MUSCLE MASS & COVID OUTCOMES EXAMINED IN 2 STUDIES

Recent publications from 2 locations in Germany used different techniques to look at muscle mass and outcomes in SARS-Co-V2 patients during the height of the pandemic. Both found associations between loss of muscle mass and mortality. Both were published in the Journal of Cachexia, Sarcopenia and Muscle.

In the first study, Kremer et al¹ assessed muscle quantity by sonographic muscle indices as possible predictors of COVID-19 outcome. This team first examined a cohort of patients without COVID-19 to obtain median reference values for low muscle quantity by gender—using the psoas muscle area index (PMAI) as well as the thigh muscle thickness index (TMTI). Then the group looked at 2 cohorts of patients—Cohort I from the initial round of the pandemic, and Cohort II from the second wave.

The PMAI showed the most favorable characteristics to predict COVID-19 disease outcome, when compared to other muscle indices. Using sonographic morphometry in the cohort without COVID-19, gender-specific medians for PMAI (male: 291.1 mm²/m², female 260.6 mm²/m²) were identified as threshold values of low muscle quantity. Among the COVID-19 patients, 22.4% of Cohort I (13/58) and 34.5% of Cohort II (20/55) developed a critical course of disease. The mortality rate reached 12.1% in Cohort I (7/58) and 20% in Cohort II (11/55) within 30 days of follow-up. COVID-19 patients with a PMAI below the gender-specific median showed a higher 30-day mortality in both COVID-19 cohorts (log rank, P < 0.05). The optimal PMAI cutoff value (206 mm²/m²) predicted 30-day mortality of hospitalized COVID-19 patients with a sensitivity of 72% and specificity of 78.5% (receiver operating characteristic-area under the curve: 0.793, 95% confidence interval 0.671–0.914, P = 0.008). Multivariable log-regression analysis of PMAI, age, gender, body mass index, and comorbidities confirmed an independent association of low PMAI with 30-day mortality of COVID-19 patients (P = 0.018).

The authors concluded that sonographic morphometry can provide reliable muscle quantification under hygienic precautions and allows risk stratification of patients with COVID-19.

In the second publication—a systematic review and meta-analysis, Meyer et al² found significant effect for low skeletal muscle mass (LSMM) and visceral fat areas (VAT) on mortality and unfavorable outcomes in COVID-19 patients, using both univariate as well as multivariate analyses. Their review examined 6 studies to understand the association between LSMM and VATs and in-hospital mortality in COVID-19 patients using computed tomography (CT). The studies in the review included 1,059 patients (591 men, 55%) with a mean age of 60.1 years (range, 48–66).

The pooled prevalence of LSMM was 33.6%. The pooled odds ratio for the effect of LSMM on in-hospital mortality in univariate analysis was 5.84 [95% confidence interval (CI), 1.07–31.83]. It was 2.73 (95% CI, 0.54–13.70) in multivariate analysis. The pooled odds ratio of high visceral fat area on unfavorable outcome in univariate analysis was 2.65 (95% CI, 1.57–4.47).

These authors concluded that CT-defined LSMM and high VATs have a relevant effect on unfavorable outcomes and in-hospital mortality for COVID-19 patients and call for the inclusion of these measures as prognostic biomarkers in the clinical routine for these patients. They also note that body composition is an emergent field of research not just related to COVID-19. Given that all patients in critical care are at risk of muscle wasting, as are the elderly with primary sarcopenia, the authors argue that the ease of calculating LSMM and VAT from existing CT images calls for further research into these parameters.