attack rates in different subgroups have been examined annually. This is an example of which type of study?

Cohort

The physical examination records of the incoming first-year class of 1935 at the University of Minnesota are examined in 1980 to see whether the freshmen's recorded height and weight at the time of admission to the university were related to their chance of developing coronary heart disease by 1981. This is an example of which type of study?

Cohort

Which of these study designs would be considered the most valid?

Cohort study

This study design looks at a "snapshot" of the burden of disease and exposure in a population of individuals at one point in time.

Cross-sectional studies

The Seven Countries study, which examined the relationship between lifestyle, diet, and coronary heart disease in 7 counties, is an example of which study design?

Ecologic

Which type of study evaluates an association using the population rather than the individual as the unit of analysis?

Ecological study

The high degree if validity in which type of study stems mainly from the investigator's ability to randomize subjects to either the treatment group or the comparison group and thereby control for distortions produced by confounding variables?

Experimental Study

An experimental study design is appropriate if the exposure you are studying is race.

False

Associations that are found at the group level can be used to infer that there exists an association at the individual level.

False

Only one experimental intervention can be run at the same time.

False

The individual is the unit of analysis for ecologic studies.

False

Although there are several advantages to using the general population as a comparison group, which of the following is the main disadvantage?

Healthy worker effect

The main disadvantage of using which type of controls is the difficulty in determining appropriate illnesses for inclusion?

Hospital and clinic controls

The exposed group can also be referred to as which of the following?

Index group

Which of the following are key features of cohort studies (select all that apply)

Retrospectively or prospectively the investigators identify a cohort of subjects who initially did not have the disease or outcome of interest. The groups being compared differ in their exposure status Investigators measure and compare the incidence of disease (or some outcome) among different exposure groups.

A new cholesterol treatment is being tested during a clinical trial with over 3,000 patients. The patients in the study don't know if they are receiving the new treatment or a placebo. The people testing the new treatment do know what participants are receiving. This is an example of:

Single blind study

Consider a cohort of 2,000 people, of whom 800 are smokers and 1,200 are non-smokers. The entire cohort is observed for 20 years, and 100 participants develop lung cancer, of who 90 are smokers and 10 are not. Which is the correct interpretation for relative risk?

Smokers are "x" times as likely to develop lung cancer as compared to non-smokers

Epidemiologic studies that examine the role of a suspected factor in the etiology of a disease may be observational or experimental. The most important difference between experimental and observational studies is that in experimental studies: (Choose one answer)

The investigator determines who shall be exposed to the suspected factor and who shall not

A case-control study is more efficient than a cohort study when the disease is rare.

True

Cohort studies are good for studying rare exposures but are not as efficient as case-control studies for studying rare outcomes.

True

Observational studies take advantage of the fact that people expose themselves to noxious or healthy substances through their personal habits.

True

The individual is the unit of analysis for case-control studies

True

A clinical trial...

Uses volunteers to study the efficacy an experimental drug, therapy, lifestyle change, or test against a control

The fulfillment of which concept is crucial to the validity of a case-control study?

Would criterion

A cross-sectional study is:

a study that takes place at one time and examines the prevalence of exposures and/or health outcomes

The ecological fallacy is:

bias that might occur because an association observed at the aggregate level does not necessarily represent the association that exists at an individual level

British investigators conducted a study to compare measles-mumps-rubella (MMR) vaccine history among 1,294 children with pervasive development disorder (e.g., autism and Asperger's syndrome) and 4,469 children without such disorders. (They found no association.) This is an example of which type of study?

case-control

Su et al. examined the association between breast cancer incidence and viral hepatitis among women in Taiwan. A total of 1958 patients with incident breast cancer during the period 2000-2008 were identified and age-matched to 7832 subjects without cancer. No significant association between breast cancer incidence and hepatitis C virus or hepatitis B virus was found. What type of study design was this?

case-control study

Which type of observational study examines one or more health effects/outcomes of exposure to a single agent?

cohort study

Which type of studies typically take a snapshot of a population at a single point in time and therefore usually measures the disease prevalence, exposure prevalence, or relationship between the two?

cross-sectional study

In a cross-sectional study of the association between alcohol consumption and dementia, the most appropriate effect measure to calculate is:

odds ratio

Which type of bias occurs when there is a differential level of accuracy in the information provided by compared groups?

recall bias

An odds ratio of 2.0 calculated in a cross-sectional study suggests:

the exposure is more common among individuals with the health outcome

A cohort study must have at least how many points of measurement?

two

An important weakness of cross-sectional studies is:

we usually identify a large proportion of prevalent cases