Differential factors associated with muscle quantity and quality in older adults

Abstract

Introduction

Sarcopenia involves a progressive decline in skeletal muscle mass and strength. Appendicular skeletal muscle mass (ASMM) is a traditional diagnostic marker, while phase angle (PhA) has emerged as an indicator of cellular integrity and physiological resilience. This study aims to identify factors associated with muscle quantity (ASMM) and muscle quality (PhA) in older adults.

Materials and methods

A multicenter cross-sectional analysis was conducted using two cohorts from Ireland and Spain. Assessments included ASMM and PhA via bioelectrical impedance analysis (BIA), rectus femoris (RF) thickness through ultrasound, and handgrip strength (HGS) via dynamometry. Two crosswise multivariable linear regression models explored independent predictors of ASMM and PhA.

Results

Seventy-four participants were included (83.8% women; mean age 78.7 years [SD 8.67]). Sarcopenia prevalence was 27% by HGS and 50% by ASMM. Polypharmacy was associated with lower PhA (4.57° [SD 0.79], p = 0.021), reduced RF thickness (1.05 cm [SD 0.38], p < 0.001), and weaker HGS (19 kg [SD 10.2], p = 0.020). The ASMM model (adjusted R² = 0.725) identified sex, body mass index (BMI), HGS, comorbidity burden and PhA as significant predictors. The PhA model (adjusted R² = 0.440) showed age, comorbidity burden, RF thickness, HGS, and ASMM as independent determinants.

Conclusions

RF thickness was independently associated with PhA, suggesting it reflects muscle quality and cellular integrity beyond ASMM. ASMM depends mainly on anthropometric characteristics. Although interrelated, PhA and ASMM capture distinct domains, supporting the complementary role of ultrasound in geriatric musculoskeletal and nutritional assessment.

Resumen

Introducción

La sarcopenia implica la pérdida progresiva de masa y fuerza muscular. La Masa Muscular Esquelética Apendicular (ASMM) es un marcador diagnóstico tradicional, mientras que el Ángulo de Fase (PhA) es un indicador de integridad celular y resiliencia fisiológica. El objetivo es identificar factores asociados a la cantidad (ASMM) y calidad (PhA) muscular.

Materiales y métodos

Análisis transversal multicéntrico con dos cohortes (Irlanda y España), que determinó ASMM y PhA mediante bioimpedancia eléctrica (BIA), grosor del recto femoral (RF) por ecografía y fuerza de prensión manual (HGS). Se realizaron modelos de regresión lineal multivariable cruzados para identificar predictores de ASMM y PhA.

Resultados

74 participantes (83,8% mujeres, edad media de 78,7 años [SD 8.67]). La prevalencia de sarcopenia fue 27% por HGS y 50% por ASMM. La polifarmacia se asoció con menor PhA (4.57° [SD 0.79], p = 0.021), grosor del RF (1.05 cm [SD 0.38], p < 0.001) y HGS (19 kg [SD 10.2], p = 0.020). El modelo de ASMM (R² ajustado = 0,725) identificó al sexo, IMC, HGS, carga de comorbilidad y PhA como predictores significativos. El modelo PhA (R² ajustado = 0,440) mostró la edad, carga de comorbilidad, grosor del RF, HGS y ASMM como determinantes independientes.

Conclusiones

El grosor del RF se asoció de manera independientemente con el PhA, reflejando la calidad muscular e integridad celular, a diferencia del ASMM que depende principalmente de características antropométricas. Aunque PhA y ASMM están interrelacionados, abarcan distintos dominios, respaldando la ecografía como método complementario en la valoración musculoesquelética-nutricional geriátrica.