Skip Navigation LinksHome > September 2014 - Volume 25 - Issue 5 > Attributing Effects to Interactions
doi: 10.1097/EDE.0000000000000096

Attributing Effects to Interactions

VanderWeele, Tyler J.; Tchetgen Tchetgen, Eric J.

Supplemental Author Material


During typesetting an error was introduced on Line 2 of the left column of p. 716. The denominator at the end of this line should read “RR11” rather than “RR11 – 1.” Likewise, on Line 7 of the same page, the denominator at the beginning of this line should read “RR11” rather than “RR11 – 1.” The journal and the authors regret the error.

Please see the letter “Alternative decompositions for attributing effects to interactions” in this issue of the journal for further extensions on decompositions for attributing effects to interactions.

Epidemiology. 26(3):e36, May 2015.

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A framework is presented that allows an investigator to estimate the portion of the effect of one exposure that is attributable to an interaction with a second exposure. We show that when the 2 exposures are statistically independent in distribution, the total effect of one exposure can be decomposed into a conditional effect of that exposure when the second is absent and also a component due to interaction. The decomposition applies on difference or ratio scales. We discuss how the components can be estimated using standard regression models, and how these components can be used to evaluate the proportion of the total effect of the primary exposure attributable to the interaction with the second exposure. In the setting in which one of the exposures affects the other, so that the 2 are no longer statistically independent in distribution, alternative decompositions are discussed. The various decompositions are illustrated with an example in genetic epidemiology. If it is not possible to intervene on the primary exposure of interest, the methods described in this article can help investigators to identify other variables that, if intervened upon, would eliminate the largest proportion of the effect of the primary exposure.

© 2014 by Lippincott Williams & Wilkins, Inc

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