# Correlation between smoking and delirium in patients with sepsis: A retrospective analysis utilizing the MIMIC database

## TL;DR

This study finds that smoking increases the risk of delirium in sepsis patients, partly due to higher carbon dioxide levels.

## Contribution

The study identifies a novel mediating role of PaCO2 in the smoking-delirium relationship in sepsis patients.

## Key findings

- Smokers with sepsis had a 34.8% delirium rate compared to 25.7% in non-smokers.
- Smoking was an independent risk factor for delirium (OR=1.44).
- Hypercapnia mediated 7.876% of the smoking-delirium effect.

## Abstract

This study aimed to examine the relationship between smoking and delirium in patients with sepsis and identify potential mediating mechanisms, utilizing data from the Medical Information Mart for Intensive Care-IV (MIMIC-IV) database.

A retrospective cohort analysis was conducted involving 10855 adult patients with sepsis. Multivariable logistic regression, propensity score matching (PSM), and inverse probability treatment weighting (IPTW) were applied to assess associations while controlling for confounders such as demographics, comorbidities, vital signs, and laboratory parameters. Causal mediation analysis (CMA) was employed to explore the mediating role of partial pressure of carbon dioxide (PaCO2). Subgroup and sensitivity analyses were performed to assess result robustness.

The incidence of delirium was significantly higher among smokers compared to non-smokers (34.8% vs 25.7%). Adjusted models identified smoking as an independent risk factor (OR=1.44; 95% CI: 1.28–1.61). These findings were validated through PSM (OR=1.35; 95% CI: 1.20–1.53) and IPTW (OR: 1.25, 95% CI: 1.18–1.32). Subgroup analyses affirmed associations across most strata. CMA indicated that 7.876% (95% CI: 4.433–13) of the effect of smoking on delirium was mediated by elevated PaCO2, with direct and indirect effects quantified at 0.0625 (95% CI: 0.0428–0.0800) and 0.0050 (95% CI: 0.0027–0.0081), respectively. Sensitivity analyses among ICU survivors yielded consistent results (OR=1.52; 95% CI: 1.34–1.72).

Smoking is independently linked to an increased risk of delirium in patients with sepsis, with hypercapnia partially mediating this relationship. These findings emphasize the importance of smoking cessation and targeted respiratory management in preventing delirium.