30. Epidemiology Flashcards
Define ‘epidemiology’
- scientific method of studying disease in populations
- study of distribution and determinants of disease frequency in human populations
- in dentistry, includes measurement of dental disease in populations, evaluates effectiveness of treatment and assess needs/demands
3 components of epidemiology
- distribution
- frequency
- determinants
What is distribution in epidemiology?
- who is getting a disease?
- where/when is it occurring?
- are there patterns of disease?
What is frequency in epidemiology?
- quantification of existence and occurance of disease
What is determinants in in epidemiology?
- derived from data obtained from distribution and frequency
- necessary to test an epidemiologic hypothesis
Process of epidemiology
- a suspicion exists that a particular factor may be influencing occurrence of a disease (your suspicion may arise from clinical practice, observation, research)
- formulation of a specific hypothesis
- hypothesis is tested in epidemiological studies with comparison group
- collect and analyse data to determine whether a statistical association exists
- assess validity of any observed association by excluding alternative explanations like chance, bias, confounding etc
- does statistical association suggest a causal relationship?
What is looked at to see if statistical association suggests a causal relationship?
- magnitude of association
- other studies
- consistency of findings against other studies
- biological credibility
Ways to measure disease
- indices
- standardisation
- quantify it
- indirectly - evaluation of effectiveness
A ‘gold standard’ measure of dental disease would be …
- valid
- reliable
- objective
- simple
- reproducible
- quantifiable
- sensitive
- accceptable
List descriptive study designs
- observational
- case-reports
- case-series
- cross-sectional
Give analytic study design
- observational - case-control, cross-sectional
- experimental - clinical trials
Give study designs from bottom to strongest methodology
- animal and lab research
- case reports/case series
- case control studies
- cohort studies
- randomized controlled trials
- systematic reviews
- meta-analysis
Case-studies/case-series are used for …
- highlighting interesting or novel cases/treatment
- recognition of new disease/outcome
- formulation of new hypotheses
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
Define ‘case-report/case-series’
a report on a single patient or series of patients with an outcome of interest
- no control group required
What is a cross sectional study?
- observation of a defined population at a single point in time (or time-interval)
- exposure and outcome are determined simultaneously
Cross sectional surveys are used for …
- measuring prevalence of disease
- look at potential risk factors or cause
Disadvantages of cross sectional surveys
- may establish association, NOT causality
- confounders may be unequally distributed
- group sizes may be unequal
- recall bias
What’s a cohort studies?
- involves identification of two groups (cohorts) of patients
- one which received the exposure of interest
- one which did not
- and following these cohorts forward to assess the outcome of interest
Cohort studies are used for …
- measures the incidence of disease
- looking at causes of disease
- determining prognosis
- establishing timing and directionality of events
Disadvantages of 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 is a case-control study?
- a study which involves identifying patients who have the outcome of interest (case)
- and patients without same outcome (controls)
- looking back in time to see if they had the exposure of interest
Case-control studies are used for …
- looking at potential causes of disease
- suitable for rare diseases
Disadvantages of case-control studies
- confounders
- selection of controls may be difficult
- recall and selection bias
- difficult to establish time relationships between exposure to risk factor and development of disease
Randomised Controlled Trials are used for …
evaluating the effectiveness of an intervention
Disadvantages of randomised controlled trials
- high costs
- ethical issues
- participant compliance
How are randomised controlled trials random?
- exposure status assigned by researcher preferably by random allocation
- best way to reduce selection bias between 2 groups of participants
Define ‘systematic reviews’
- 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 evidence
Why do a systematic review?
- can end confusion
- highlight where there isn’t enough evidence
- yield new insights by combining findings from different studies
Key features of a systematic review
- needs to be an analysis of evidence not just a review
- question needs to be defined precisely defining population and outcomes so studies included are appropriate and comparable
- complete methods available detailing comprehensive searching for all evidence and author quality guidelines
