The persistence of the effects of acupuncture after a course of treatment: A meta-analysis of patients with chronic pain

One of the major challenges in chronic pain treatment has been understanding not only whether a treatment is effective, but how long its benefits last after therapy ends. For patients who have lived with pain for years or even decades, the question of the durability of therapeutic effects is fundamental. In the case of acupuncture, although previous studies have demonstrated its efficacy for various chronic painful conditions, an important uncertainty remained about the persistence of these benefits over time. This question has significant practical implications both for patients considering undergoing treatment and for healthcare professionals making referrals, in addition to directly impacting economic analyses of the therapy's cost-effectiveness.

To clarify this crucial question, researchers from the Acupuncture Trialists' Collaboration conducted a comprehensive meta-analysis using individual patient data from 29 high-quality randomized controlled clinical trials. The study included 17,922 patients with chronic pain conditions, encompassing musculoskeletal pain such as low back pain, neck and shoulder pain, knee osteoarthritis, and headaches or migraines. The methodology employed was particularly robust, as it directly analyzed how pain scores changed over time after treatment ended, rather than simply comparing results at isolated time points. The researchers used sophisticated statistical techniques that accounted for the correlation between repeated measurements from the same patient over time, providing a more accurate analysis of the trajectory of acupuncture effects.

The main results revealed a quite encouraging picture for the persistence of acupuncture benefits. When acupuncture was compared with non-acupuncture controls (such as waiting list or usual care), the researchers observed that the effects diminished only in a non-significant manner, with a reduction of 0.011 standard deviation every three months after the end of treatment. This means that approximately 90% of the benefits of acupuncture relative to controls were maintained at 12-month follow-up. For studies comparing true acupuncture with sham acupuncture (placebo), there was a slightly larger reduction in effects over time, of 0.025 standard deviation every three months, suggesting that about 50% of the benefits would persist at 12 months.

Interestingly, when researchers excluded the specific neck pain studies from the analysis, the results for acupuncture versus placebo improved considerably, with approximately 70% of benefits being maintained over one year.

These findings have important and reassuring clinical implications for patients and professionals. Patients considering acupuncture for chronic pain can be reassured that the benefits obtained during treatment do not disappear quickly after its end. This is particularly relevant given that many of the included studies involved patients with chronic pain lasting decades. For healthcare professionals, these results offer solid evidence that acupuncture represents a lasting therapeutic investment, not just temporary relief.

In addition, the findings have substantial economic implications, since many cost-effectiveness analyses of acupuncture previously assumed that benefits ceased immediately after the last study follow-up. Based on this evidence, using a 12-month time horizon instead of 3 months in economic analyses would reduce the cost per quality-adjusted life year by 75%, making acupuncture an even more economically attractive option.

The study has some important limitations that should be considered when interpreting the results. Not all included clinical trials provided follow-up data at multiple time points after treatment, and only eight of the twenty studies followed patients for 40 weeks or more. Only one study offered a two-year follow-up after randomization. In addition, significant heterogeneity was observed between studies, particularly evident in the neck pain trials, where the effects of acupuncture diminished more rapidly compared with other conditions.

This may be related to the fact that treatments for neck pain tended to be shorter (3-4 weeks) compared with other conditions (6-8 weeks or longer). Despite these limitations, the researchers consider it reasonable to conclude about the persistence of acupuncture effects over a 12-month period, based on the consistency of available data and the absence of significant differences between studies with longer versus shorter follow-up. It is important to note, however, that although we can conclude about the persistence of effects up to 12 months, it is not possible to extrapolate these findings to longer periods without additional specific studies.