Abstract
BACKGROUND: This study investigates the impact of type 2 diabetes mellitus (T2DM) on the risk of interstitial lung disease (ILD) and its subtypes in patients with rheumatoid arthritis (RA). RA is often complicated by ILD. T2DM has systemic proinflammatory effects, but its impact on RA-related ILD is unclear. This research aims to elucidate the interplay between these conditions to inform clinical management and patient care strategies. AIM: To determine if RA patients with T2DM have a higher occurrence of ILD compared to RA patients without T2DM. METHODS: We conducted a retrospective cohort study using the 2019-2020 National Inpatient Sample. Adult RA patients with and without T2DM were identified via International Classification of Diseases, 10(th) Revision (ICD-10) codes. Propensity score matching (1:1) balanced 15+ confounders. Logistic regression assessed the association of T2DM with ILD (overall and by subtype) and secondary outcomes (acute respiratory distress syndrome, pneumothorax, pleural effusion, pulmonary hypertension). Missing data were excluded. ILD subtypes were included based on ICD-10 codes and case count. RESULTS: Among 199380 RA inpatients, ILD was more common in those with T2DM (2.25%) vs without (1.11%). After matching (n = 121046), ILD remained higher in RA + T2DM [odds ratio (OR) = 2.02, 95%CI: 1.84-2.22, P < 0.001], with an absolute risk increase of about 1.14%. T2DM was associated with higher odds of ILD subtypes including usual interstitial pneumonia (OR = 3.20) and non-specific interstitial pneumonia (OR = 3.50). Other subtypes showed elevated ORs; eosinophilic pneumonia showed an inverse association (OR = 0.23). PAH and pneumothorax were also more common in RA + T2DM (OR = 1.40 and 1.85, respectively). Acute respiratory distress syndrome and pleural effusion rates did not differ by T2DM status. Rare subtype findings should be interpreted cautiously. CONCLUSION: T2DM increases ILD risk in RA and is linked to higher rates of pulmonary hypertension and pneumothorax, suggesting a role in exacerbating RA-related lung complications.