Risk factors and interaction effects in recurrent low back pain

To identify risk factors for low back pain (LBP) recurrence and develop a clinically applicable predictive model, with emphasis on interactions between key factors.

A retrospective cohort study was conducted, including 216 patients with newly-diagnosed LBP as the derivation cohort (January 2023-June 2024) and 46 as the external validation cohort (July-December 2024). Independent risk factors were screened through univariate, least absolute shrinkage and selection operator (Lasso), and multivariate logistic regression. Interaction effects were evaluated. A nomogram was constructed and validated.

The 1-month recurrence rate was 33.8%. Independent risk factors for recurrence included elevated white blood cell (WBC) count (OR=4.555, P<0.001), anxiety (OR=25.256, P<0.001), working >8 h/day (OR=8.748, P<0.001), and elevated interleukin-1β (IL-1β) (OR=3.356, P=0.008). Significant multiplicative interactions were observed between body mass index (BMI) and working hours, WBC and anxiety, and anxiety and working hours (all P<0.05). A positive additive interaction between WBC and anxiety was identified (RERI)=3.928). The nomogram demonstrated excellent discrimination (area under the receiver operating characteristic curve (AUC)=0.906 in the derivation cohort; 0.902 in the validation cohort), good calibration (Hosmer-Lemeshow P=0.06, 0.61), and optimal net benefit.

Elevated WBC, IL-1β, anxiety, and prolonged working hours predict LBP recurrence, with notable interactions among these factors. The proposed nomogram aids personalized risk stratification and informs work-related and psychological interventions.