Preventive Medicine: Epidemiology 5

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Questions and Answers

What is the primary purpose of research design?

To develop a list of possible candidates for disease causes

To make predictions from hypotheses

To collect and arrange data for analysis (correct)

To generate hypotheses for disease causes

What type of research is concerned with obtaining the frequency of a disease in a certain place at a certain time?

Qualitative research

Descriptive research (correct)

Hypothesis generation

Hypothesis testing

What is the outcome of a research question that asks 'What caused this disease?'

A hypothesis testing result

A list of possible candidates for the causes of the disease (correct)

A fair, unbiased comparison between groups

A descriptive answer

What is the purpose of hypothesis generation?

To develop a list of possible candidates for disease causes Signup and view all the answers

What is the outcome of a hypothesis testing result that does not support the hypothesis?

The hypothesis is discarded Signup and view all the answers

What is the basic function of most epidemiologic research designs?

To describe the pattern of health problems accurately Signup and view all the answers

What is the limitation of research designs?

Each design has its advantages and disadvantages Signup and view all the answers

What is the importance of data quality in research?

No research is better than the quality of the data obtained Signup and view all the answers

What is a major disadvantage of cross-sectional surveys?

They are biased towards longer-lasting and more indolent cases of diseases Signup and view all the answers

What is the primary advantage of mailed surveys?

They are relatively inexpensive Signup and view all the answers

What can repeated cross-sectional surveys be used to determine?

Changes in risk factors and disease frequency in populations over time Signup and view all the answers

What is healthy participant bias?

A bias towards participants who are more concerned about their health Signup and view all the answers

What can be inferred from a high IgG titer without an IgM titer of antibody to a particular infectious agent?

The study participant has been infected in the distant past Signup and view all the answers

What is the primary purpose of collecting acute and convalescent sera in infectious disease epidemiology?

To provide evidence about when and in whom an infection has occurred Signup and view all the answers

What is a limitation of cross-sectional surveys in determining the temporal relationship of a presumed cause and effect?

Data on exposure to risk factors and the presence or absence of disease are collected simultaneously Signup and view all the answers

What is an advantage of cross-sectional surveys?

They are useful for determining the prevalence of risk factors and the frequency of prevalent cases of certain diseases Signup and view all the answers

What is the purpose of collecting two serum samples separated by a short interval in infectious disease epidemiology?

To prove a recent acute infection Signup and view all the answers

What is the primary function of a good epidemiologic research design?

To allow a comparison of a variable between two or more groups Signup and view all the answers

What is a disadvantage of cross-sectional surveys in infectious disease epidemiology?

They are biased towards longer-lasting and more indolent cases of diseases Signup and view all the answers

Which type of research design is usually the best for testing hypotheses?

Randomized clinical trial Signup and view all the answers

What is the main difference between observational and experimental study designs?

The level of control the investigator has over the assignment of participants Signup and view all the answers

What is the purpose of qualitative research?

To provide rich, narrative information Signup and view all the answers

What is a characteristic of descriptive observational studies?

No hypotheses are specified in advance Signup and view all the answers

What is the main limitation of telephone surveys or e-mail questionnaires?

They have many nonresponders and refusals Signup and view all the answers

What is the purpose of analytic observational studies?

To measure differences between groups Signup and view all the answers

What is an advantage of qualitative research?

It provides rich, narrative information Signup and view all the answers

What is the purpose of a cross-sectional survey?

To survey a population at a single point in time Signup and view all the answers

What is a characteristic of experimental study designs?

The investigator has more control over the assignment of participants Signup and view all the answers

What is the unit of analysis in ecological studies?

Populations Signup and view all the answers

What can cross-sectional ecological studies be used for?

Suggesting hypotheses Signup and view all the answers

What is the weakness in cross-sectional ecological surveys?

Ecological fallacy Signup and view all the answers

What was found to be associated with lower rates of dental caries in children?

High levels of natural fluoridation Signup and view all the answers

What is the purpose of longitudinal ecological studies?

To determine the impact of changes in society on disease rates Signup and view all the answers

What was the result of introducing the polio vaccine in the U.S. population?

A precipitous decrease in the rate of paralytic poliomyelitis Signup and view all the answers

What is a limitation of longitudinal ecological studies?

