Clinical characteristics of high-altitude interstitial lung disease: a two-center, retrospective, observational study

The impact of high altitude on patients with interstitial lung disease (ILD) remains unclear. This study aimed to describe the clinical characteristics of ILD patients in high-altitude regions. This retrospective observational study included patients diagnosed with Idiopathic Pulmonary Fibrosis (IPF) and Connective Tissue Disease-associated ILD (CTD-ILD) hospitalized at two hospitals in Qinghai and Tibet between April 2018 and September 2021. Patients were categorized into high-altitude (≥ 2500 m) and low-altitude (< 2500 m) groups. Demographic, clinical, hematological, and pulmonary function data were collected and analysed. A total of 119 patients were enrolled, with 56 in the high-altitude group and 63 in the low-altitude group. Compared with the low-altitude group, the high-altitude group had a significantly greater proportion of CTD-ILD patients (42.2% vs. 82.1%, p < 0.001). Patients in the high-altitude group presented higher red blood cell counts and hemoglobin and hematocrit levels but lower PaO2/FiO2 ratio (P/F ratio), FVC, and DLCO. This study revealed a higher prevalence of CTD-ILD, an increased proportion of Tibetan ethnicity, differences in the P/F ratio, MCV, FVC, MCHC, and HGB levels in the high-altitude group.