Cumulative Versus Recent Smoking Exposure and Community-Acquired Pneumonia Severity: A Cross-Sectional Study

Abstract

Cigarette smoking may influence the severity of community-acquired pneumonia (CAP), but the relative contributions of cumulative smoking exposure, recent exposure, and pulmonary function remain unclear. This study examined associations of pack-years, exhaled carbon monoxide (eCO), and spirometric parameters with CAP severity. This analytical cross-sectional study included 57 adults hospitalised with CAP in Makassar, Indonesia, from June to July 2026. Smoking exposure, eCO category, spirometry, and Pneumonia Severity Index (PSI) were assessed. Associations with PSI score and ordinal CAP severity were evaluated using Spearman correlation and proportional-odds ordinal logistic regression. Thirty-nine participants were active smokers and 18 had passive smoke exposure. Among active smokers, pack-years correlated positively with PSI score (ρ=0.405, p=0.010) and ordinal CAP severity (ρ=0.398, p=0.012). After adjustment for FEV₁, body mass index, and occupational dust/smoke exposure, each 5-pack-year increase was associated with higher CAP severity (adjusted odds ratio [aOR] 1.32, 95% CI 1.05–1.67; p=0.017). eCO distribution differed significantly between active and passive exposure groups (p<0.001), but eCO was not independently associated with CAP severity (aOR 2.30, 95% CI 0.89–5.94; p=0.086). Most spirometric parameters were not associated with severity. Cumulative smoking burden showed the most consistent association with CAP severity, whereas recent eCO exposure and acute spirometric measurements were less informative.