Population Studies Flashcards
What is meant by evidence based medicine?
the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients
What are the 3 things that must be integrated when practicing EBM?
- individual clinical expertise
- the best available external clinical evidence
- patient values & expectations
What are the 5 A’s when practicing EBM?
- ask
- access
- appraise
- apply
- assess
What is involved in the ask and access stages of the 5 A’s?
ASK - formulate a research question
ACCESS - find and retrieve the best evidence
What is involved in the appraise and apply stages of the 5 A’s?
APPRAISE - consider the evidence for its validity & relevance
APPLY - integrate the results into clinical practice
What is involved in the assess stage of the 5 A’s?
evaluate the effectiveness
What are the 4 types of evidence?
- description
- prediction
- causal inference
- qualitative
What is meant by ‘description’ as a type of evidence?
What happened and who was affected?
e.g people with X had Y
What is meant by ‘prediction’ as a type of evidence?
What will happen and who will be affected?
e.g. people with X are more likely to have Y
What is meant by ‘causal inference’ as a type of evidence?
What will happen if…? Why were they affected?
e.g. if we changed X, how would it change Y?
What is meant by qualitative evidence?
What matters and why does it matter?
How can we effectively change X and should we change it?
What is meant by causal inference being ‘deterministic’?
The cause can be easily linked to a certain outcome
What is meant by causal inference being ‘probabilistic’?
predictions about future health are not always correct due to vast variation between individuals
e.g. smoker surviving to 100
Why are groups studied, opposed to individuals?
Studying individual people is useless with probabilistic events
People will respond differently to the same exposure
Why can an entire population not be studied?
What is studied instead?
It is impossible or impractical to study an entire population
Samples are studied instead to make a generalisation about the population
What is the difference between clinical research and population health research?
Clinical research focuses on helping individuals
PHR focuses on helping and understanding populations
What is the main definition of a population?
The total inhabitants of a given country or area
e.g. Europe, Leeds, LS6 postcode
What is the alternative definition of a population?
A group of people from which the sample was drawn
or it can be any collection of units e.g. hospitals in england
What is a census?
when the sample studied is the entire population
What defines a population-based study?
If the study population is the total population of a country or area
What defines an observational study?
Something which cannot be experimented on
Observations are made and inferences are made based on what is seen
What is a case report?
a clinician writes about an interesting case (e.g. new disease) in order for other people to recognise and learn from this experience
What is a case series?
a description of a sample of cases with the same disease
a case report on multiple individuals
What is the benefit of performing a case series?
It allows for description of natural history and prediction of prognosis
e.g. typical duration, survival and predictors of prognosis
What is a register-based study?
A form of case series that uses disease registers to collect information on individuals with rare diseases
What are disease registers?
they count and collect information on people diagnosed with a particular disease
Why can disease registers often be used for research studies?
They are population-based
The disease occurrence per population can be estimated
What is meant by a cross-sectional study?
The study of a group of people at a single point in time
“snapshot study”
What are the common ways to collect information in a cross-sectional study?
Directly surveying or measuring a group of people
Gathering routinely-collected data
What is the negative side of performing a cross-sectional study?
There is a preference to collecting as much data as possible
What does it mean by the results of a cross-sectional study being ‘stratified’?
The results can be broken down (stratified) into subgroups
e.g. age, sex, occupation etc.
What is meant by a cohort study?
Examining a group of people and collecting information repeatedly over a period of time
What are the 3 common variables that descriptive studies are stratified into to generate hypotheses?
- individual level characteristics
- area level characteristics
- temporal characteristics
What are examples of individual level characteristics?
- age
- sex
- socio-economic position
- ethnic group
- marital status
- occupation
What are examples of area level characteristics?
- countries
- regions
- latitude
- rural vs urban areas
- more vs less deprived areas
What are examples of temporal characteristics?
- secular trends (over time)
2. dynamic or seasonal trends (e.g. month, season, day of week)
What is meant by an ecological study?
A study that examines variations between geographical areas
What are the units of analysis in an ecological study?
the units of analysis are AREAS and not individual people
When are ecological studies useful?
They CANNOT be used for testing hypotheses, but are useful for generating hypotheses
How should the results of an ecological study be used?
They cannot be used to make clinically relevant inferences
More research is warranted to try and understand reasons for differences in certain areas
