Acupuncture for Chronic Pain: Individual Patient Data Meta-analysis

Acupuncture is one of the most popular complementary therapies in the world, especially for the treatment of chronic pain, a condition that affects millions of people globally. Although widely used — approximately 3 million Americans receive acupuncture treatment annually — its effectiveness has been the subject of intense controversy in the medical community. Originally derived from Chinese medicine, acupuncture involves the insertion of fine needles at specific points on the body. Despite studies demonstrating that the technique produces physiological effects relevant to pain relief, there is not yet a fully accepted biological mechanism to explain its lasting effects on chronic pain.

This lack of clear scientific explanation, combined with its origins in traditional theories, makes acupuncture a highly controversial treatment in Western medicine.

This study represents the most comprehensive and rigorous analysis ever conducted on the efficacy of acupuncture for chronic pain. The investigators established extremely strict quality criteria, including only randomized controlled trials where the randomization process was unequivocally determined to be adequate. From the more than 900 publications initially identified, only 31 studies met the established quality criteria. The authors were able to obtain individual patient data from 29 of these studies, totaling 17,922 participants from countries such as the United States, the United Kingdom, Germany, Spain, and Sweden.

The study analyzed four main chronic pain conditions: back and neck pain, osteoarthritis, chronic headache, and shoulder pain. The investigators compared acupuncture with both sham acupuncture (in which needles are inserted superficially or do not penetrate the skin) and with no-acupuncture control groups. This methodology of individual patient data meta-analysis is considered superior to traditional analyses because it allows greater statistical precision and better data quality.

The results clearly and significantly demonstrated that acupuncture is superior both to sham treatment and to no treatment for all the pain conditions studied. To illustrate practically: on a 0-100 pain scale, where a typical patient might start with a score of 60, follow-up scores would be approximately 43 in the no-acupuncture group, 35 in the sham acupuncture group, and 30 in patients who received true acupuncture. The effects were consistent across different types of pain, with effect sizes of 0.23 to 0.37 standard deviations when compared with sham acupuncture and 0.42 to 0.57 when compared with no treatment. In terms of clinical response, defined as a 50% or greater reduction in pain, the rates would be approximately 30% with no acupuncture, 42.5% with sham acupuncture, and 50% with true acupuncture.

Importantly, these results remained robust even after several sensitivity analyses, including those related to potential publication bias.

For patients suffering from chronic pain, these findings represent solid evidence that acupuncture can be an effective and clinically relevant treatment option. The difference between true and sham acupuncture, although smaller than the difference between acupuncture and no treatment, indicates that there is a specific effect of needles beyond placebo effects. For healthcare professionals, the results suggest that acupuncture should be considered a reasonable referral option for patients with chronic pain. The magnitude of the effects observed is clinically significant and comparable to other accepted treatments for chronic pain.

The study also demonstrates that the total effects of acupuncture, as experienced by patients in routine clinical practice, are relevant and include both specific effects of correct needle insertion and nonspecific effects related to the therapeutic context and patient expectations.

The study acknowledges some important limitations that should be considered in interpreting the results. Comparisons between acupuncture and no-treatment controls cannot be blinded, which may introduce performance and response bias. Although the investigators considered the risk of bias in studies with sham acupuncture to be low, the professionals applying the treatment obviously knew which procedure they were performing, and some influence on the results cannot be completely ruled out. Another consideration is that the study combined different types of outcome measures and different follow-up periods, although sensitivity analyses showed that this did not materially affect the results.

The investigators also observed limited evidence of publication bias, but calculated that 47 unpublished studies showing an advantage for sham acupuncture would be needed for the difference to lose statistical significance. In conclusion, this study provides the most robust evidence available that acupuncture represents a reasonable therapeutic option for patients with chronic pain, offering benefits beyond placebo effects, even though the latter also contribute to its total therapeutic effect.