Yoga may lessen pain and improve function in patients with chronic, nonspecific low back pain, a new Cochrane review suggests.
However, it’s unclear whether yoga is more effective than other types of exercise, primarily because there’s so little evidence directly comparing these interventions, lead author L. Susan Wieland, assistant professor, Center for Integrative Medicine, University of Maryland School of Medicine, Baltimore, told Medscape Medical News.
“We think there doesn’t appear to be a difference in terms of back function and pain, but we are not really certain; we need more evidence.”
If yoga is more effective than a nonexercise intervention, and as effective as other exercise interventions, “the choice to use yoga may depend on availability, cost and participant or provider preference,” the investigators write.
The review was published January 12 in the Cochrane Database of Systematic Reviews.
The study included 12 randomized controlled trials from the United States, the United Kingdom, and India that enrolled a total of 1080 adult participants with chronic nonspecific low back pain.
According to the authors, low back pain, defined as pain or discomfort in the area between the lower rib and the gluteal folds, is a common and potentially disabling condition. The mean estimated lifetime prevalence ranges from 38.9% to 85%.
Low back pain is associated with loss of work productivity, poor quality of life, and high medical expenses. And it represents a substantial economic burden on society.
Back pain is sometimes associated with a particular cause (eg, radiculopathy or spinal stenosis), but most cases are of unknown origin and are classified as nonspecific. Low back pain may be acute (lasting less than 4 weeks), subacute (between 4 weeks and 3 months), or chronic (3 months or more).
The usual treatment for low back pain is self-care and nonprescription medications, such as acetaminophen or nonsteroidal anti-inflammatory drugs.
For chronic low back pain, the National Institute for Health and Care Excellence guidelines in the United Kingdom recommend exercise and some manual therapies in addition to nonprescription medication.
The mind-body practice of yoga has become very popular in the United States. According to the one national survey, in 2012 over 21 million US adults had used yoga during the previous year. Almost 20% said that their use of yoga was specifically for back pain.
Wide Range of Yoga Types
In most of the 12 included studies, the mean age was 42 to 48 years. Participants were recruited from clinical and/or community populations.
The studies compared yoga to a control intervention, such as a booklet on how to manage back pain or another type of exercise (eg, to strengthen abdomen or back muscles). The review also looked at studies of yoga as an adjunct to other therapies; for example, one small study compared back exercises and back exercises plus yoga.
The types of yoga varied between trials, but the most common was Iyengar, (a form of Hatha yoga) or a modification of this type of yoga. All interventions included meditation, relaxation, or breathing exercises, in addition to physical yoga poses.
For all but one small study, the yoga intervention consisted of one to three yoga classes per week, with each class lasting 45 to 90 minutes. That one small trial, carried out at a residential center, involved longer, intensive treatment for back pain (yoga vs occupational therapy).
In all studies, participants were encouraged to practice yoga at home.
Investigators assessed back-specific function by using the Roland-Morris Disability Questionnaire or another measure. They assessed pain by using various scales (such at the visual analogue scale).
Two studies did not report pain but rather the pain-related outcome of “symptom bothersome-ness.” The researchers transformed the pain data to a 0- to 100-point scale.
Nine trials examined yoga vs nonyoga exercise on back-related function. There was low-certainty evidence that yoga produced small to moderate improvements in back-related function at 3 to 4 months, corresponding to a change in the Roland-Morris Disability Questionnaire of a mean difference (MD) of –2.18 (95% confidence interval [CI], –3.60 to –0.76); moderate-certainty evidence for small to moderate improvements at 6 months, corresponding to a change in the Roland-Morris Disability Questionnaire of an MD –2.15 (95% CI, –3.23 to –1.08); and low-certainty evidence for small improvement at 12 months, corresponding to change in Roland-Morris Disability Questionnaire of an MD –1.36 (95% CI, –2.41 to –0.26).
On a 0- to 100-point scale, there was very low- to moderate-certainly evidence that yoga was slightly better for pain at 3 to 4 months (MD, –4.55; 95% CI, –7.04 to –2.06), 6 months (MD, –7.81; 95% CI, –13.37 to -2.25), and 12 months (MD, –5.40; 95% CI, –14.50 to –3.70).
