Association between the severity of interstitial lung disease and the risk of osteoporotic vertebral fractures in patients with rheumatoid arthritis

This study aimed to investigate the relationship between interstitial lung disease (ILD) severity and bone mineral density (BMD) and osteoporotic vertebral fractures (OVFs) in patients with rheumatoid arthritis (RA) and determine whether ILD independently affects skeletal health. This retrospective cross-sectional study included 150 RA patients treated between January 2021 and December 2024. Based on high-resolution chest computed tomography, patients were classified as RA-ILD (n = 62) or RA without ILD (n = 88). RA-ILD cases were further stratified by fibrosis extent into mild (<20%, n = 27), moderate (20%-50%, n = 24), and severe (>50%, n = 11). Demographic data, clinical features, inflammatory markers, vitamin D, bone turnover indices, and medication exposure, including cumulative glucocorticoid dose, were collected. BMD at the lumbar spine, total hip, and femoral neck was measured by dual-energy X-ray absorptiometry. OVF was assessed by thoracolumbar radiography or computed tomography using the Genant semiquantitative method. Group comparisons, trend analyses, correlation analyses, and multivariable logistic regression were performed to identify independent risk factors for OVF. ILD was present in 41.3% of RA patients. Compared with those without ILD, RA-ILD patients were older, had longer disease duration, higher disease activity, elevated C-reactive protein/erythrocyte sedimentation rate, lower 25-hydroxyvitamin D, higher bone alkaline phosphatase levels, and greater cumulative glucocorticoid exposure (all P < .05). Lumbar spine, total hip, and femoral neck BMD were significantly lower in the RA-ILD group, accompanied by a lower lumbar T-score. OVF prevalence was higher in RA-ILD patients (30.6% vs 14.8%), including more multiple fractures. Within the RA-ILD cohort, BMD declined progressively with increasing ILD severity, and pulmonary function indices (forced vital capacity [%] and diffusing capacity for carbon monoxide [%]) showed positive correlations with BMD. OVF frequency rose stepwise from mild to severe ILD (14.8%, 29.2%, and 54.5%). Multivariable analysis identified ILD severity as an independent predictor of OVF (odds ratios = 2.51, 95% confidence interval: 1.21-5.22), together with age and cumulative glucocorticoid exposure. RA patients with ILD exhibit significantly reduced BMD and an increased risk of OVFs, which worsen with ILD severity. ILD appears to be an independent risk factor for skeletal deterioration in RA, highlighting the importance of early bone health assessment and preventive management in this population.