Confounders can distort conclusions Signup and view all the answers

What is an example of a causal association suggested by longitudinal ecological studies?

Smoking and lung cancer Signup and view all the answers

In a case-control study, what is the primary factor in selecting the case and control groups?

Defined outcome, such as having a disease of interest Signup and view all the answers

What can be estimated from a case-control study?

The relative risk of the outcome Signup and view all the answers

Why are case-control studies often preferred when studying rare diseases?

They can be performed quickly and inexpensively Signup and view all the answers

What is the main difference between cohort studies and case-control studies?

Cohort studies are defined on the basis of exposure and case-control studies are defined on the basis of outcome status. Signup and view all the answers

What is the primary advantage of prospective cohort studies?

They allow for the control and standardization of data collection. Signup and view all the answers

What is the term used to describe the time relationships in a case-control study?

Simultaneous Signup and view all the answers

Why is it important to select all cases with the disease of interest in a given geographic area and time period?

To reduce bias in case selection Signup and view all the answers

What is a disadvantage of cohort studies?

They have high costs and require a long wait until results are obtained. Signup and view all the answers

What is the primary difference between a case-control study and a cross-sectional study?

The method of assembling participants Signup and view all the answers

What is the purpose of a retrospective cohort study?

To define a risk group and follow group members to see what outcomes have occurred. Signup and view all the answers

What is the term used to describe the measure of the strength of the association between the risk factor and the outcome in a case-control study?

Odds ratio Signup and view all the answers

What is an advantage of retrospective cohort studies?

They are less expensive than prospective cohort studies. Signup and view all the answers

Why are prospective cohort studies useful?

They can study multiple disease outcomes, including those not anticipated at the beginning of the study. Signup and view all the answers

What is a limitation of retrospective cohort studies?

They lack the ability to monitor and control data collection. Signup and view all the answers

What is a characteristic of prospective cohort studies?

They collect baseline data on participants and follow them for a period of time. Signup and view all the answers

What is an advantage of cohort studies?

They can study multiple disease outcomes, including those not anticipated at the beginning of the study. Signup and view all the answers

What is the main difference between a randomized controlled field trial (RCFT) and a randomized controlled clinical trial (RCCT)?

The type of intervention Signup and view all the answers

What is a disadvantage of randomized controlled field trials (RCFTs) and randomized controlled clinical trials (RCCTs)?

Results may take a long time to obtain Signup and view all the answers

What is the purpose of meta-analysis in clinical research?

To summarize the information obtained in many single studies on one topic Signup and view all the answers

What is the purpose of decision analysis in clinical research?

To show how data can inform clinical or policy decisions Signup and view all the answers

What is the purpose of cost-effectiveness analysis in clinical research?

To compare the costs and outcomes of different interventions Signup and view all the answers

What is the limitation of randomized controlled field trials (RCFTs) and randomized controlled clinical trials (RCCTs) in terms of external validity?

It may be unclear which population is actually represented by the remaining people in the trial Signup and view all the answers

What is the primary use of summary techniques in clinical preventive services?

To develop recommendations for clinical preventive services Signup and view all the answers

What is an example of a randomized controlled field trial (RCFT)?

A trial of a vaccine to prevent paralytic poliomyelitis Signup and view all the answers

What is another term for a randomized controlled field trial (RCFT)?

Community-based randomized controlled trial Signup and view all the answers

What is the purpose of postapproval surveillance in drug approvals?

To identify side effects not seen in earlier studies Signup and view all the answers

What is the term used to describe the process of looking for associations in large datasets?

Data dredging Signup and view all the answers

What is the danger of data dredging in research?

It can lead to false positive findings Signup and view all the answers

What is the purpose of a correlational study?

To develop hypotheses Signup and view all the answers

Why is it important to keep in mind the limitations of correlational studies?

Because they are limited in their ability to establish causality Signup and view all the answers

What is an example of a well-known instance of data dredging?

The association between coffee consumption and pancreatic cancer Signup and view all the answers

What is the problem that arises when looking for associations in a large dataset?

