11-22-2017 / 12h-13h — Exposure misclassification in environmental epigenetic studies: is DNA-methylation a mediator or a biomarker?

Invited by Hélène Jacqmin-Gadda – BIOSTATISTICS TEAM

Assessing whether epigenetic alterations mediate associations between environmental exposures and health outcomes is increasingly popular. We investigate the impact of exposure misclassification in such investigations.
We quantify bias and false positive rates due to exposure misclassification in mediation analysis and assess the performance of SIMEX correction approach. Further, we evaluate whether DNA-methylation mediates smoking-birth weight relationship in the MoBa birth cohort.
Ignoring exposure misclassification increases Type I error in mediation analysis. The direct effect is underestimated and, when the mediator is a biomarker of the exposure, as is true for smoking, the indirect effect is overestimated.
Misclassification correction plus cautious interpretation are recommended for mediation analyses in the presence of exposure misclassification.