The impact of obesity on the effectiveness of spinal cord stimulation in chronic spine-related pain patients.

BACKGROUND CONTEXT

Chronic pain and obesity are both on the rise. Spinal cord stimulation has gained increasing popularity in the pain management field for the treatment of spine-related chronic pain, however to-date, the correlation between the spinal cord stimulator effectiveness and increasing body mass index (BMI) has not been fully established.

PURPOSE

We aimed to investigate the correlation between patients' BMI and the percentage of pain relief as well as opioid utilization in chronic spine-related pain patients treated with spinal cord stimulation.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

Patients with chronic spine-related pain who were treated with a spinal cord stimulator.

OUTCOME MEASURES

Eleven-point numeric rating scale for pain and opioid utilization.

METHODS

Following Institutional Review Board approval, data from all eligible subjects who had undergone successful spinal cord stimulation (SCS)-trial defined as ≥50% decrease in pain followed by SCS implant were collected and statistically analyzed. Patients were divided into four groups according to BMI. Self-reported pain scores on the 11-point numerical rating scale were collected at baseline, 6 months and 12 months post SCS-implant visits. Opioid utilization, if any, was collected at baseline and 12 months post-SCS implant.

RESULTS

In all, 181 patients were included. Thirty-three were under and/or normal weight (≤24.9 kg/m), 72 overweight (25.0-29.9 kg/m), 63 obese (30.0-39.9 kg/m), and 13 morbidly obese (≥40.0 kg/m2). The estimated coefficients from multivariable linear regression analysis were -1.91% (95% CI: -2.82% to -0.991%) and -1.48% (95% CI: -2.30% to -0.660%) reduction in pain improvement per unit increase of BMI for 6 months and 12 months scores, respectively. The estimated coefficient of disability status was -15.3% (95% CI: -22.1% to -8.48%). The estimated coefficient for 12 month opioid equivalence was -0.08% (95% CI: -0.14 to -0.021), per` 1 mg unit increase of morphine opioid equivalency. The data showed a statistically significant negative association between increasing BMI and SCS effectiveness at 6 and 12 months post-SCS therapy with a 2% reduction in efficacy for every unit increase of BMI after adjusting for confounding factors and a 20% better response in underweight and/or normal patients over the morbidly obese individuals which was not related to baseline pain score level. The significant difference in pain scores at 6 months (p = .0003) and 12 months (p = .04) post-SCS implant between obese and nonobese patients was not attributable to differences in baseline pain scores. There was no significant change in opioid utilization between baseline and 12 months post-SCS therapy.

CONCLUSION

A negative association between SCS effectiveness and increasing BMI was found, whereas, no significant difference was noted amongst the various BMI cohorts and the daily opioid consumption.