Association of the Charlson Comorbidity Index and Age-Adjusted Charlson Comorbidity Index with Clinical Course and Mortality in Patients with Idiopathic Pulmonary Fibrosis

Background/Objectives: Idiopathic pulmonary fibrosis (IPF) frequently coexists with comorbidities that may influence clinical outcomes. The Charlson Comorbidity Index (CCI) quantifies the weighted comorbidity burden, whereas the age-adjusted Charlson Comorbidity Index (ACCI) additionally incorporates age. We evaluated the associations of CCI and ACCI with pulmonary function, disease severity, clinical course, and mortality in IPF. Methods: This retrospective, single-center cohort study included 319 patients with IPF. Comorbidities present at diagnosis were scored using the CCI and ACCI. Associations with pulmonary function, GAP index, acute exacerbations, hospitalization, long-term oxygen therapy, echocardiographic findings suggestive of pulmonary hypertension, incident malignancy, antifibrotic treatment, and mortality were assessed. Correlation analyses were performed using Spearman’s rank correlation coefficient, and Bonferroni correction was applied to account for multiple testing. Multivariable Cox proportional hazards regression was used to evaluate whether the CCI or ACCI was independently associated with survival. Time-to-event analyses were performed using Kaplan–Meier survival analysis.Results: The mean age was 71 ± 8 years, 78.1% were male, and 75.5% had at least one comorbid condition among patients with available comorbidity data. The median CCI and ACCI scores were 2 (IQR, 0–4) and 5 (IQR, 4–7), respectively. Higher CCI and ACCI categories were associated with hospitalization (p = 0.006 and p = 0.011), echocardiographic findings suggestive of pulmonary hypertension (both p = 0.002), and incident malignancy (p< 0.001 and p = 0.005, respectively). After Bonferroni correction, higher CCI and ACCI categories remained significantly associated with echocardiographic findings suggestive of pulmonary hypertension (both p = 0.002) and incident malignancy (both p< 0.001), whereas the associations with hospitalization did not remain statistically significant. A nominal association between ACCI and mortality (p = 0.044) also did not remain significant after Bonferroni correction. In Spearman analyses, ACCI remained significantly correlated with current age, age at IPF diagnosis, and the GAP index after correction, whereas the correlations of CCI and ACCI with baseline DLCO did not. Neither CCI (HR = 1.029, 95% CI: 0.923–1.146; p = 0.610) nor ACCI (HR = 1.035, 95% CI: 0.936–1.144; p = 0.509) was independently associated with survival in multivariable Cox regression analyses. Lower baseline DLCO remained independently associated with survival in both Cox models (both p< 0.001).Kaplan–Meier survival curves were constructed according to the predefined CCI and ACCI score categories (0, 1–2, 3–4, and ≥5), and survival distributions across categories were compared using the log-rank test. Conclusions: CCI and ACCI were associated with selectedclinical characteristics in IPF, particularly echocardiographic findings suggestive of pulmonary hypertension and incident malignancy. However, neither index independently predicted survival after multivariable adjustment. These indices may complement, rather than replace, disease-specific physiological assessments in patients with IPF.