Data dredging Signup and view all the answers

Study Notes

Functions of Research Design

Research is the process of answering a question that can be answered by collecting and analyzing data
Descriptive research involves answering questions like "What is the frequency of a disease in a certain place at a certain time?"
Research designs are rules that govern the process of collecting and arranging data for analysis
Research designs can be used to generate hypotheses, test hypotheses, or both

Types of Research Design

Observational designs:
- Qualitative studies: involve anthropologic techniques like ethnographic observation, open-ended interviews, focus groups, and key informant interviews
- Cross-sectional surveys: study a population at a single point in time to determine the prevalence of risk factors and disease frequency
- Cross-sectional ecological studies: relate the frequency of characteristics and outcomes of interest in a geographic area
- Longitudinal ecological studies: measure trends in disease rates over time in a defined population
Experimental designs:
- Randomized clinical trials or randomized field trials: used to test hypotheses, with investigators controlling the assignment of participants to treatment and control groups

Observational Designs for Generating Hypotheses

Qualitative studies:
- Investigate clinical issues using anthropologic techniques
- Identify patterns in data in a structured and sometimes quantitative form
Cross-sectional surveys:
- Quick and easy to perform
- Useful for determining the prevalence of risk factors and disease frequency
- Limited by difficulties in determining the temporal relationship between exposure and disease
Cross-sectional ecological studies:
- Relate the frequency of characteristics and outcomes of interest in a geographic area
- Suggest hypotheses, but cannot draw causal conclusions
Longitudinal ecological studies:
- Measure trends in disease rates over time in a defined population
- Useful for determining the impact of public health interventions

Observational Designs for Generating or Testing Hypotheses

Cohort studies:
- Assemble a clearly identified group of people to be studied
- Assess participants to determine whether they develop diseases of interest
- Can be prospective (assemble groups in the present and follow up over time) or retrospective (use historical data to define a risk group and follow up to the present)
Case-control studies:
- Select a case group and a control group based on a defined outcome
- Compare the groups in terms of their frequency of past exposure to possible risk factors
- Can estimate the relative risk of the outcome (odds ratio), but not the absolute risk

Randomized Controlled Field Trials (RCFTs)

RCFTs are similar to RCCTs, but the intervention is preventive rather than therapeutic and conducted in the community.
Participants are randomly allocated to receive the preventive measure (e.g., vaccine, oral drug) or a placebo (e.g., injection of sterile saline, inert pill).
Examples of RCFTs include trials of vaccines to prevent paralytic poliomyelitis and aspirin to reduce cardiovascular disease.

Advantages and Disadvantages of RCFTs and RCCTs

Results may take a long time to obtain, unless the effect of the treatment or preventive measure occurs quickly.
External validity may be limited, making it unclear which population is represented by the remaining participants in the trial.

Techniques for Data Summary, Cost-Effectiveness Analysis, and Postapproval Surveillance

Meta-analysis is used to summarize information obtained in many single studies on one topic.
Decision analysis and cost-effectiveness analysis are used to summarize data and inform clinical or policy decisions.
These techniques are used to develop recommendations for clinical preventive services and community preventive services.
The U.S. Preventive Services Task Force and the U.S. Community Services Task Force use a hierarchy of evidence, with RCTs at the apex.

Postapproval Surveillance

Longer-term postapproval surveillance (Phase 4 clinical testing) is increasingly important, allowing for a larger study sample and longer observation time.
This permits the detection of side effects not seen in earlier studies, as seen in the removal of cyclooxygenase-2 inhibitor medications from the market.

Research Issues in Epidemiology

Dangers of Data Dredging

Looking for messages in data carries the potential danger of finding those that do not really exist.
"Data dredging" can lead to finding associations that do not represent true relationships.
Hypothesis development and testing should be based on different data sets.
Correlational studies are useful for developing hypotheses, not for testing them.
A celebrated example of the problem of data dredging is the reported association between coffee consumption and pancreatic cancer, which was later found to be unfounded.

The Problem of Multiple Hypotheses

With multiple hypotheses, the greater the number of hypotheses tested, the more likely that at least one of them will be found "statistically significant" by chance alone.
One possible way to handle this problem is to lower the p-value required before rejecting the null hypothesis.

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Description

Research is the process of answering a question that can be answered by appropriately collected data. This quiz explores the different aspects of research design, including descriptive research.