Efficacy of acupuncture for tension-type headache prophylaxis: systematic review and meta-analysis with trial sequential analysis

This systematic meta-analysis with trial sequential analysis (TSA) represents the most robust evaluation conducted to date on the efficacy of acupuncture for the prevention of tension-type headache (TTH). The investigators analyzed 14 randomized controlled trials involving 2,795 participants from ten different countries, using standardized diagnostic criteria from the International Headache Society. Tension-type headache is one of the most prevalent neurologic conditions globally, affecting 26.1% of the world population and causing 7.2 million years lived with disability in 2016. Characterized by mild to moderate intensity pain with a sensation of tightness, constriction, or pressure around the head, TTH has a female predominance and significantly impacts quality of life, work productivity, and learning capacity.

The study included adults with episodic or chronic TTH, comparing true acupuncture with sham acupuncture (placebo), no treatment, or other active therapies such as physical training and relaxation. The primary outcome was headache frequency (number of days with pain), while secondary outcomes included response rate (≥50% reduction in frequency) and adverse events. The analysis was conducted at two time points: at the end of treatment and during the follow-up period. When compared with sham acupuncture, true acupuncture demonstrated significant superiority in reducing headache frequency both at the end of treatment (SMD -0.80; 95% CI -1.36 to -0.24; p=0.005) and at follow-up (SMD -1.33; 95% CI -2.18 to -0.49; p=0.002).

The quality of evidence was considered low due to heterogeneity among studies. Compared with no treatment, acupuncture showed significant benefit at the end of treatment (SMD -0.52; 95% CI -0.63 to -0.41; p<0.001), with TSA confirming sufficient sample size. Regarding response rate, acupuncture demonstrated superiority over placebo both post-treatment (RR 1.28; 95% CI 1.12 to 1.46; p=0.0003) and at follow-up (RR 1.37; 95% CI 1.19 to 1.58; p<0.0001), with moderate-quality evidence. The TSA at follow-up reached the required information size, strengthening the reliability of the results.

Regarding safety, there was no significant difference in adverse event rates between true and sham acupuncture (RR 1.14; 95% CI 0.67 to 1.94; p=0.62). Reported events included dizziness, hematoma, pain, and severe headache, with no serious adverse events reported. Subgroup analyses revealed that electroacupuncture, dry needling, and laser acupuncture may be more effective than manual acupuncture. For chronic TTH specifically, there was no significant difference at the end of treatment, but acupuncture was superior at follow-up.

The main innovation of this study was the use of TSA, which controls for statistical errors resulting from repeated significance testing in cumulative meta-analyses. This method calculates the required information size and establishes sequential monitoring boundaries, determining whether additional studies are needed. The TSA results confirmed sufficient statistical power for some comparisons but indicated the need for more studies for others. The clinical implications are substantial.

Acupuncture emerges as a valid therapeutic option for TTH prevention, with efficacy maintained after treatment and a favorable safety profile. This is particularly relevant considering that pharmacologic treatments may cause adverse effects and that non-pharmacologic therapies are increasingly valued. Limitations include heterogeneity among studies, possible publication bias, and absence of direct comparisons with standardized medications for TTH. In addition, different acupuncture protocols and study populations may influence the generalizability of results.

Future studies should focus on comparisons with established medications, investigation of different acupuncture modalities, and long-term follow-up to determine the durability of benefits.