Epidemiological Studies

Question 1

List four applications of epidemiological studies.

Answer 1

Clarify clinical and demographic characteristics

Identify which populations are at risk

Provide clues to cause of disease

Guide in preventative measures and interventions

Question 2

From the observations gathered during the descriptive process, a _____________ is generated about the causes of observed patterns, and the factors that increase the risk for disease or injury.

Answer 2

Hypothesis

Question 3

Outline descriptive studies.

Answer 3

Describes the specific characteristics in a population of interest

What, when, where, who (from clinical Information and surveillance data)

Use accessible data

What (symptoms, lab results, etc.)

Who (demographics, e.g., age, race, gender, culture, etc.)

Where (where did illness begin, exposure occur, etc.)

When (time, trends, patterns, epidemics, etc.)

Question 4

List three forms of descriptive study.

Answer 4

Case report

Case series

Incidence study

Question 5

What two values do descriptive studies principally measure?

Answer 5

Prevalence and incidence

Question 6

What is the aim of analytical epidemiology?

Answer 6

Attempts to provide the ‘why’ and ‘how’ of such health-related events, by comparing groups of individuals

Question 7

Name three epidemiological determinants.

Answer 7

Agents

Hosts

Environments

Question 8

__________ epidemiology attempts to determine the cause of an outbreak.

Answer 8

Analytical

Question 9

Experimental analytical epidemiology is also called _____________ epidemiology.

Answer 9

Interventional

Question 10

Describe experimental epidemiology.

Answer 10

Investigator can control the exposure
Akin to laboratory experiments, except living populations are the subjects
Generally, involves random assignment to groups, following over time and monitoring
Clinical trials are the most well-known experimental design (generating data from individuals)

This type is the ultimate step in testing causal hypotheses
In an experiment, there is an interest in the consequences of some treatment on some outcome
The subjects in the study who receive the treatment of interest are called the treatment group

The subjects in the study who receive no treatment, or a different treatment, are called the comparison group or control group

Question 11

What is a randomised control trial?

Answer 11

A design with subjects randomly assigned to treatment and comparison groups

Question 12

List three advantages of randomised control trials.

Answer 12

First randomization reduces the influence of other determinants of exposure and outcomes, i.e., confounding
The ‘gold standard’ of research designs

Provides most convincing evidence of relationship between exposure and effect

Question 13

State four disadvantages of randomised control trials.

Answer 13

Randomized control trials can be costly
People who participate in RCTs may be very different from the rest of the population.
Randomized control trials usually focus on a specific, narrow research question related to a certain treatment or medication and a specific comparison with another treatment or exposure

Ethical considerations must be made when randomizing treatments or exposures

Question 14

True or false: it is not possible to use RCTS to test effects of exposures that are expected to be harmful, for ethical reasons.

Answer 14

True

Question 15

What occurs in an observational study?

Answer 15

Researcher does not determine who is exposed, but rather observes the outcomes (no intervention)

Question 16

What is an observational study?

Answer 16

Documentation of a naturally occurring relationship between exposure and outcome, e.g., incidence of lung cancer in smokers versus non-smokers

Question 17

Name the four main types of observational study.

Answer 17

Cross-sectional

Cohort

Case-control

Ecological

Question 18

Describe cohort studies.

Answer 18

Determine exposure
Observe if illness occurs
Often called incidence studies
Involves groups of individuals who share similar characteristics (same school, same occupation, etc.)
In cohort studies, participants are divided into two groups: ‘exposed’ and ‘unexposed’
Individuals undergo observation, to determine ‘disease’ or ‘no disease’

Question 18

State two features of a cross-sectional study.

Answer 18

Surveys both exposure and disease of individuals at a particular time

Demonstrates the relationship between disease and exposure, or non-exposure

Question 19

____________ studies can be retrospective or prospective.

Answer 19

Cohort

Question 20

True or false: a case-control study is usually conducted before a cohort or an experimental study to identify the possible aetiology of the disease.

Answer 20

True

Question 21

A _____________ study is preferred when the disease is rare because investigators can intentionally search for the cases.

Answer 21

Case-control

Question 22

Describe case-control studies.

Answer 22

Identify ill cases and comparison group
Compare exposures
Used to retrospectively determine if there is an association between an exposure and a specific health outcome.
Proceed from effect (e.g., health outcome, condition, disease) to cause (exposure)
Collect data on exposure retrospectively
Are observational studies because no intervention is attempted, and no attempt is made to alter the course of the disease

Question 23

A ____________ study involves comparing individuals with a particular condition or disease (cases), to a group of individuals with the same general characteristics, but without the condition or disease (controls).

Answer 23

Case-control

Question 24

Outline the first steps of designing a case-control study.

Answer 24

Firstly, a hypothesis is determined
Identification of cases
Eligibility criteria
Case definition
Age, gender, etc.
Criteria or definition clearly defined

Sources of cases need to be clearly defined

Question 25

What types of controls can be used in case-control studies?

Answer 25

Hospital controls
Dead controls
Friends and neighbours
Population controls

Multiple control groups

Question 26

True or false: cases for case-control studies can often be limited by rarity of disease.

Answer 26

True

Question 27

How is exposure measured in case-control studies?

Answer 27

Assess prior exposure (exposure to possible risk factors; the frequency and exposure in both ‘case’ and ‘control’ groups are compared) status at some specified time point before disease onset

The procedures used for the collection of exposure data should be the same for cases and controls

Question 28

List seven methods of measuring exposure.

Answer 28

Standardised questionnaires
Biological samples
Interviews with the subject
Interviews with spouse or other family members
Medical records
Employment records

Pharmacy records

Question 29

What is recall bias?

Answer 29

When the recall is better among cases than controls because of the presence of the disease

Question 30

Controls are used to provide an estimate of the exposure rate in the population. Therefore, ___________ _______ may occur when those individuals selected as controls are unrepresentative of the population that produced the cases.

Answer 30

Selection bias

Question 31

Identify advantages of case-control studies.

Answer 31

Cost effective relative to other analytical studies such as cohort studies
Case-control studies are retrospective, and cases are identified at the beginning of the study; therefore, there is no long follow-up period (as compared to cohort studies)
Efficient for the study of diseases with long latency periods
Allow examination of multiple exposures simultaneously
Useful as initial studies, to establish an association

Question 32

Outline disadvantages of case-control studies.

Answer 32

Particularly prone to bias, especially selection, recall and observer bias because they rely on memory and people with a condition will be more motivated to recall risk factors
Case-control studies are limited to examining one outcome
Unable to estimate incidence rates of diseases (unless study is population based)
Poor choice for the study of rare exposures
The temporal sequence between exposure and disease may be difficult to establish

It can be difficult to find a suitable control group

Question 33

State two features of ecologic studies.

Answer 33

Compare populations, rather than individuals

Cannot link a factor and a disease at individual level