Effectiveness of Acupuncture for Katakori (Nonspecific Neck and Shoulder Stiffness/Tightness): A Systematic Review and Meta-Analysis

Katakori is a Japanese term that describes discomfort or dull pain associated with muscle stiffness around the back of the head, neck, and shoulders. This culturally specific condition significantly affects quality of life and work productivity in Japan, with a prevalence of 5.3% in men and 10.5% in women, making it the second most common musculoskeletal complaint after low back pain. Yoshimoto and colleagues estimated economic losses associated with presenteeism related to Katakori at approximately 27.9 billion dollars annually in Japan. This systematic review and meta-analysis was conducted following PRISMA 2020 guidelines to evaluate the effectiveness of acupuncture in the treatment of Katakori.

The researchers performed comprehensive searches in multiple databases, including PubMed, Cochrane CENTRAL, and Ichushi-Web, in addition to clinical trial registries and proprietary archives. Fourteen studies involving 831 participants were included in the review, with publications ranging from 1988 to 2024 and sample sizes from 15 to 400 participants. The mean patient age ranged from 20 to 60 years. The most frequently used acupuncture points were BL-10 (50% of studies), GB-21 (50%), and SI-14 (42.9%), all located on the trapezius muscle, corresponding to the areas where Katakori symptoms typically occur.

Acupuncture methods were categorized into manual acupuncture therapy and electroacupuncture. All studies used visual analog scales or numerical rating scales to measure the intensity of subjective symptoms. Risk-of-bias assessment using the Cochrane Risk of Bias 2 tool revealed that 46.4% of outcomes showed high risk of bias, 32.1% showed some concern, and only 21.4% showed low risk of bias. Information on allocation concealment was insufficient in most studies, and studies published before 2018 had not been prospectively registered as clinical trials.

The characteristics of included studies allowed four main comparisons: manual acupuncture versus sham acupuncture, acupuncture versus no treatment, acupuncture as adjuvant to usual care versus usual care, and press-tack needle versus sham press-tack needle. The meta-analysis revealed that manual acupuncture was not associated with significant improvements in subjective Katakori symptoms relative to sham acupuncture when considered overall. However, when sham controls were categorized into superficial penetration and non-penetrating subgroups, acupuncture proved more effective than non-penetrating sham acupuncture at the end of the treatment period, with a mean difference of -12.89 points. This finding suggests that penetrating acupuncture may be more effective than non-penetrating techniques, consistent with findings from previous analyses of acupuncture for chronic pain.

Only one study compared acupuncture with no treatment, demonstrating significant reduction in VAS scores immediately after the intervention. Similarly, only one study assessed acupuncture as an adjuvant to usual care, showing significant reduction in symptom intensity scores. The certainty of evidence was rated as very low due to high risk of bias and imprecision of results stemming from small sample sizes. The main reasons for downgrading the quality of evidence included risk of bias and imprecision, with total sample sizes much smaller than the 400 participants generally considered necessary for continuous variables.

Conceptual heterogeneity was also identified as an important issue, attributable to the diverse acupuncture stimulation methods and needling techniques used in the studies. Few randomized clinical trials used similar techniques to treat patients, which may result in a substantial gap in effectiveness in real-world clinical practice. Adverse events were reported in only six studies, all classified as minor, with no serious adverse events identified. However, it is important to note that the acupuncture points in the upper back and shoulder regions, frequently used for Katakori treatment, are associated with a high risk of pneumothorax.