Path-specific causal decomposition analysis with multiple correlated mediator variables

TL;DR

This paper introduces a flexible causal decomposition analysis method capable of handling multiple correlated mediators, improving bias reduction and confidence interval accuracy in health disparity studies.

Contribution

It extends existing methods by modeling multiple correlated mediators with a multivariate approach and clarifies causal assumptions for joint and path-specific effects.

Findings

Simulation study shows reduced bias and narrower confidence intervals.

Application reveals mediators' roles in Black-White diabetes disparities.

Method effectively handles binary and continuous mediators in health research.

Abstract

A causal decomposition analysis allows researchers to determine whether the difference in a health outcome between two groups can be attributed to a difference in each group's distribution of one or more modifiable mediator variables. With this knowledge, researchers and policymakers can focus on designing interventions that target these mediator variables. Existing methods for causal decomposition analysis either focus on one mediator variable or assume that each mediator variable is conditionally independent given the group label and the mediator-outcome confounders. In this paper, we propose a flexible causal decomposition analysis method that can accommodate multiple correlated and interacting mediator variables, which are frequently seen in studies of health behaviors and studies of environmental pollutants. We extend a Monte Carlo-based causal decomposition analysis method to this setting by using a multivariate mediator model that can accommodate any combination of binary and continuous mediator variables. Furthermore, we state the causal assumptions needed to identify both joint and path-specific decomposition effects through each mediator variable. To illustrate the reduction in bias and confidence interval width of the decomposition effects under our proposed method, we perform a simulation study. We also apply our approach to examine whether differences in smoking status and dietary inflammation score explain any of the Black-White differences in incident diabetes using data from a national cohort study.