Acupuncture-related adverse events: systematic review and meta-analyses of prospective clinical studies

Acupuncture is a millennia-old technique that has gained increasing popularity worldwide, offered by tens of thousands of physicians and health professionals. In Brazil, as in many other countries, it has become established as an important therapeutic option for various health conditions, especially chronic pain, headaches, postoperative nausea, and stress-related problems. Although there is solid scientific evidence regarding its efficacy for several medical conditions, questions about the safety of this practice still persist. It is essential that both patients and professionals have accurate information about the possible adverse effects of acupuncture in order to make informed decisions about its use.

This German study, published in BMJ Open in 2021, represents the first systematic review worldwide to mathematically calculate the risks of acupuncture-related adverse events. Researchers at the University of Munich systematically analyzed all available scientific literature through September 2019, looking for prospective studies that specifically evaluated the adverse effects of needle acupuncture. The methodology was rigorous, following international guidelines for systematic reviews and including only studies that followed patients over time. A total of 7,679 articles were initially identified, of which 22 met the established quality criteria, representing 21 independent studies that involved nearly 13 million acupuncture treatments.

Researchers categorized adverse events as mild or serious, with serious events being those that resulted in hospitalization, life-threatening conditions, or significant disability.

The results reveal a quite favorable safety profile for acupuncture. Out of every 100 patients who undergo a series of acupuncture sessions, approximately 9 may experience at least one mild adverse event. When considering individual treatments, approximately 8 of every 100 sessions may result in some adverse effect. It is important to note that half of these events are considered very mild and transient, such as minor bleeding at the needle site, transient pain, or redness around the insertion point.

Many specialists consider these effects as signs that the treatment is working properly, as they indicate the body is responding to the acupuncture stimulus. Serious adverse events are rare, occurring in approximately 1 in every 10,000 patients undergoing a series of treatments, or in roughly 8 cases per 1 million individual sessions. The most common serious events include pneumothorax (lung puncture), intense cardiovascular reactions that may cause fainting, and falls or trauma related to these reactions.

For patients, these results offer valuable information for treatment decision-making. Acupuncture can be considered one of the safest therapies in medicine, especially when compared to the adverse effects of medications commonly prescribed for chronic pain, such as anti-inflammatories and opioids. Patients should be aware that mild effects such as minor bleeding, transient pain, or fatigue after sessions are normal and generally indicate a positive response from the body. However, any prolonged discomfort or concerning symptoms should be immediately communicated to the practitioner.

For acupuncturists, the results emphasize the importance of solid medical training and proper instruction. Although serious events are rare, they require medical competence for adequate management and to minimize malpractice risks. The study highlights that most serious events can be avoided with appropriate training and correct technique.

The study presents some important limitations that should be considered. The main one is the considerable variability across the studies analyzed regarding the definition of what constitutes an acupuncture-related adverse event. Some studies included all events that occurred during treatment, regardless of their relationship to acupuncture, while others reported only events clearly caused by the procedure. In addition, there is ongoing debate in the scientific community about which local reactions should be considered adverse effects versus normal therapeutic responses.

The methodological quality of the studies also varied, with different forms of data collection and different definitions of severity. Another limitation is that many important studies published in Chinese were not included due to the language barrier, which may have influenced the results.

This work represents an important milestone in understanding the safety of acupuncture and provides essential data for evidence-based practice. The results confirm that acupuncture is among the safest treatments available in medicine, with very rare serious events and most adverse effects being mild and transient. To maximize safety, it is crucial that acupuncture be performed by properly trained professionals, especially considering the worldwide growth of this practice. The study also points to the need for international standardization in the definition and evaluation of adverse events in acupuncture studies, as well as clear criteria to distinguish adverse effects from desired therapeutic reactions.

Looking ahead, comparative studies that directly contrast the risks of acupuncture with those of conventional treatments for the same conditions will be important, further supporting informed clinical decision-making.