The aim of this commentary was to discuss in a rehabilitation perspective the published Cochrane Review “Physical Activity and Exercise for Chronic Pain in Adults: An Overview of Cochrane Reviews” by Geneen et al.1 (https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD011279.pub3/full), which was developed by the Cochrane Pain, Palliative and Supportive Care Group. This Cochrane Corner is produced in agreement with the American Journal of Physical Medicine & Rehabilitation by Cochrane Rehabilitation.
Chronic pain is defined by the International Association for the Study of Pain as pain lasting beyond normal tissue healing time, ie, longer than 12 wks.2 Global burden of chronic pain is tremendous; 8 of the top 12 disabling noncommunicable diseases worldwide—ie, low back pain, neck pain, migraine, arthritis, other musculoskeletal conditions, depression, anxiety, and drug use disorder—are all either conditions causing chronic pain or psychological disorders that are strongly associated with chronic pain.3 When treating chronic pain, physicians traditionally give preference to pharmacological interventions. However, nonpharmacological interventions, such as physical activity, may be helpful for alleviating chronic pain. The objective of this overview of Cochrane Reviews was to determine whether, in adults with chronic pain, different types of physical activity and exercise interventions may reduce pain severity and have an impact on function, quality of life, and healthcare use. In addition, the authors analyzed whether there was any harm associated with these interventions.1
PHYSICAL ACTIVITY AND EXERCISE FOR CHRONIC PAIN IN ADULTS: AN OVERVIEW OF COCHRANE REVIEWS
What Is the Aim of the Cochrane Review?
The aim of this overview of Cochrane Reviews was to analyze the benefits and harms of physical activity and exercise as an intervention in adults with chronic pain. Outcomes included pain severity, function, quality of life, and use of healthcare resources.
What Was Studied in the Cochrane Review?
The population analyzed in this study was adults 18 yrs or older, experiencing chronic noncancer pain caused by rheumatoid arthritis, osteoarthritis, fibromyalgia, low back pain, intermittent claudication, dysmenorrhea, mechanical neck disorder, spinal cord injury, postpolio syndrome, and patellofemoral pain for at least 3 mos (12 wks) in any body site. The intervention under evaluation was physical activity or exercise as a stand-alone treatment (aerobic, strength, flexibility, range of motion, and core or balance training programs, as well as yoga, Pilates, and tai chi). Eligible comparators were usual care, waiting list control, placebo/sham treatment, or a combination of treatments. The primary outcome was the severity of self-reported pain. The secondary outcomes were physical function, psychological function, quality of life, adherence to the prescribed intervention, healthcare use/attendance, adverse events, and death.
What Were the Main Results of the Cochrane Review?
The overview included 21 previous Cochrane Reviews with 381 studies and a total of 37,143 participants. These reviews were published before March 21, 2016. A total of 264 studies (19,642 participants) examined exercise versus no exercise in adults with chronic pain and were used in the analysis. Because of the limited data available, the evidence was reported qualitatively.
The results of the overview are as follows:
Self-reported pain severity: There were 15 reviews that reported a mean or usual pain score for exercise (intervention) and control groups. None of the included reviews fulfilled the requirements for first-tier evidence, defined as at least 50% pain reduction from baseline, study duration longer than 8 wks, and more than 200 participants per arm. Ten reviews reported some benefit of exercise on pain severity; only three of these reviews did not find statistically significant changes in usual or mean pain from any intervention. However, results across interventions and follow-up were inconsistent, because exercise did not consistently result in either positive or negative change in self-reported pain scores at any single point.
Physical function (objectively or subjectively measured): Physical function was reported as the primary outcome measure in 8 of 21 reviews; 14 reviews showed that the intervention resulted in a statistically significant benefit compared with the control. However, even these statistically significant results had only small to moderate effect sizes. Large effect sizes were reported by only one review, but the evidence included in that review was judged as being low to very low quality by the original review authors.
Psychological function: In 5 of 21 reviews, psychological function was assessed as mental health, anxiety, and depression. Results were variable, with conflicting data regarding the benefits of the intervention on psychological function (both positive results and “no effect”). Negative effects were not reported.
Quality of life: Nine reviews assessed the impact of the intervention using different quality-of-life assessment tools. Results were variable, with some reviews showing positive effect, and some showing no difference between groups. Negative effects were not reported.
Adherence to the prescribed intervention: Only one review reported adherence to the intervention, but results could not be evaluated because of poor reporting in most of the studies. There was no significant difference in risk of withdrawal/dropout between exercising group and control.
Healthcare use/attendance: This outcome was not reported in any review.
Adverse events, potential harm, and death: Eighteen of 21 reviews reported data for adverse events. Most of the adverse events were increased soreness or muscle pain, which reportedly subsided within a few weeks of the intervention. Only one review reported death separately; based on the available evidence, the intervention was protective against death, but this result did not reach statistical significance.
What Were the Authors' Conclusions?
The authors concluded that the quality of the evidence examining physical activity and exercise for adults with chronic pain is low, which is largely due to small sample sizes and potentially underpowered studies. There is some evidence of benefit on pain severity and improved physical function after an exercise intervention in this patient population although the effect sizes were small to moderate. The effect on quality of life was variable. Available evidence supports that none of the analyzed interventions caused harm to the participants. Of note, evidence was only available for people with mild to moderate pain (moderate is greater than 3/10 or 30/100 on a pain scale), with only one review reporting on studies that addressed moderate to severe pain (severe pain is greater than 6/10 or 60/100). Therefore, it is unclear whether this evidence is applicable to patients with severe chronic pain.
What Are the Implications of the Cochrane Evidence for Rehabilitation?
The Cochrane Review1 summarized in this Cochrane Corner Rehabilitation addresses a wide range of physical activity and exercise interventions to improve pain intensity, physical function, and quality of life in adults with chronic pain.
The rehabilitation implications are that physical activity and exercise may reduce pain intensity and improve physical function in adults with chronic pain, although the effect sizes are small to moderate and the quality of the evidence is low. None of the interventions assessed seemed to cause harm to the participants.
We suggest that rehabilitation professionals continue to offer physical activity and exercise (aerobic, strength, flexibility, range of motion, and core or balance training programs, as well as yoga, Pilates, and tai chi) for improving pain, physical function and quality of life in adults with chronic pain.
We thank Cochrane Rehabilitation and Cochrane Pain, Palliative and Supportive Care Group for reviewing the contents of the Cochrane Corner.