Causality Flashcards
What does it mean if a cause is sufficient
Can cause the disease on its own
What does it mean if something is a necessary cause?
It must always precede the disease
What is a cause?
An exposure or factor that increases the probability of disease
What can make something appear to be the cause when it isn’t?
Bias
Chance
Confounding
What is bias?
Deviation of the results or inferences of the truth, or processes leading to such deviation.
What is selection bias?
Systematic differences in the characteristics of the groups being studied due to the way in which they were selected.
What is information bias?
Error due to systematic differences in the measurement or classification of subjects in the group being studied
What are the Bradford-Hill criteria for inferring causality?
Strength, specificity and consistency of association Temporal sequence Dose response Reversibility Coherence of theory Biological plausibility Analogy
Bradford-Hill criteria - what is strength of association?
Causal link is more likely with strong associations (usually measured by rate ratio or OR)
BHC - what is specificity of association?
A causal link is more likely when an outcome is associated only with a specific factor and vice versa - ie only one cause/outcome
What is consistency of association?
More likely if observed in different studies or sub-groups
What is temporal sequence? (BHC)
The causal link is more likely if the exposure has been shown to come before the outcome
What studies are best for showing temporal sequence
Randomised control trials
Prospective cohort study
BHC - what is dose response?
A causal link is more likely if different levels of exposure to the factor leads to different risk of acquiring the outcome
BHC - what is reversibility?
A causal link is very likely if removal or prevention of the factor leads to a reduced or non-existent risk of acquiring the outcome.
