Relationship Between Skeletal Muscle Weakness During Hospitalization and Health-Related Quality of Life in Patients With Acute Exacerbation of Interstitial Lung Disease: A Multicenter Prospective Study

Background: Skeletal muscle weakness impairs health-related quality of life (HRQOL) in patients with exacerbation of chronic pulmonary diseases; however, few studies have examined the prevalence of skeletal muscle weakness in patients with acute exacerbation of interstitial lung disease (AE-ILD). This study aimed to determine the prevalence of skeletal muscle weakness in patients with AE-ILD and the relationship between muscle weakness and HRQOL. Methods: This multicenter prospective study enrolled patients admitted for AE-ILD who underwent pulmonary rehabilitation during hospitalization from August 2023 to March 2024. We assessed skeletal muscle strength, 6-min walk distance (6MWD), activities of daily living (ADL) score, and HRQOL using the COPD Assessment Test (CAT). Skeletal muscle strength was measured using handgrip strength (HGS) at admission and discharge. Skeletal muscle weakness was defined as a difference in HGS (ΔHGS) < -2.7 kg or cut-off HGS values of < 11 kg in men and < 7 kg in women at discharge. The results of the two groups were compared using the Mann-Whitney U-test and the chi-square test. This study was approved by the Human Ethics Review Committee of our university (2023-37). Results: Forty patients with AE-ILD were enrolled (mean age 79 y, 30 men). All the patients were diagnosed with ILD, including idiopathic interstitial pneumonia (n = 24), connective tissue disease-related ILD (n = 8), or other (n = 8). The rate of skeletal muscle weakness during hospitalization was 22.5% (n = 9). HGS and 6MWD at discharge were significantly lower in the weakness group than in the non-weakness group (HGS, 10.8 kg vs 21.9 kg, P = .001; 6MWD, 90.0 m vs 287.5 m, P = .007). The proportion of patients with AE-ILD impaired ADL was higher in the weakness group than in the non-weakness group (77.8% vs. 33.0%, P = .03). CAT score was significantly higher in the weakness group than in the non-weakness group (24.0 points vs 13.0 points, P = .041). There were no significant differences in laboratory data (KL-6, SP-D, LDH, and P/F ratio), HGS, or ADL scores at admission. Conclusions: The prevalence of skeletal muscle weakness in patients with AE-ILD during hospitalization was 22.5%. Patients with skeletal muscle weakness experienced ADL impairment, lower exercise tolerance, and poor HRQOL during their hospital stay. Preventing muscle weakness in patients with AE-ILD could improve their quality of life after discharge.