Confounding by Indication in Clinical Research

Abstract

In the assessment of the effect of a treatment or potential risk factor—termed an exposure—on a patient outcome, the possibility of confounding by other factors must be considered.¹ For example, if researchers studied the effect of coffee drinking on the development of lung cancer, they might observe an apparent association between these 2 variables. However, because drinking coffee is also related to smoking, the observed association between coffee drinking and lung cancer does not represent a true causal relationship but is rather the result of the association of coffee drinking with smoking—the confounder—which is the true cause of lung cancer.