Steroid myopathy in patients with chronic respiratory diseases.

Background: Corticosteroid-induced myopathy is a well known clinical entity, and experimental studies showed decreased rate of protein synthesis and increased rate of protein breakdown in muscles of chronically treated animals.

Objective: The present observational study was aimed to evaluate skeletal muscle functions in asthmatics and patients with other chronic respiratory diseases treated by inhaled or oral corticosteroids.

Methods: Thirty six patients with respiratory diseases were included into the study. The physician-rated peripheral motor deficits scale, stepper test and ankle/wrist index were used for assessment of muscle functions. The effects of length of glucocorticoids intake on muscle functions were evaluated.

Results: Sixty five per cent of patients using corticosteroids daily during 1 year and longer reported weakness in legs, and 20% of these patients demonstrated objective signs of the muscle weakness. The performance on the stepper test was significantly worse in patients chronically using corticosteroids in comparison with the control group (10.9 ± 3.4 steps vs 16.1 ± 2.4 steps per 10s, respectively; F=21.6, p<0.001). In addition, a proportion of patients using corticosteroids for at least 18 months were characterized by muscle hypotrophy at a dominant leg.

Conclusion: Chronic intake of inhaled corticosteroids induces clinically significant decrease of muscle functions at least after 1-year of daily treatment.