THEME 2b Epidemiology Flashcards
define epidemiology
study of how often diseases occur in different groups of people and why
What are the 3 components of epidemiology?
- Distribution
- frequency
- deteminants (derived from data 1. and 2., neccesary to test an epidemiologic hypothesis
What is this the process of :
A suspicion exists that a particular factor may be influencing the occurrence of a disease. (Your suspicion may arise from clinical practice, observation, research etc).
Formulation of a specific hypothesis.
Hypothesis is tested in epidemiological studies with a comparison group.
Collect and analyse data to determine whether a statistical association exists.
Assess validity of any observed association by excluding alternative explanations such as chance, bias and confounding.
Does statistical association suggest a causal relationship? (Consider the magnitude of the association / other studies / consistency of findings against other studies / biological credibility)
epidemiology
How can you measure disease?
1) Indices
2) Standardisation
3) Quantifying disease
4) Indirectly: evaluation of effectiveness
What is the “gold standard” of measure? (8)
Valid Reliable Objective Simple Reproducible Quantifiable Sensitive Acceptable
What is the difference between studys that are 1) descriptive and 2) analytical
1]. DESCRIPTIVE
Observational
Case-reports
Case-series
Cross-sectional
2]. ANALYTIC
Observational: case-control, cross-sectional
Experimental: clinical trials
What better meta-analysis or systematic reviews?
meta-analysis
List these in order of which is generally better:
1) systemic reviews
2) cohort studies
3) randomized controlled trails
4) case control studies
5) animal and lab research
6) case reports/series
1) systemic reviews
2) randomized controlled trails
3) cohort studies
4) case control studies
5) case reports/series
6) animal and lab research
What is case control sutdies generally better than animal and laboratory research? (4)
- stonger methodology
- less bias
- controls for comparison
- fewer studies
What are case-studies/series used for?
Highlighting interesting or novel cases / treatment
Recognition of new disease/outcome
Formulation of new hypotheses
What are the disadvantages of case-studies/ case-series?
Cannot demonstrate valid statistical association
Lack of appropriate comparison group can obscure a relationship or suggest an association where none exists
what is a case-report?
A report on a single patient or a series of patients with an outcome of interest.
No control group is required.
e.g. patient revived after no pulpse found with severe hyperthermia
What is a cross sectional survey?
Observation of a defined population at a single point in time (or time interval).
Exposure and outcome are determined simultaneously.
What is a cross sectional survey used for?
Measure prevalence of a disease
Look at potential risk factors or cause
What are the weaknesses of a cross sectional survey
May establish association, NOT causality.
Confounders may be unequally distributed
Group sizes may be unequal
Recall bias
describe the 2 cohorts/groups in a cohort sutdie:
Involves identification of two groups (cohorts) of patients, one which received the exposure of interest, and one which did not and following these cohorts forward to assess the outcome of interest.
What is a cohort studie used for?
Measures the incidence of disease
Looking at causes of disease
Determining prognosis
Establishing timing and directionality of events
What are the disadvantages of a cohort studies?
Controls may be difficult to identify
Exposure may be linked to hidden confounder
Blinding is difficult
For rare diseases, large sample size is often necessary or a long follow up.
What sort of patients are used in case-control studies?
A study which involves identifying patients who have the outcome of interest (cases) and patients without the same outcome (controls), and looking back in time to see if they had the exposure of interest
What are case-control studies used for?
Looking at potential causes of disease (suitable for rare diseases)
What are the disadvantages of case-control studies?
Confounders
Selection of controls may be difficult
Recall and selection bias
Difficult to establish time relationships between exposure to the risk factor and development of the disease.
what is the difference between a case-control study and a cohort study?
case control study involve looking at a number of individauls who already have the disease, cohort study looks at helahty individuals and sees if they will develop the disease (issues if a very rare disease)
What are randomised contorlled trails used for?
Used for:
- Evaluating the effectiveness of an intervention.
what are the disadvantages of randomised controlled trials?
High costs
Ethical issues
Participant
compliance
What doe randomised control trails involve?
2) What is randomisation used?
Exposure status is assigned by the researcher, preferably by random allocation.
2) Randomisation is the best way of reducing selection bias between 2 groups of participants.
what is a systemic review?
The evidence from a number of studies can be gathered together in one report which pools and analyses all available data to assess the strength of the evidence.
Why should systemic reviews be conducted?
Systematic reviews can end confusion / highlight where there is not enough evidence / yield new insights by combining findings from different studies.
What is a well known systemic review in dentistry?
the cochran reviews
