Multivariable analyses of the relationships between age, gender, and body mass index and the source of chronic low back pain.

OBJECTIVE To examine the combined relationships between age, gender, and body mass index (BMI) and the specific source of chronic low back pain. DESIGN Retrospective chart review. SETTING University spine center. PATIENTS Charts from 378 cases from 358 consecutive patients were reviewed and 157 independent cases from 153 patients who underwent definitive diagnostic injections were analyzed. INTERVENTIONS Discography, dual diagnostic facet joint blocks, sacroiliac joint injections, anesthetic interspinous ligaments/opposing spinous processes/posterior fusion hardware injections, percutaneous augmentation. OUTCOME MEASURES Chronic low back pain source was the primary outcome variable. Predictor variables included age at initial presentation, gender, and BMI. RESULTS Age, gender, and BMI were each significantly associated with the source of chronic low back pain, after controlling for the effects of each other. Increases in age were associated with significant decreases in the odds of internal disc disruption (IDD) vs facet joint pain (FJP), sacroiliac joint pain (SIJP), and other sources and decreases in the odds of FJP and SIJP vs other sources. Being female was associated with significant increases in the odds of SIJP vs IDD, FJP, and other sources. Increased BMI was associated with significant increases in the odds of FJP vs SIJP. CONCLUSIONS These findings suggest a significant relationship among gender, age, and BMI and structural causes of chronic low back pain. Lumbar IDD is more prevalent in young males while FJP is more prevalent in females with increased BMI. Female gender and low BMI are associated with SIJP.