Author(s): SEGURA-JIMÉNEZ, V., TSIARLESTON, G., PAVÓN-MUÑOZ, R., BRYANT, A.L., DELGADO-FERNÁNDEZ, M., Institution: INSTITUTO DE INVESTIGACIÓN BIOSANITARIA IBS.GRANADA, Country: SPAIN, Abstract-ID: 1463

INTRODUCTION:
Beyond spinal pathology, the role of systemic muscle health in the persistence of chronic low back pain has gained significant attention [1]. This study aimed to examine (1) the cross-sectional association between sarcopenia severity and pain, and (2) the bidirectional prospective relationship between these constructs over a 2-year period in individuals with chronic primary low back pain (CPLBP).
METHODS:
A total of 171 individuals with CPLBP, recruited from a hospital setting in southern Spain at baseline (median age 51 [interquartile range 41, 58] years; 61.4% women), were followed over 2 years (n=59, median age 56 [IQR 48, 61] years; 54.2% women). A composite sarcopenia severity index was calculated by standardizing and aggregating measures of muscle mass (Skeletal Muscle Mass adjusted by Body Mass Index [SMM/BMI], measured via multi-frequency bioelectrical impedance analysis [InBody R20]) and strength performance (handgrip strength, chair-stand, Sørensen, and prone-bridging tests). To ensure that higher scores represented sarcopenia severity, z-scores for muscle mass and strength were inverted. Pain was evaluated using a multidimensional pain index, derived from standardized scores of: (1) pain intensity (0–10 Visual Analogue Scale [VAS]), (2) the bodily pain subscale of the self-reported Short Form-36 (SF-36) questionnaire, and (3) lumbar pressure pain thresholds (PPTs). Components where higher values reflect better health (SF-36 and PPTs) were inverted so that higher index scores represent greater multidimensional pain. Linear regression models were adjusted for age, sex, analgesic use (yes/no), and catastrophizing; longitudinal models were further adjusted for baseline values. No significant interaction between sex and the main predictors was found (all p > 0.39); therefore, all analyses were conducted using the total sample.
RESULTS:
Cross-sectional analysis revealed that a higher sarcopenia severity was significantly associated with greater multidimensional pain at baseline (β=0.258; p=0.016). Prospectively, baseline sarcopenia severity was a significant predictor of multidimensional pain at 2-year follow-up (β=0.596; p=0.004). Conversely, the inverse prospective model showed that baseline multidimensional pain did not predict changes in the sarcopenia severity over time (p=0.809), with sarcopenia severity showing high stability (Adj. R²=0.85).
CONCLUSION:
These findings suggest a unidirectional longitudinal relationship where sarcopenia severity predicts future multidimensional pain in CPLBP patients, rather than pain driving muscle deterioration. Clinical interventions focusing on maintaining muscle mass and strength may be crucial not only for physical function but also as a potential strategy to mitigate long-term multidimensional pain in this population.

[1]. Zhang Z, Guan Y, Xie S. Experimental Gerontology 2025; 210:112872.
[2]. Segura-Jiménez V, et al. Sports Health 2025; 17(2):342–350.

FUNDING: Instituto de Salud Carlos III (CP20/00178 and PI22/01791).