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By Anne Cook, MD, FACP
Associate Program Director, AnMed Health Family Medicine Residency, Anderson, SC
Dr. Cook reports no financial relationships relevant to this field of study.
Synopsis:Yoga improved back pain and back-related function in minority and low-income subjects.
Source:Saper RB, et al. Comparing once- versus twice-weekly yoga classes for chronic low back pain in predominantly low income minorities: A randomized dosing trial. Evid Based Complement Alternat Med 2013;658030.
This randomized trial examined the use and frequency of yoga classes in a racially diverse and lower socioeconomic population for the treatment of chronic low back pain. The study enrolled 95 patients of lower socioeconomic status with chronic moderate-to-severe low back pain in a 12-week yoga trial comparing once-weekly classes with twice-weekly classes. There were, therefore, two parallel groups but no control group. Patients excluded from the study included those with known back pathologies (e.g., spinal canal stenosis, spondylolisthesis, ankylosing spondylitis, severe scoliosis, malignancy, and fracture), sciatica pain equal to or greater than low back pain, back surgery in the last 3 years, severe or progressive neurologic deficits, new back pain treatments started within the previous month or anticipated to begin during the study, pregnancy, yoga practice in the last 6 months, active or planned workers’ compensation, disability or personal injury claims, or perceived religious conflict. Yoga classes included 75 minutes of standardized yoga sessions as previously studied. All patients were also encouraged to participate in home practice as well and were given an audio CD and protocol. They were encouraged to participate in home practice 30 minutes per day. Patients were instructed to keep a log of time spent in practice.
The study revealed improvement in pain and back-related function in both groups, which is similar to findings in other studies. There have also been questions about how much yoga practice is needed for effectiveness. Once- and twice-weekly classes both showed clinically meaningful and statistically significant (P < 0.001) decreases from baseline in pain at 12 weeks: -2.1 (95% confidence interval [CI], -2.9 to -1.3) and -2.4 (95% CI, -3.1 to -1.8), respectively. Back-related function also improved for the once- and twice-weekly groups at 12 weeks: -5.1 (95% CI, -7.0 to -3.2) and -4.9 (95% CI, -6.5 to -3.3), respectively. The twice weekly group’s outcomes were not statistically different from the once weekly group.
Two questions were raised in the study. First, do patients of lower socioeconomic, more racially diverse status benefit from yoga similarly to their more affluent counterparts? Second, is there a "dosage" effect that would cause a greater benefit if patients attended two yoga classes per week instead of one class? Effectiveness previously shown had been criticized because prior study groups typically were disproportionably affluent and white and there were questions about the generalizability to other populations.
The answer to the question of effectiveness across populations appears to be yes. The outcomes from this study are similar to studies performed on more affluent and more highly educated populations with less racial diversity.1,2,3,4 For instance, the Sherman study compared 12 weekly yoga or exercise classes to a self-care book in patients with low back pain lasting longer than 12 weeks. In that study, back-related function in the yoga group was superior to the book and exercise groups at 12 weeks (yoga vs book: mean difference, -3.4 [95% CI, -5.1 to -1.6], P < 0.001; yoga vs exercise: mean difference, -1.8 [95% CI, -3.5 to -0.1], P = 0.034). At 26 weeks, back-related function in the yoga group was superior to the book group (mean difference, -3.6 [95% CI, -5.4 to -1.8]; P < 0.001). In that study, 97% of the participants had attended some college and 80% were white. Seventy-nine percent of those participants had an annual income > $35,000, and 87% were employed. In the Saper study, 65% did have some education beyond high school, 18% were white, and 22% had incomes > $40,000 (47% > $20,000). Forty-four percent were employed.5
The answer to the question of yoga "dosage" is a little less clear. On the surface, there was no significant difference between the two groups based on the assignment to once-weekly vs twice-weekly classes. However, the actual time spent in yoga practice (including class and home practice) as it was calculated showed very little difference between the two groups. Patients in the twice-weekly group were less likely to attend the classes and patients in the once-weekly group did more home practice. Overall, including home practice, the once-weekly group averaged 29 hours and the twice-weekly group averaged 37 hours — only a 28% difference in time spent. These calculations were, however, fraught with confounders. The adherence rate for participants in the once-weekly classes was 83% and in the twice-weekly classes was only 67%. Additionally, the calculation of home yoga time was not reliable. Only seven participants completed all 12 weeks of the diary of home practice. The researchers made some rather large assumptions to calculate the time spent in home yoga practice during weeks without recorded data. It was assumed to be the same as time spent during those weeks with recorded data. These assumptions really did compromise the vailidity of any data extrapolated to answer the question of dosing. Therefore, it would seem that this question is not reliably answered by this study.
It should be noted that the greatest benefit in back pain scores and back-related function occurred during the first 6 weeks of the study in both groups, prompting the authors to suggest that patients may benefit just as well from weekly classes for 6 weeks as they do for 12 weeks. A few other issues should be noted. There was no significant decrease in narcotic use in the population studied, although there was significant decrease in non-steroidal use. Despite the use of incentives for class attendance in the form of gift cards and and free classes, compliance was rather low in both the once-weekly classes and twice-weekly classes. Better adherence may well have provided for different results.
In short, this study of yoga therapy in a lower socioeconomic population, though fraught with some statistical concerns, seems to show benefit similar to that seen in other populations. Although more study is needed to confirm these preliminary findings, it would seem that practitioners who have yoga instruction easily available to their patients can feel comfortable in recommending yoga practice as one treatment for chronic low back pain. n