Prolonged loss of intercostal muscle mass and its predictors in COVID-19 patients: A retrospective study from tertiary hospital.

Sarcopenia is a contributing factor in the development of long-COVID syndrome. We aimed to investigate how intercostal muscle mass changes over 3 months compared to other chest wall muscles following COVID-19 infection, along with identifying factors contributing to intercostal muscle loss during follow-up. We retrospectively studied 110 COVID-19 patients, analyzing muscle masses in the intercostal, pectoralis, and thoracic 12th vertebra level (T12) on initial and follow-up CT scans. Muscle mass was quantitatively assessed using density histogram analysis. We calculated the muscle difference ratio (MDR) as the following formula: (initial muscle mass - follow-up muscle mass)/initial muscle mass. Patients were categorized into 2 groups: <3 months follow-up (n = 53) and ≥ 3 months follow-up (n = 57). We employed stepwise logistic regression, using intercostal MDR ≥ 25% in follow-up as an independent variable and age < 65 years, ventilator use, steroid use, follow-up > 3 months, hospital stay > 13 days, body mass index < 18.5 kg/m², and female gender as dependent variables. The loss of intercostal muscle was the most severe among the 3 chest wall muscles in the CT follow-up. Intercostal MDR was significantly higher in the ≥ 3 months follow-up group compared to the < 3 months group (32.5 ± 23.6% vs 19.0 ± 21.1%, P = .002). There were no significant differences in pectoralis MDR or T12 MDR between the 2 groups. Stepwise logistic regression identified steroid use (3.494 (1.419-8.604), P = .007) and a follow-up period > 3 months [3.006 (1.339-6.748), P = .008] as predictors of intercostal MDR ≥ 25%. The intercostal muscle wasting was profound compared to that in the pectoralis and T12 skeletal muscles in a follow-up CT scan, and the intercostal muscle wasting was further aggravated after 3 months of COVID-19 infection. The use of steroids and a follow-up period exceeding 3 months were significant predictors for ≥ 25% of intercostal muscle wasting in follow-up.