# Smoking as a Contributing Factor in the Development of Empyema

## TL;DR

This study found that smoking is linked to empyema cases not caused by oral bacteria, suggesting it may act as a contributing factor.

## Contribution

The study proposes a dual-pathway hypothesis for empyema development involving oral bacteria and smoking.

## Key findings

- Group B (non-oral bacteria or culture-negative) had a significantly higher smoking index than Group A (oral commensal bacteria).
- Empyema patients showed poorer oral hygiene compared to national dental health data, including higher periodontal disease prevalence.
- Smoking was associated with longer hospital stays and higher smoking index in Group B1 (non-oral bacteria).

## Abstract

Background and aim: Empyema is characterized by the accumulation of pus in the pleural cavity, often arising as a complication of pneumonia. This study aimed to evaluate oral health in patients with acute empyema and to explore whether oral bacteria or smoking status were associated with empyema development.

Methods: This retrospective study included 45 patients who underwent surgery for acute empyema at our hospital between July 2020 and July 2023. Based on pleural fluid cultures, patients were categorized into the following three groups: those with oral commensal bacteria (Group A), those with non-oral bacteria (Group B1), and culture-negative cases (Group B2). Oral health parameters were compared between groups.

Results: Of the 45 patients (mean age: 66.6 years; 38 males), 18 were classified as Group A, nine as Group B1, and 18 as Group B2. Group B had a significantly higher smoking index than Group A. Compared with national dental health data, empyema patients exhibited markedly poorer oral hygiene, including a higher prevalence of periodontal disease and bleeding on probing (BOP). The culture positivity rate was 40%, consistent with previous studies. Group B1 showed the longest hospital stays and the highest smoking index, while Group A had more treated teeth and lower tobacco exposure.

Conclusion: Smoking was associated with empyema cases not linked to oral bacteria, suggesting it may act as a cofactor rather than an independent causal pathway. These findings support a dual-pathway hypothesis in which empyema may develop either through pneumonia induced by oral bacteria or through secondary infection in smokers. Further studies incorporating genetic and immunological analyses are warranted.