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Researchers found that lower lean muscle mass and higher intermuscular adipose tissue acted as imaging-visible markers that stratify risk for chronic back pain.

Lower lean muscle mass (LMM) and higher intermuscular adipose tissue (InterMAT) are independently associated with risk for chronic back pain (CBP), CBP symptom burden, and musculoskeletal comorbidities, according to a study published online in The Lancet Regional Health Europe.

“Prior research showed inconsistent findings regarding the role of muscle composition in CBP, limited by small sample sizes, reliance on non-imaging or X-ray imaging techniques, and region-specific muscle assessments,” wrote corresponding study author Keno Bressem, MD, of the Technical University of Munich, and study coauthors. “Critically, our results support the interdependent relationship between LMM and InterMAT and demonstrate the relevance of muscle composition within the context of musculoskeletal comorbidities, specifically OA [osteoarthritis] and OP [osteoporosis].”

Nationwide Co-Hort Study

The researchers analyzed whole-body magnetic resonance imaging (MRI) data from 27,518 adults enrolled in the German National Cohort (median age 49 years; 44% women). Among them, 21.8% reported CBP, defined as back pain persisting for more than 3 months.

A validated deep-learning model quantified LMM and InterMAT; mixed logistic regression adjusted for demographic, metabolic, and musculoskeletal confounders.

Muscle Composition, Physical Activity, & Comorbidities

The authors discovered that each 2-unit Z-score rise in InterMAT increased the odds of CBP by 22% (odds ratio [OR] 1.22, 95% confidence interval [CI] 1.13–1.30), whereas a comparable rise in LMM lowered those odds by 13 % (OR 0.87, 95% CI 0.79–0.95). The study team noted similar directions for high symptom burden: InterMAT OR 1.17 and LMM OR 0.63.

Participants with low (<500 metabolic equivalent task [MET] min/week) or very high (>5000 MET min/week) physical activity levels had a higher prevalence of CBP (24.6% and 22.0%, respectively) compared with those with moderate (500–5000 MET min/week) physical activity levels (19.4%), according to the study.

Stratified analyses showed the InterMAT–LMM pattern persisted in OA and OP. Higher pain intensity (numeric rating scale ≥4) increased the odds of higher InterMAT and lowered the odds of LMM, independent of physical activity levels or skeletal comorbidities.

“Notably,” the researchers added, “our findings revealed significant differences in muscle composition among participants with these comorbidities, who demonstrated significantly higher InterMAT and lower LMM values. These observations suggest that muscle composition may extend beyond being a specific parameter for CBP to serve as a holistic indicator of musculoskeletal health.”

The Role of MRI in Chronic Back Pain

According to the authors, lower LMM and higher InterMAT emerged as modifiable, imaging-visible markers that stratify risk for CBP and CBP symptom severity, even when conventional spinal findings are absent.

“The role of imaging in CBP is a subject of ongoing debate, primarily due to the lack of association between degenerative changes of the spine and CBP as well as pain symptomatology. However, paraspinal muscle composition, often overlooked in routine diagnostics, may serve as a noninvasive biomarker for CBP,” the authors concluded, adding, “Future research should focus on longitudinal designs to explore causal pathways and underlying biological mechanisms.”