However, this did not meet the predefined clinically significant change in pain of 15 points on the 0- to 100-point scale.
Four studies compared the effect of yoga with that of exercise. There was very low-certainty evidence showing little or no difference in back-related function at 3 months and 6 months and no information on back-related function after 6 months.
There was very low-certainty evidence for lower pain on a 0- to 100-point scale at 7 months and no information on pain at 3 months or after.
The analysis could not compare one style of yoga with another. “We were not able to say ‘these poses versus those poses are helpful.’ It seems like a wide range of yoga styles may be helpful,” said Dr Wieland.
She noted that the yoga classes were all designed for people with low back pain and were taught by experienced instructors, “so the aim was to be helpful, not harmful.” She agreed the findings may not be generalizable to typical group sessions offered at community centers.
Although there has been some suggestion that trials carried out in India show more beneficial effects of yoga, it was unclear from this new review whether this is the case, said Dr Wieland.
For example, the one study carried out at a residential center “is not really applicable to most settings in the US or elsewhere in the West,” she said. “It’s hard to untangle India versus not India.”
No Dose Relationship
There did not seem to be a “dose” relationship regarding the amount of yoga practiced. “We did not see any differences in effect estimates between the trials that we could clearly attribute to the number of classes,” said Dr Wieland. “The difference between one and two classes a week may not be very big.”
The authors were unable to conduct subgroup analyses that would have allowed them to compare older vs younger participants, higher socioeconomic status (SES) vs lower SES, and participants with and without major comorbidities.
“If we had additional research on these sorts of populations, we would have a better idea of the comparable benefits of yoga and nonyoga therapies, to help determine what types of people might be most suited to using yoga to manage back pain, said Dr. Wieland.
A “big unanswered question,” she said, is what aspect of yoga — the breathing, the stretching, or the meditation — most improves function and pain.
“Many people think that yoga could be better than other types of exercise because most yoga practices have this mind component — the breathing and the mental focus — but we don’t have enough evidence to say whether there really is a difference playing out in back function and pain when you compare it to other exercises.”
The studies generally provided only limited information on outcomes, such quality of life or depression.
There’s “virtually no evidence” looking at the impact of yoga on these “softer” outcomes, said Dr Wieland. “We definitely need more research looking at these sorts of things.”
Eight studies mentioned the presence or absence of adverse events, for example, a flare of back pain. The analysis found that the occurrence of adverse events was similar between yoga and other forms of exercise. No serious adverse events occurred in any of the studies.
This is consistent with previous research, said Dr Wieland.
Risk of Bias
The quality of the studies was affected by the risk of bias (yoga studies are difficult to blind).
“But even taking this into account, I think we can say that yoga is probably beneficial, with moderate certainty; the estimate of effect is really not bad,” commented Dr Wieland.
And while the issue of blinding “deserves further research,” the “bigger problem” is the lack of evidence for the comparison between yoga and other forms of exercise,” she said.
Research looking at longer-term outcomes is also needed, she added. “Most of this research only gave outcomes to 6 months; there is very little beyond that.”
Only one study was funded by a yoga institute.
“We downgraded the evidence from that study because we thought it could possibly be biased by their funding source,” said Dr Wieland.
The other studies were generally supported by government or nonprofit funding.
Commenting on the findings for Medscape Medical News, Jeffrey N. Katz, MD, professor of medicine and orthopedic surgery, and director, Scholars in Medicine Program, Harvard Medical School, Boston, Massachusetts, said the literature synthesis “was done quite rigorously by an outstanding group.”
The review findings, said Dr Katz, “suggest that for patients who are willing to invest the time and expense, yoga appears to be a safe means of achieving small improvements in function.”
Patients with chronic nonspecific back pain often ask their doctor about the value of yoga, said Dr Katz. “I think this review will help clinicians to counsel patients that the evidence we have suggests yoga is worth a try.”