Characteristics and Impact of Peripheral and Respiratory Muscle Weakness in Patients With Interstitial Lung Disease: A Cross-Sectional Observational Study.

Abstract

Background: Muscle weakness is a clinically significant complication of interstitial lung disease (ILD) that worsens dyspnea, fatigue, and quality of life, but its epidemiology and clinical impact remain understudied.

Methods: In this cross-sectional study of 107 ILD patients, peripheral muscle weakness was defined as handgrip strength (HGS) < 28.0 kg (males) or < 18.0 kg (females), and respiratory muscle weakness as maximal inspiratory pressure (MIP) < 80% predicted. Assessments included pulmonary function, echocardiography, diaphragm ultrasound, 6-min walk distance (6MWD), short physical performance battery (SPPB), quality of life, and psychological status. Multivariate logistic regression identified the predictors of muscle weakness.

Results: Peripheral muscle weakness (66.4%) was associated with older age, lower BMI, worse pulmonary function, reduced 6MWD, and higher right ventricular systolic pressure (RVSP) (all p < 0.05). Calf circumference (OR 0.774, 95% CI 0.659-0.910) and 6MWD (OR 0.991, 95% CI 0.985-0.998) independently predicted peripheral weakness. Respiratory muscle weakness (46.7%) correlated with older age, lower BMI, impaired lung function, and higher peripheral weakness rates. Biomass fuel exposure (OR 7.855, 95% CI 1.587-38.890) and 6MWD (OR 0.742, 95% CI 0.648-0.850) were significant determinants. Both weakness types led to significant declines in diffusion capacity, physical function, and quality of life (p < 0.05), without ILD subtype differences.

Conclusion: ILD patients with muscle weakness show impaired lung function, reduced physical capacity, and poorer quality of life. Calf circumference and 6MWD influence peripheral weakness, while biomass exposure and grip strength influence respiratory weakness.