Evaluation of the effectiveness and efficacy of Iyengar yoga therapy on chronic low back pain

Abstract

Study design: The effectiveness and efficacy of Iyengar yoga for chronic low back pain (CLBP) were assessed with intention-to-treat and per-protocol analysis. Ninety subjects were randomized to a yoga (n = 43) or control group (n = 47) receiving standard medical care. Participants were followed 6 months after completion of the intervention.

Objective: This study aimed to evaluate Iyengar yoga therapy on chronic low back pain. Yoga subjects were hypothesized to report greater reductions in functional disability, pain intensity, depression, and pain medication usage than controls.

Summary of background data: CLBP is a musculoskeletal disorder with public health and economic impact. Pilot studies of yoga and back pain have reported significant changes in clinically important outcomes.

Methods: Subjects were recruited through self-referral and health professional referrals according to explicit inclusion/exclusion criteria. Yoga subjects participated in 24 weeks of biweekly yoga classes designed for CLBP. Outcomes were assessed at 12 (midway), 24 (immediately after), and 48 weeks (6-month follow-up) after the start of the intervention using the Oswestry Disability Questionnaire, a Visual Analog Scale, the Beck Depression Inventory, and a pain medication-usage questionnaire.

Results: Using intention-to-treat analysis with repeated measures ANOVA (group x time), significantly greater reductions in functional disability and pain intensity were observed in the yoga group when compared to the control group at 24 weeks. A significantly greater proportion of yoga subjects also reported clinical improvements at both 12 and 24 weeks. In addition, depression was significantly lower in yoga subjects. Furthermore, while a reduction in pain medication occurred, this was comparable in both groups. When results were analyzed using per-protocol analysis, improvements were observed for all outcomes in the yoga group, including agreater trend for reduced pain medication usage. Although slightly less than at 24 weeks, the yoga group had statistically significant reductions in functional disability, pain intensity, and depression compared to standard medical care 6-months postintervention.

Conclusion: Yoga improves functional disability, pain intensity, and depression in adults with CLBP. There was also a clinically important trend for the yoga group to reduce their pain medication usage compared to the control group.

Figure 1. Participant flow through the randomized trial

Figure 2. Changes in functional disability among yoga and control group participants

The mean functional disability score (% total on ODI) and standard error of the mean is depicted. The Oswestry Disability Index (ODI) is scored from 0–10 with higher scores indicating greater functional disability. The score is expressed as a percentage of the total possible score. Statistically significant p values from follow-up linear contrasts at 12 and 24 weeks to the repeated measures ANOVA test are indicated as follows: * p<.0125, ** p <.01, *** p < .001.

Figure 3. Changes in pain intensity among yoga and control group participants

The mean pain intensity score (mm on VAS) and standard error of the mean is depicted. The Visual Analog Scale (VAS) is scored from 0–100 with higher scores indicating more severe pain. Statistically significant p values (p < .001) from follow-up linear contrasts at 12 and 24 weeks to the repeated measures ANOVA are indicated by the asterisk (*).

Figure 4. Changes in depression among yoga and control group participants

The mean depression score (BDI-II) and standard error of the mean is depicted. The Beck Depression Inventory (BDI-II) is scored from 0–63 with higher scores indicating greater depression. Statistically significant p values from follow-up linear contrasts at 12 and 24 weeks to the repeated measures ANOVA test are indicated as follows: * p <.01, ** p < .001.

Figure 5. Clinically relevant changes in functional disability among yoga and control group participants

Mean percent of the total participants who reported a clinically important improvement (6 point change) in functional disability is depicted. Fritz and Irrgang {Fritz, 2001} used an external criterion of patient’s perception of global rating of change to determine that a 6-point difference between groups on the ODI was a minimum clinically important difference. Statistically significant p values from follow-up linear contrasts at 12 and 24 weeks to the repeated measures ANOVA test are indicated as follows: * p<.05, ** p <.01, *** p <.001.

Figure 6. Clinically relevant changes in pain intensity among yoga and control group participants

Mean percent of the total participants who reported a clinically important improvement (18.5 mm change) in pain intensity is depicted. Hägg et al. {Hägg, 2003} using the external criterion of patient global assessment of treatment effect, determined that 18–19 units on a 100 millimeter VAS was a minimally clinically important difference. Statistically significant p values from follow-up linear contrasts at 12 and 24 weeks to the repeated measures ANOVA test are indicated as follows: * p<.05, ** p <.01, *** p <.001.

Figure 7. Successful change in pain medication usage among yoga and control group participants

Mean successful changes from baseline in low back pain (LBP) medication usage are depicted. Only those who reported taking medications at baseline for LBP are included. Changes in a subject’s pain medication usage were coded as: (1) failure, i.e., no change or increase in dosage, frequency, and/or amount or (2) success, i.e., decrease in dose, frequency, and/or amount or cessation of medication. Decreasing the dose or stopping of one or more components of a multiple-drug regimen was considered a successful alteration in drug usage. While not statistically significant, a trend toward higher success rates in decreasing pain medication was apparent for the yoga as opposed to the control group at both time points.