# Muscle Radiodensity Reduction in COVID-19 Survivors Is Independent of NLR Levels During Acute Infection Phase

## TL;DR

This study found that muscle quality declines in COVID-19 survivors, regardless of their inflammation levels during hospitalization.

## Contribution

The study shows that muscle radiodensity reduction in COVID-19 survivors is independent of NLR levels during acute infection.

## Key findings

- Both low and high NLR groups showed reduced skeletal muscle radiodensity and increased intramuscular fat.
- No changes were observed in subcutaneous or visceral adipose tissue between hospitalization and follow-up.
- Age and intramuscular fat infiltration during hospitalization were linked to reduced muscle radiodensity.

## Abstract

COVID-19 survivors often experience late symptoms, possibly secondary to an exacerbated inflammatory response. This study aimed to investigate whether inflammatory levels, assessed by the neutrophil-to-lymphocyte ratio (NLR) during hospitalization in the acute phase of SARS-CoV-2 infection, affect the skeletal muscle phenotype and adipose tissue of COVID-19 survivors during outpatient follow-up after discharge. This retrospective, single-center study included COVID-19 survivors hospitalized from March 2020 to April 2021, who attended outpatient follow-ups 3 to 9 months after discharge. Patients were divided into two groups based on inflammatory levels during hospitalization: (1) low NLR (≤4.2) and (2) high NLR (>4.2). The skeletal muscle phenotype and adipose tissue were assessed using computed tomography. The study included 60 patients: 20 low NLR and 40 high NLR. The high NLR group was unexpectedly younger, but had longer hospital stays and required more intensive care. We observed a reduction in skeletal muscle radiodensity and an increase in skeletal muscle fat in both groups. However, we observed no differences in subcutaneous and visceral adipose tissue between hospitalization and follow-up. We conclude that COVID-19 survivors show reduced skeletal muscle radiodensity and increased skeletal muscle fat infiltration post-hospitalization, regardless of NLR levels during acute infection. In addition, age and intramuscular fat infiltration during hospitalization are associated with reducing skeletal muscle radiodensity. This highlights the need for targeted rehabilitation to address long-term muscle effects and recovery.