Introduction to Epidemiology Flashcards
What is epidemiology?
The study of that which fall upon people.
What are examples of denominators?
Health board, city, hospital and disease register.
Why is the denominator important in epidemiological studies?
Without a denominator, population and time death rates are meaningless.
Define prevalence.
Proportion of population that has the disease.
What does incidence identify?
Useful for identifying causes of diseases.
What does prevalence identify?
Identifies disease burden.
When does incidence occur?
By definition, only in people without the disease.
Define sporadic.
Occasional cases occurring irregularly.
Define endemic.
Persistent background level of occurrence.
Define epidemic.
Occurrence in excess of the expected level for a given time period.
Define pandemic.
Epidemic occurring in or spreading over more than one continent.
What are examples of non-modifiable exposures?
Age, sex and genotype.
What are examples of modifiable exposures?
Smoking, weight, diet and alcohol consumption.
What are examples of interventions?
Drug therapy, surgery and lifestyle advice.
What is the risk equation?
(Number of outcomes in a group/number of people in a group) x 100.
What is the relative risk equation?
Risk in exposed/risk in unexposed.
What is the relative risk reduction equation?
(1-relative risk)x100.
What is the absolute risk reduction equation?
Risk in unexposed-risk in exposed.
What is the number needed to treat equation?
1/absolute risk reduction.
When is the odds ratio used?
Commonly used estimate of risk ratio.
What is rate ratio?
Ratio between two mortality rates, hospitilisation rates.
What is the hazard ratio?
A special kind of rate ratio (survival analysis).
What are confidence intervals?
A range of plausible values.
What does the confidence interval tell you?
Values near the limits are less plausible than those in the middle and the wider the interval the greater the uncertainty.
When are confidence intervals useful?
Very useful in appraising published research.
What would you do in a cross-sectional study?
Sample a population.
What would you do in a case-control study?
Select cases with an outcome, but select controls without an outcome.
What would you do in a cohort study?
Select people without an outcome.
What would you compare in a cohort study?
Risk of disease in exposed and unexposed.
What would you compare in a randomised controlled trial?
Compare risk of outcome in intervention and control groups.
What is the objective in a randomised controlled trial?
Treatment effect.
What is the objective in a cohort study?
Cause, prognosis and incidence.
What is the objective in a case-control study?
Cause.
What is the objective in a cross-sectional study?
Prevalence
Which study designs look into the future?
RCT and cohort.
What are the 2 types of cohort study?
Retrospective an prospective.
Which study designs look into the past?
Case-control and cross-sectional.
When is a causal link more likely?
With strong associations, in different studies and different sub-groups.
How is specificity linked to causal links?
A causal link is more likely when a disease is associated with one specific factor.
How is temporality linked to causal links?
A CL is more likely if exposure to the putative cause has been shown to precede the outcome.
How is a biological gradient linked to causal links?
A CL is more likely if different levels of exposure to the putative factor lead to different risk of acquiring the outcome.
How is plausibility linked to causal links?
A CL is more likely if a biologically plausible mechanism is likely or demonstrated.
How does coherence effect causal links?
A CL is more likely if the observed association conforms with current knowledge.
How does experiment effect causal links?
A CL is very likely if removal of the putative factor leads to a reduced risk of acquiring the outcome.
How does analogy effect causal links?
A CL is more likely if an analogy exists with other diseases, species or settings.
