AbstractBackground/Significance: Back pain affects about 80 percent of persons at some point in their lives. Lumbar intervertebral disc degeneration, lumbar stenosis and facet joint degeneration have been associated with low back pain. These degenerative changes increase with age. Genetic influences have been shown to affect the spinal degenerative process and the experience of pain. The symptoms that accompany degenerative spinal conditions include back pain, leg pain, numbness and weakness. Low back and leg pain are associated with reduced physical function. Physiological, situational and psychological patient characteristics have been shown to influence physical function in degenerative lumbar conditions. These characteristics include genotype, BMI, smoking, age, employment status, insurance type, worker's compensation claim and depression. Problem: Little is known about the interaction among patient characteristics and symptoms and the outcome of physical function for persons with degenerative lumbar spinal conditions. Purpose: This study was undertaken to explore the contribution of patient characteristics and symptoms to the outcome of physical function in a population of individuals experiencing lumbar degenerative conditions. Specific Aims: 1) Determine the contribution of physiological (BMI, sex, age, smoking status), situational (employment status, worker's compensation claim, insurance type), and psychological (depression) factors in persons receiving non-surgical interventions for degenerative lumbar conditions to symptoms and physical function, 2) Develop a predictive model for the outcome of physical function in persons receiving non-surgical interventions for lumbar degenerative conditions, using symptoms (back and/or leg pain, numbness, and weakness) and physiological, situational, and psychological patient factors, and 3) Explore the impact of the physiological factor genotype (disc structural genes and pain genes) on symptoms (back and/or leg pain, numbness, and weakness) and on physical function in persons experiencing lumbar degenerative conditions. Instruments: Physical function is the primary outcome, measured by the physical function subscale of the SF-36 and the Oswestry Disability Index, (ODI). Methods: Using a cross-sectional, observational design, 163 subjects were randomly selected from an existing database of completed SF-36 and ODI questionnaires at a tertiary outpatient spine center. Data on symptoms and physiological, situational, and psychological characteristics were obtained from the medical record. A random subset of 28 subjects with complete outcome measures and patient characteristics data consented to provide saliva samples for genotyping. Results: Aim 1: Smoking and having Medicaid insurance or no insurance were negatively associated with the symptom pain VAS. Higher BMI and smoking were associated with worse ODI scores, while having Commercial insurance or Medicare was associated with better ODI scores. Higher BMI, smoking, older age, and having Medicaid insurance were associated with worse SF-36 physical function subscale scores. Aim 2: Higher BMI, smoking, higher pain VAS and numbness predicted 35% of the variance in ODI scores. Higher BMI and older age and the symptom higher pain VAS predicted 26% of the variance in SF-36 physical function subscale scores. Aim 3: No genotype was significantly associated with symptoms. OPRM1 A/A carriers had significantly worse physical function scores than those with */G alleles. Implications: This study is an important step in identifying the combination of patient characteristics, (including genotype) and symptoms that impact physical function in this population, in order to tailor interventions to preserve physical function.
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