Epidemiological Studies Flashcards
List four applications of epidemiological studies.
Clarify clinical and demographic characteristics
Identify which populations are at risk
Provide clues to cause of disease
Guide in preventative measures and interventions
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.
Hypothesis
Outline descriptive studies.
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.)
List three forms of descriptive study.
Case report
Case series
Incidence study
What two values do descriptive studies principally measure?
Prevalence and incidence
What is the aim of analytical epidemiology?
Attempts to provide the ‘why’ and ‘how’ of such health-related events, by comparing groups of individuals
Name three epidemiological determinants.
Agents
Hosts
Environments
__________ epidemiology attempts to determine the cause of an outbreak.
Analytical
Experimental analytical epidemiology is also called _____________ epidemiology.
Interventional
Describe experimental epidemiology.
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
What is a randomised control trial?
A design with subjects randomly assigned to treatment and comparison groups
List three advantages of randomised control trials.
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
State four disadvantages of randomised control trials.
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
True or false: it is not possible to use RCTS to test effects of exposures that are expected to be harmful, for ethical reasons.
True
What occurs in an observational study?
Researcher does not determine who is exposed, but rather observes the outcomes (no intervention)
What is an observational study?
Documentation of a naturally occurring relationship between exposure and outcome, e.g., incidence of lung cancer in smokers versus non-smokers
Name the four main types of observational study.
Cross-sectional
Cohort
Case-control
Ecological
Describe cohort studies.
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’
State two features of a cross-sectional study.
Surveys both exposure and disease of individuals at a particular time
Demonstrates the relationship between disease and exposure, or non-exposure
____________ studies can be retrospective or prospective.
Cohort
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.
True
A _____________ study is preferred when the disease is rare because investigators can intentionally search for the cases.
Case-control
Describe case-control studies.
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
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).
Case-control
Outline the first steps of designing a case-control study.
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
What types of controls can be used in case-control studies?
Hospital controls
Dead controls
Friends and neighbours
Population controls
Multiple control groups
True or false: cases for case-control studies can often be limited by rarity of disease.
True
How is exposure measured in case-control studies?
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
List seven methods of measuring exposure.
Standardised questionnaires
Biological samples
Interviews with the subject
Interviews with spouse or other family members
Medical records
Employment records
Pharmacy records
What is recall bias?
When the recall is better among cases than controls because of the presence of the disease
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.
Selection bias
Identify advantages of case-control studies.
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
Outline disadvantages of case-control studies.
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
State two features of ecologic studies.
Compare populations, rather than individuals
Cannot link a factor and a disease at individual level
