MFD Theme 2b Flashcards
what is epidemiology
the scientific method of studying diseases in populations.
orderly study of diseases and conditions where the group and not the individual is the unit of interest.
study of the distribution and determinants of disease frequency in human populations.
what are the examples of epidemiology in dentistry
measurement of dental disease in populations & subgroups
evaluation of the effectiveness of treatments
assessment of needs and demands within the community
what are the 3 components of epidemiology
- Distribution
- Frequency
- Determinants
what is the process of epidemiology
suspicion
formulation of hypothesis
hypothesis tested in epidemiological studies with comparison group
Collect and analyse- statistical association
Assess validity of any observed association
Does statistical association suggest a causal relationship?
how can you measure disease to investigate epidemiology
Can use indices
Importance of standardisation
Quantification of disease
Need to be objective rather than subjective
what is the Gold standard measure for 12 Dental Disease
Valid, reliable, objective, simple to investigate, reproducible, sensitive & acceptable to the patient (i.e. must not cause harm to the patient).
Is everything you measure a true measure of that disease or is it just a proxy
Reproducible for everyone by standardisation and calibration where possible
Must calibrate to the gold standard we all see the same thing
Sensitive- minute or major improvements in a condition
Acceptable to the patient e.g. periodontal probing (do not press too hard)
what are the types of study design
1) Descriptive – observational/ case-reports / case-series / cross-sectional
2) Analytic – observational (case-control/ cross-sectional) OR observational (clinical trials).
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/weaknesses of case studies/series
- Cannot demonstrate valid statistical association
* Lack of appropriate comparison group can obscure a relationship or suggest an association where none exists
what is involved in a cross sectional survey
Observation of a defined population at a single point in time (or time interval)
Exposure and outcome are determined simultaneously
Used for measuring the prevalence of a disease/looking at potential risk factors or cause
Adult and children survey every year are a good example
Could be a period of time- still cross sectional
However cannot validate what you’ve been told
what are cross sectional surveys use for
Measure prevalence of a disease
look at potential risk factors or cause
what are the disadvantages of cross sectional surveys
- Can’t prove causality can only link potential association
- Confounders may be unequally distributed (a confounder is an unobserved exposure associated with the exposure of interest and is a potential cause of the outcome of interest)-
- Group sizes may be unequal
- Recall bias (recall something better that happened recently rather than long time ago)
what are cohort studies
Involves identification of two groups of patients
- one which received the exposure of interest
- one which did not
following these cohorts forward to assess the outcome of interest.
Prospective and work forwards
what are cohort studies used for
Measures the incidence of disease
Looking at causes of disease
Determining prognosis
Establishing timing and directionality of events
what are Disadvantages / weaknesses of cohort studies
Controls may be difficult to identify
Exposure may be linked to hidden confounder
Blinding is difficult- easy to know what group you’re in
For rare diseases large sample size is often necessary (very small % of people actually have the disease)
Cohort studies should be used for common diseases e.g caries, gingivitis
what are 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.
Look BACKWARDS in time – start with the disease and look back, unlike cohorts
Involves looking at their exposure to carcinogens/teratogens/wood-shavings
Looking then back at dental/medical records & occupations in order to try create a link between those who have the outcome
what are case control studies used for
Looking at potential causes of disease (suitable for rare diseases
what are Disadvantages/weaknesses of case control studies
Confounders e.g. if you don’t drink tap water, it doesn’t matter if its fluoridated
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
difference between case-control study and a cohort study
Case control involves investigating individuals who have already been infected with a disease
Cohort involves individuals who are initially disease free before the trial
what are Randomised Controlled Trials (RCTs)
Exposure status is assigned by the researcher (preferably by random allocation)
Randomisation is the best way of reducing selection bias between 2 groups of participants.
Best RCTS have qualitative component along-side asking people how they feel
Used for evaluating the effectiveness of an intervention
what are Randomised Controlled Trials (RCTs) Disadvantages:
High costs
Ethical issues
Participant compliance – e.g. drop out
what is a systematic review definition
The evidence from a number of studies (can be RCTS) can be gathered together in one report which pools and analyses all available data to assess the strength of the evidence
Why conduct a systematic review?
Systematic reviews can end confusion / highlight where there is not enough evidence/yield new insights by combining findings from different studies