A systematic review of the effects of acupuncture on xerostomia and hyposalivation

This systematic review examined the efficacy of acupuncture in the treatment of xerostomia (the sensation of dry mouth) and hyposalivation (reduced saliva production), conditions that significantly affect patients' quality of life. Saliva plays fundamental roles in oral health, including lubrication, digestion, antimicrobial activity, and dental remineralization. When compromised, it can result in increased dental caries, gingivitis, fungal infections, and difficulties with speech and swallowing. The main causes of xerostomia include medication side effects (especially anticholinergics), radiation therapy for head and neck cancer, chemotherapy, and autoimmune diseases such as Sjögren syndrome.

The investigators conducted comprehensive searches of the PubMed and Web of Science databases through July 2015, initially identifying 341 potential articles. After rigorous application of inclusion and exclusion criteria, 10 randomized controlled studies were included in the analysis, involving 503 participants in total. The studies were categorized into three groups: five compared true acupuncture with sham/placebo acupuncture, four compared acupuncture with usual oral hygiene care, and one compared acupuncture with counseling sessions on oral care. The acupuncture protocols varied considerably across studies, including auricular acupuncture, traditional Chinese acupuncture, combinations of Chinese and Western medicine, and customized anatomical points.

The duration of treatments ranged from 4 to 10 weeks, with different session frequencies. The outcome measures included both objective parameters (unstimulated and stimulated salivary flow rate) and subjective measures (visual analog scales for dry mouth, xerostomia questionnaires, and quality-of-life questionnaires). The methodological quality assessment revealed significant limitations in all included studies. Using the Cochrane Collaboration risk-of-bias tool, all 10 studies were classified as having a high risk of bias in at least one domain.

The most common problems included failure to blind practitioners (present in all studies), inadequate allocation concealment, inconsistent acupuncture protocols, incomplete outcome data, and other sources of methodological bias. Only one study reported sample size calculations, suggesting that most lacked adequate statistical power to detect clinically significant differences. With regard to results, some studies suggested positive effects of acupuncture on both salivary flow and subjective dry-mouth symptoms. In studies comparing acupuncture with sham procedures, results were inconsistent.

Some showed improvements in unstimulated and stimulated salivary flow favoring acupuncture, but the differences often did not reach statistical significance. In studies comparing acupuncture with usual care, some reported significant differences favoring acupuncture, particularly in patients undergoing radiation therapy. Interestingly, the study that included exclusively patients with Sjögren syndrome found no significant effects of acupuncture. The clinical implications of this review are limited by the low quality of the available evidence.

Although acupuncture is generally considered a low-risk therapy, with significant adverse events being rare (fewer than 1 in 20,000 individuals), the lack of robust evidence calls into question its routine clinical application for xerostomia. The authors note that the estimated cost of a course of acupuncture treatment in the United States ranges from $400-600, which, combined with the limited evidence of efficacy, does not justify its widespread use outside of clinical research contexts. The limitations identified include the heterogeneity of acupuncture protocols, variability in the populations studied, different causes of xerostomia, varied oncological treatment modalities, and potentially inadequate washout periods in crossover studies. The authors conclude that, although some studies suggest potential benefits of acupuncture for xerostomia, particularly in post-radiation patients, the current evidence is insufficient to establish acupuncture as an evidence-based treatment for this condition.