Fundamentals of epidemiology - an evolving text - Are you looking ...

MAIN POINTS
Confounding is a distortion or misattribution of effect to a particular study factor. It results
from noncomparability of a comparison group.
A confounder is a determinant of the outcome or its detection, or possibly a correlate of a
determinant, that is unequally distributed between groups being compared.
A determinant of the disease should appear as an independent risk factor, i.e., not one whose
association with disease results from its association with the study factor.
A potential confounder (i.e., a disease determinant) need not be an actual confounder – an
actual confounder must be associated with the study factor.
Confounding can be controlled in the study design and/or analysis.
Control through the study design is accomplished through restriction, matching
(prestratification), or randomization.
Control in the analysis is accomplished through stratified analysis and/or mathematical
modeling.
Adequacy of control is compromised by errors in the conceptualization, measurement,
coding, and model specification for potential confounders.
Confounding deals with "guilt" or "innocence"; effect modification deals with "conspiracy".
Discovery that an association arises from confounding does not make it less "real", but does
change its interpretation.
The crude association is real and for some purposes is the relevant measure.
_____________________________________________________________________________________________
www.epidemiolog.net, © Victor J. Schoenbach 2000 11. Multicausality: Confounding - 369
rev. 10/28/2000, 11/2/2000, 5/11/2001