Acupuncture for painful diabetic peripheral neuropathy: a systematic review and meta-analysis

Painful diabetic peripheral neuropathy (PDPN) is a common complication of diabetes that severely affects patients' quality of life, manifesting through symptoms such as numbness, burning, and tingling in the hands and feet. This systematic review and meta-analysis, published in Frontiers in Neurology in 2023, represents an important milestone in evaluating the efficacy of acupuncture for the treatment of PDPN. The investigators Zhou et al. conducted a comprehensive search across multiple databases, including PubMed, Embase, Web of Science, and Chinese databases, covering publications from inception through August 2023.

The study included 25 randomized controlled trials involving 1,561 patients with PDPN, all comparing different modalities of acupuncture combined with conventional treatment versus conventional treatment alone. The acupuncture modalities evaluated included traditional manual acupuncture, electroacupuncture, auricular acupuncture, acupoint injection, and moxibustion. The methodology rigorously followed the PRISMA guidelines, with two independent reviewers performing study selection and data extraction. Methodological quality was assessed using the Cochrane Risk of Bias 2 tool, and statistical analysis was conducted in RevMan 5.3.

The primary outcomes focused on pain intensity measured by the Visual Analog Scale (VAS) and the SF-36 Bodily Pain score. The results demonstrated consistent benefits of acupuncture across multiple measures. For the 16 studies that used the VAS (1,552 patients), a significant mean reduction of 1.62 points in pain intensity was observed when acupuncture was combined with conventional treatment, compared with conventional treatment alone. Particularly notable were the results from the submodalities: acupoint injection showed the greatest reduction (2.38 points), followed by moxibustion (2.50 points) and manual acupuncture (1.31 points).

For the 8 studies that used the SF-36, the standardized mean difference was 2.44, indicating substantial improvement in the perception of bodily pain. The analysis of secondary outcomes was also encouraging. The clinical efficacy rate was 39% higher in the acupuncture group, and the Toronto Clinical Scoring System (TCSS) showed a mean reduction of 1.47 points, suggesting improvement in overall neurological function. The subgroup analysis based on acupoint location revealed important insights for clinical practice.

The five most frequently used points were ST-36 (Zusanli), SP-6 (Sanyinjiao), LI-4 (Hegu), LI-11 (Quchi), and GB-34 (Yanglingquan), all located in the limbs. The analysis showed that both treatment focused on the limbs alone and treatment combining limbs and trunk were effective, but limb-only application had lower heterogeneity across studies. In terms of safety, only 2 of the 25 studies reported adverse events related to acupuncture, which were mild and reversible (local pain, discomfort, and swelling). This low incidence of adverse effects reinforces the favorable safety profile of acupuncture.

The proposed mechanisms for the efficacy of acupuncture in PDPN include modulation of oxidative stress through increased superoxide dismutase levels, reduced expression of advanced glycation end products, decreased glutamate levels in the central nervous system, and modulation of the inflammatory response through reduction of pro-inflammatory cytokines such as TNF-α and IFN-γ. Despite the promising results, the study has important limitations that should be considered when interpreting the results. Most of the trials were conducted in China, raising questions about generalizability to other populations. Adequate blinding was difficult to achieve due to the nature of the intervention, and there was high heterogeneity across studies due to differences in acupuncturist experience, needling techniques, point selection, and treatment duration.