Age-referenced modeling of lumbar disc degeneration and its association with chronic low back pain: an MRI-based cross-sectional study.

BACKGROUND: Lumbar intervertebral disc degeneration is commonly found in patients with chronic low back pain (cLBP) but is also frequently observed in asymptomatic individuals. The lack of age-referenced values complicates the clinical interpretation of degenerative magnetic resonance imaging (MRI) findings. Using an age-dependent prediction model derived from a non-cLBP reference cohort, we estimated expected disc degeneration and examined whether degeneration exceeding age-expected levels is associated with cLBP status and pain intensity. METHODS: This cross-sectional analysis included 1,523 participants with complete lumbar Pfirrmann grading and clinical data (1,121 with cLBP; 402 without cLBP). Age-expected degeneration was modeled in the non-cLBP reference cohort using the Pfirrmann sum score from L1/2 to L5/S1. Standardized residuals were used to classify participants as below-expected, age-expected, or above-expected. Associations with cLBP and current pain intensity were assessed using multivariable regression adjusted for sex, body mass index (BMI), and smoking history; sensitivity models additionally adjusted for a cumulative score of Modic-classified vertebral bone marrow signal changes. RESULTS: Based on the non-cLBP reference cohort, a quadratic age-referenced reference model was established for the Pfirrmann sum score (L1/2-L5/S1):[Formula: see text] Above-expected lumbar Pfirrmann degeneration was associated with higher odds of cLBP compared with age-expected degeneration (odds ratio [OR] = 1.84; 95% confidence interval [CI], 1.36-2.50; p < 0.001) and compared with below-expected degeneration (OR = 4.13; 95% CI, 2.57-6.65; p < 0.001). After additional adjustment for the cumulative Modic score, the corresponding ORs were 1.66 (95% CI, 1.21-2.28; p = 0.002) and 3.63 (95% CI, 2.23-5.90; p < 0.001). CONCLUSION: This study provides an age-referenced framework for contextualizing lumbar Pfirrmann degeneration relative to expected values in individuals without cLBP. Above-age-expected multilevel disc degeneration was independently associated with cLBP status, supporting the clinical relevance of age-adjusted interpretation of conventional lumbar MRI degeneration grading.