Quantitative assessment of erector spinae muscles in patients with Mycobacterium avium complex lung disease

Background and objective: No reports exist regarding skeletal muscle involvement in patients with Mycobacterium avium complex lung disease (MAC-LD). The cross-sectional area of the erector spinae muscles (ESMCSA) reflects physical activity and can be assessed by computed tomography (CT). We investigated the relationship between ESMCSA and physiological parameters and prognosis in MAC-LD patients. Material and methods: In this prospective observational study, the ESMCSA was measured on single-slice axial CT images. MAC-LD patients and sex-and age-matched controls (non-MAC-LD participants) were evaluated. We evaluated the relationship between the ESMCSA and physiological parameters and prognosis. Results: A total of 260 patients (209 female; median age, 69 years; 190 with nodular/bronchiectatic disease; 74 with cavitary lesions) were enrolled. The ESMCSA was not different between MAC-LD patients and controls. In MAC-LD patients, the ESMCSA was significantly associated with age, body mass index (BMI), pulmonary function, CT severity, and health-related quality of life (HRQL). Multivariate Cox proportional hazards analyses revealed that an ESMCSA < -1 standard derivation (hazards ratio [HR], 2.76; P = 0.047) was significantly associated with all-cause mortality, along with BMI < 18.5 kg/m(2) (HR, 3.67; P = 0.02) and presence of cavitary lesions (HR, 5.84; P = 0.001). However, the ESMCSA was not significantly associated with all-cause mortality when current treatment status, % predicted functional vital capacity, and forced expiratory volume in 1 s were added to the analyses. Conclusions: Although the prognostic impact was limited, ESMCSA was significantly associated with HRQL and prognostic physiological parameters, such as BMI and pulmonary function.