Gender disparities in rehospitalisations after coronary artery bypass grafting: evidence from a sparse functional causal mediation analysis of the MIMIC-IV data

TL;DR

This study investigates how gender influences rehospitalisation rates after CABG surgery, revealing that women experience higher rehospitalisations partly due to differences in postoperative central venous pressure, using advanced causal mediation analysis.

Contribution

It introduces a novel quasi-Bayesian Monte Carlo method to analyze causal mediation with sparse functional mediators and zero-inflated outcomes in medical data.

Findings

Women have higher rehospitalisation rates post-CABG.

Time-varying central venous pressure mediates gender effects.

A new statistical method effectively handles sparse and zero-inflated data.

Abstract

Hospital readmissions following coronary artery bypass grafting (CABG) not only impose a substantial cost burden on healthcare systems but also serve as a potential indicator of the quality of medical care. Previous studies of gender effects on complications after CABG surgery have consistently revealed that women tend to suffer worse outcomes. To better understand the causal pathway from gender to the number of rehospitalisations, we study the postoperative central venous pressure (CVP), recorded over the first 24 hours of patients' intensive care unit (ICU) stay after the CABG surgery, as sparse observations of a functional mediator. Confronted with time-varying CVP measurements and zero-inflated rehospitalisation counts within 60 days following discharge, we propose a parameter-simulating quasi-Bayesian Monte Carlo approximation method that accommodates a sparse functional mediator and a zero-inflated count outcome for causal mediation analysis. We find a causal relationship between the female gender and increased rehospitalisation counts after CABG, and that time-varying central venous pressure mediates this causal effect.