Effectiveness of Acupuncture for Neck Pain: Systematic Review and Meta‑analysis with Trial Sequential Analysis

Neck pain is an extremely common condition affecting millions of people around the world, and is one of the leading causes of pain and disability. It is estimated that approximately 223 million people globally suffer from cervical pain, and approximately 22 million experience significant functional limitations due to this condition. The impact goes far beyond physical discomfort: between 30% and 50% of patients experience reduced work efficiency or even inability to work, generating a considerable socioeconomic burden. In the United States, spending on back and neck pain reached USD 134.5 billion in 2016, while in Belgium direct and indirect costs total approximately EUR 5 billion annually.

Conventional treatments for neck pain, such as nonsteroidal anti-inflammatory drugs and muscle relaxants, can provide temporary relief, but prolonged use frequently triggers adverse effects and shows limited efficacy in chronic cases. Current guidelines emphasize that the treatment of cervical pain should prioritize non-pharmacological therapies, using medications only as adjuncts and avoiding prolonged opioid use. In this context, acupuncture emerges as an important non-pharmacological therapeutic alternative, widely used in the treatment of various painful conditions. Although previous studies have suggested benefits of acupuncture for neck pain, the evidence remained inconclusive due to methodological limitations and the risk of exaggerated conclusions resulting from repeated significance testing.

To overcome these limitations, Chinese researchers conducted a comprehensive systematic review with meta-analysis and trial sequential analysis, an advanced statistical methodology that corrects type I errors and determines whether available evidence is sufficient for definitive conclusions. The study examined 26 randomized controlled trials involving 3,520 participants from twelve different countries, comparing acupuncture with inert treatments, manual therapy, and other active treatments. Most participants were female, with a mean age of 40.7 years, and presented with chronic cervical pain. The researchers evaluated several outcomes, including pain intensity, functional disability, pressure pain threshold, pain perception, quality of life, and adverse events.

The results demonstrated that acupuncture was significantly superior to inert treatments in multiple aspects. For pain intensity, acupuncture showed substantial reductions both immediately after treatment and at follow-up. Trial sequential analysis confirmed that these differences were not due to chance, with the cumulative sample size exceeding what was needed for statistically robust conclusions. Similarly, acupuncture demonstrated superiority in improving functional disability, significantly reducing limitations in patients' daily activities.

Pain perception also improved considerably with acupuncture, indicating not only a reduction in intensity but also in the subjective experience of discomfort. Regarding quality of life, patients treated with acupuncture showed significant improvements in physical functioning, general health, and mental component dimensions, suggesting benefits that transcend simple pain relief.

When compared with manual therapy, acupuncture showed advantages in pain reduction immediately after treatment and in improving pressure pain threshold. However, these advantages tended to diminish during the follow-up period, suggesting that the relative benefits may be more pronounced in the short term. Compared with other active treatments, such as anti-inflammatory drugs and usual care, acupuncture also demonstrated superior results, although the limited number of studies in these comparisons requires caution in interpretation. Regarding safety, acupuncture proved well tolerated, with an adverse event rate of only 6.4%, all of mild nature and with no serious reactions reported.

For patients and healthcare professionals, these findings have important clinical implications. Acupuncture can be considered a safe and effective therapeutic option for neck pain, particularly for patients who do not respond adequately to conventional treatments or who present medication intolerance. The results suggest that acupuncture can be integrated into existing treatment plans, potentially reducing the need for long-term pain medications. Cost-effectiveness studies cited by the authors indicate that acupuncture represents an economically viable strategy, either alone or in combination with conventional treatments.

The proposed mechanisms for the analgesic effects of acupuncture include the release of neurotransmitters and endogenous opioid-like substances, modulation of pain neural pathways, and regulation of complex brain networks involving the pain-inhibitory system.

However, the study presents important limitations that should be considered. The overall quality of evidence was classified as very low to moderate, with considerable heterogeneity between included studies. This variability may be related to differences in acupuncture protocols, treatment duration, point selection, and patient characteristics. Additionally, some of the observed effects may be partially attributable to nonspecific effects, such as patient expectations and placebo effects, making it challenging to distinguish the specific benefits of acupuncture.

The limited comparison with active treatments also restricts our understanding of how acupuncture compares with other established therapies.

The researchers acknowledge that more high-quality studies are needed to strengthen this evidence and better elucidate the underlying mechanisms. Particularly, there is a need for pragmatic trials evaluating the effectiveness of acupuncture in combination with other treatments, evidence-based standardized protocols, and studies addressing different subtypes of cervical pain. Despite these limitations, the trial sequential analysis provides robust evidence that the observed benefits are not due to statistical errors, offering greater confidence in conclusions about the efficacy of acupuncture for neck pain and guiding both clinical practice and future research in this area.