Effects of Molecular Hydrogen Inhalation on Primary Dysmenorrhea: A Single-Group Time-Series Pilot Study
Yuko Yurugi; Iori Arisue; Carlos Egydio de Carvalho; Katsuya Watanabe; Masahito Watanabe · Japanese Journal of Complementary and Alternative Medicine. 2026;23(1):1-8.
Study at a glance
Thirteen women recorded menstrual symptoms before, during and after one cycle of hydrogen inhalation. Average pain scores were lower during the intervention cycle and rose again afterward. Without a placebo or another control group, the study cannot show whether hydrogen caused the change.
Human
13 women with primary dysmenorrhea; mean age 22.2 ± 4.2 years. Study period July 2022–December 2025.
Seated nasal-cannula hydrogen for 15 minutes per session, three times weekly from the end of menstruation to the end of the next menstrual cycle. · Device-output purity 99.995%; actual inspired H₂ concentration not measured/reported.
One intervention menstrual cycle within a three-cycle before/during/after observation.
Pain VAS (100 mm), mean ± SD: 66.5 ± 14.1 before, 34.6 ± 18.7 during and 57.7 ± 23.0 after the intervention cycle. Before versus during P < 0.001; during versus after P = 0.030; before versus after P = 0.230. These are within-person time comparisons, not a controlled treatment effect. Composite score medians were 4.0, 2.0 and 4.0; the source defines it as a sum despite a multiplication-style label.
Thirteen women, no concurrent or placebo control and subjective outcomes. Ordinary menstrual-cycle variation, expectations and regression to the mean cannot be separated from an intervention effect. Several exploratory comparisons were not adjusted for multiplicity. Proposed mechanisms were not established by measured biomarkers. Generator purity is not the inspired concentration.
What kind of evidence is this?
Human
Uncontrolled single-group time-series pilot with three menstrual-cycle observations: before, during, and after hydrogen exposure. No randomization, no blinded placebo comparator.
原発性月経困難症に対する水素吸入の効果：単一群時系列パイロット研究
Published 31 August 2026; released on J-STAGE 10 September 2026. Main full text English; Japanese abstract and alternate title retained.
Women’s health
Inhaled H₂
Information not yet classified
Some editorial classification fields are still pending. The source-reported outcomes and result are shown below; Hydrogenology does not infer a positive or negative signal from prose automatically.
Methods
13 women with primary dysmenorrhea; mean age 22.2 ± 4.2 years. Study period July 2022–December 2025.
13 enrolled and analyzed; no randomization or concurrent control group.
One intervention menstrual cycle within a three-cycle before/during/after observation.
Seated nasal-cannula hydrogen for 15 minutes per session, three times weekly from the end of menstruation to the end of the next menstrual cycle.
Hydrogen gas from a generator; 99.995% is device-output purity, not inspired concentration.
Device-output purity 99.995%; actual inspired H₂ concentration not measured/reported.
Reported generator flow 300 cc/min ± 5%; not patient uptake.
No supplemental oxygen co-delivery described.
The participants' preceding and subsequent menstrual cycles without the intervention; no concurrent control group.
Outcomes and reported result
Dysmenorrhea severity, analgesic-use frequency, composite score and pain VAS; no prospective primary-outcome hierarchy specified.
Pain VAS (100 mm), mean ± SD: 66.5 ± 14.1 before, 34.6 ± 18.7 during and 57.7 ± 23.0 after the intervention cycle. Before versus during P < 0.001; during versus after P = 0.030; before versus after P = 0.230. These are within-person time comparisons, not a controlled treatment effect. Composite score medians were 4.0, 2.0 and 4.0; the source defines it as a sum despite a multiplication-style label.
The available main full text was reviewed for methods, results, limitations and declarations. Remaining source-specific uncertainties are stated in this record.
No adverse events observed in this 13-person pilot; no long-term safety conclusion is supported.
A reported association, difference or mechanism is not automatically a clinical benefit.
Limitations and applicability
Thirteen women, no concurrent or placebo control and subjective outcomes. Ordinary menstrual-cycle variation, expectations and regression to the mean cannot be separated from an intervention effect. Several exploratory comparisons were not adjusted for multiplicity. Proposed mechanisms were not established by measured biomarkers. Generator purity is not the inspired concentration.
13 women with primary dysmenorrhea; mean age 22.2 ± 4.2 years. Study period July 2022–December 2025. Findings apply only to the studied design and exposure; no treatment or device recommendation.
None declared (p6).
None declared (p6).
No single-study GRADE certainty rating is assigned. Read how records and evidence assessments are prepared.
Sources and record status
Source ID: doi-10.1625-jcam.23.1 · DOI: 10.1625/jcam.23.1
Complete publisher article on J-STAGE: main text in English, with a Japanese abstract.
AI-assisted editorial review of the available main full text, 29 October 2026. The source version and access limitations are stated in this record. No independent clinical or statistical assessment has been performed.
Full PDF pp 1-8: Methods and ethics pp 2-3; Results pp 3-4; Tables 1-3 (Table 2/3 visually inspected on p 4); Discussion/limitations pp 4-6; funding/conflicts p 6; Japanese abstract p 8.
AI-assisted editorial review of the available main full text, 29 October 2026. Complete publisher article on J-STAGE: main text in English, with a Japanese abstract.
Trial registration not reported. Hakuho College ethics approval Hakurinken 22001; written informed consent reported.
29 October 2026
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