Sex- and age-stratified analysis of structural risk factors for disabling chronic low back pain in a Japanese longitudinal cohort.

PURPOSE: Disabling chronic low back pain (DCLBP) imposes a growing burden in aging societies. Although lumbar disc degeneration (DD), vertebral fractures (VF), and lumbar spinal stenosis (LSS) are known contributors, their differential impact across age and sex remains unclear. This study aimed to identify age- and sex-specific structural risk factors for DCLBP in a Japanese community-based cohort.

METHODS

We included 653 participants (219 male, 434 female; mean age 62.1 ± 13.0 years) from the Wakayama Spine Study. Baseline assessments included MRI-based DD scores, radiographic VF scores at T11-L1, and LSS severity. DCLBP at follow-up was defined as low back pain ≥ 3 months with an Oswestry Disability Index ≥ 21%. Multivariable logistic regression was conducted stratified by age (40-64, 65-74, ≥ 75) and sex. Interaction terms were included to evaluate effect modification.

RESULTS

DCLBP was identified in 13.9% of participants, and its prevalence increased with age (9.6% in the 40-64 years group; 13.8% in the 65-74 years group; and 20.4% in the 75 years and older group). In the 40-64 years group, higher body mass index (BMI) was independently associated with DCLBP (odds ratio [OR]: 1.13; 95% confidence interval [CI]: 1.01-1.26; p = 0.033). Among participants 75 years or older, the vertebral fracture (VF) score was a strong predictor of DCLBP, particularly for female participants (OR: 1.82; 95% CI: 1.27-2.59; p = 0.001). Overall, the VF score (OR: 1.45; 95% CI: 1.16-1.81; p = 0.001) and lumbar disc degeneration score (OR: 1.19; 95% CI: 1.01-1.39; p = 0.036) of female participants were significantly associated with DCLBP. Interaction analyses revealed significant modification effects (age × VF score: p = 0.018; sex × DCLBP: p = 0.041) that suggested that the disability burden of structural spinal degeneration is particularly pronounced in older women.

CONCLUSION

Risk profiles for disabling chronic low back pain vary significantly by age and sex. Higher BMI is a key modifiable risk factor for younger adults, whereas vertebral fractures and disc degeneration are major contributors in older women. Age- and sex-tailored strategies, such as weight management during midlife and proactive fracture prevention in older women, are necessary to reduce the disability burden.