Critical Thinking - Lecture Twenty-Seven Flashcards
Confounding I
Confounding
A mixing or muddling of effects when the relationship we are interested in is confused by the effect of something else – the confounder
Epi saying for confounding
Risk factors party together
Example given for confounding
If you tend to drink alcohol, you tend to smoker
When if confounding valid?
If groups equivalent for anything else associated with outcome
Three properties of potential confounder
Independently associated with the outcome
Independently associated with the exposure
Not on the causal pathway
Independently associated with the outcome
A risk (or protective) factor for the outcome regardless of exposure status
Independently associated with the exposure
Imbalance in distribution across exposure groups
Not on the causal pathway
Not how the exposure affects the outcome
What can confounding do?
Over/Under-estimatation of a true association, Change the direction of a true association and give appearance of an association when not one
Give appearance of an association when not one
Go from null to something else
Change direction of a true association
Risk factor becomes protective factor (and vice versa)
Harmful exposure: over-estimation
Confounding has resulted in an over-estimation of the true harmful effect of the exposure (association appears stronger than it really is, RR is ‘further away from the null’)
Harmful exposure: under-estimation
Confounding has resulted in an under-estimation of the true harmful effect of the exposure (association appears weaker than it really is, RR is ‘closer to the null’)
Beneficial exposure: over-estimation
Confounding has resulted in an over-estimation of the true protective effect of the exposure (association appears stronger than it really is, RR is ‘further away from the null’)
Beneficial exposure: under-estimation
Confounding has resulted in an under-estimation of the true protective effect of the exposure (association appears weaker than it really is, RR is ‘closer to the null’)
