Modeling the Effects of Smoking on Lung Cancer.

Modeling the effect of smoking on the risk of lung cancer in cohort studies requires specification of time-dependent exposure variables and appropriate handling of confounding. This can be challenging as data on both exposure and confounders are typically incompletely observed. We discuss population exposure and disease processes and review modeling challenges when exposures are dynamic and challenging to summarize. Biases arising from failure to address time-dependent confounding are highlighted, with particular reference to a paradox related to the effect of quitting on risk of lung cancer. We stress the utility of comprehensive joint models.