Relationship between pectoralis muscle mass on chest CT and in-hospital death among patients with pneumonia

Background: Pneumonia severity index, which is calculated by combining multiple factors, is useful as prognostic indicators for pneumonia. However, simpler prognostic indicators have not been established. The concept of sarcopenia has been attracting attention in recent years, but its association with in-hospital mortality of patients with pneumonia is still unclear. Therefore, we investigated the relationship between pectoralis muscle mass on chest computed tomography (CT) and in-hospital mortality in patients with pneumonia. Methods: A retrospective cohort study was performed of patients aged 18 years or older with bacterial pneumonia, who underwent chest CT within 24 hours of admission between April 2014 and March 2019. We measured the thickness, area, and volume of the pectoralis major and minor muscles at the level of the aortic arch. Results: Of the 483 patients (mean age 77 ± 14 years, 300 men [62%]), there were 51 in-hospital deaths (11%). In univariate analysis, decreased thickness, area, and volume of the pectoralis major and minor muscles were significantly associated with increased in-hospital mortality. Multivariate analysis with adjustment for age, gender, serum albumin, A-DROP, revealed that thinner pectoralis major and minor muscles were independent factors of poor prognosis (odds ratio 0.878, 95% confidence interval (CI) 0.783–0.985, P = 0.026 / odds ratio 0.842, 95% CI 0.733–0.968, P = 0.016). Approximately 25% of the patients died when the pectoralis minor muscle thickness was 5 mm or less, and no patients died when it was 15 mm or more. Conclusions: The pectoralis muscle mass may be an independent prognostic factor in hospitalized patients with pneumonia.