Abstract Background Anemia is a common systemic manifestation in interstitial lung disease (ILD), including idiopathic pulmonary fibrosis (IPF), yet longitudinal patterns of hemoglobin (Hb) change remain poorly characterized. Understanding Hb trajectories may provide insights into systemic disease burden and prognosis in ILD. Methods Data were drawn from the Korean National Health Insurance Service-Health Screening Cohort, covering the period from January 1, 2004, to December 31, 2019. This study included ILD patients who had at least two Hb measurements following their diagnosis. We conducted a 1:1 matched cohort of 674 patients with ILD (ICD-10: J841) and 674 controls without ILD, matched by age, sex, and index year. Hemoglobin levels from serial health screenings were analyzed using linear mixed-effects models with random intercepts. The interaction between time and ILD status was evaluated to assess differential Hb trajectories. Multivariable models were adjusted for demographic, clinical, and lifestyle factors, including body mass index (BMI), smoking, comorbidities, and Charlson Comorbidity Index (CCI). Subgroup and sensitivity analyses were conducted according to age (60 vs ≥ 60 years), sex, baseline Hb level. 95% confidence intervals were computed using profile likelihood, and p values were obtained from t tests with Satterthwaite’s approximation. Results Baseline characteristics were well balanced between groups (mean age 65.7 years, 72.3% male). Median follow-up was 3.0 years in ILD (IQR 2.2-3.9) and 2.3 years in controls (IQR 1.9-2.9); mean follow-up was 3.2 ± 1.35 vs 2.6 ± 1.08 years, respectively (p 0.0001). In the unadjusted model, Hb increased slightly over time in the ILD group but declined in controls (Figure 1). In the adjusted model, Hb levels declined over time in both groups, but the rate of decline differed significantly between ILD and controls (interaction β = +0.0707 g/dL per year; p = 0.0051). Higher BMI (≥25 kg/m², p 0.001) and elevated CCI scores (≥5, p 0.001) were independently associated with Hb variation. Subgroup analyses revealed consistent Hb trajectory differences across sex and age strata, though no significant effect modification by sex was observed. Among younger patients (60 years), the interaction term was not significant (p = 0.13). Conclusion This study provides evidence of distinct Hb trajectories in ILD patients compared to matched controls. These findings support the clinical value of longitudinal Hb monitoring in ILD and warrant further investigation into modifiers of Hb change. This abstract is funded by: None
Kim et al. (Fri,) studied this question.