Inhalation of hydrogen gas elevates urinary 8-hydroxy-2′-deoxyguanine in Parkinson’s disease
Hirayama M, Ito M, Minato T, Yoritaka A, LeBaron TW, Ohno K. · Medical Gas Research. 2018;8(4):144–149.
Study at a glance
Human
People with Parkinson's disease receiving stable levodopa treatment.
Nasal inhalation for 10 minutes twice daily for four weeks, followed by crossover after an eight-week washout. · The generator supplied 3.0–3.5% H₂ in mixed air at 2 L/min. The authors estimated that dilution by a 5 L/min minute ventilation produced approximately 1.2–1.4% inspired H₂.
10 minutes twice daily for four weeks per condition, with an eight-week washout.
H₂ produced no significant effect on odor identification, UPDRS part I or UPDRS part II. Urinary 8-OHdG increased by 16% after H₂ (paired p=0.02), but order-stratified subgroups were not significant by ANOVA. The authors proposed hormesis as a hypothesis; the trial did not demonstrate a beneficial clinical effect.
Only 20 participants, short low-dose exposure, several endpoints and a biomarker increase whose proposed hormetic meaning remains unproven. Funding included Japanese ministries and AMED, the Hori Sciences and Arts Foundation and the Smoking Research Foundation; authors declared no conflicts.
What kind of evidence is this?
Human
Randomized double-blind placebo-controlled crossover trial
Parkinson’s disease
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
People with Parkinson's disease receiving stable levodopa treatment.
20 patients: 8 men and 12 women; mean age 69±6.8 years. Ten received H₂ first and ten placebo first.
10 minutes twice daily for four weeks per condition, with an eight-week washout.
Nasal inhalation for 10 minutes twice daily for four weeks, followed by crossover after an eight-week washout.
H₂ diluted in room air — H₂ as the experimental component, not Brown's gas.
The generator supplied 3.0–3.5% H₂ in mixed air at 2 L/min. The authors estimated that dilution by a 5 L/min minute ventilation produced approximately 1.2–1.4% inspired H₂.
Approximately 60–70 mL/min H₂, calculated from 3.0–3.5% of the reported 2,000 mL/min generator output.
Mixed room air was the carrier and placebo. No separate O₂ intervention was used; O₂ percentage and absolute O₂ flow in the device output were not reported.
Placebo device delivering 2 L/min air through an identical nasal cannula.
Outcomes and reported result
Japanese odor identification, UPDRS parts I and II and urinary 8-hydroxy-2′-deoxyguanine normalized to creatinine.
H₂ produced no significant effect on odor identification, UPDRS part I or UPDRS part II. Urinary 8-OHdG increased by 16% after H₂ (paired p=0.02), but order-stratified subgroups were not significant by ANOVA. The authors proposed hormesis as a hypothesis; the trial did not demonstrate a beneficial clinical effect.
The complete PMC article, crossover sequence, device output, inspired-concentration estimate, all clinical outcomes, oxidative marker analysis, funding and conflict declaration were checked; null clinical results are prominent.
A reported association, difference or mechanism is not automatically a clinical benefit.
Limitations and applicability
Only 20 participants, short low-dose exposure, several endpoints and a biomarker increase whose proposed hormetic meaning remains unproven. Funding included Japanese ministries and AMED, the Hori Sciences and Arts Foundation and the Smoking Research Foundation; authors declared no conflicts.
People with Parkinson's disease on stable levodopa under this short crossover protocol; it did not show improvement in the measured clinical features.
No single-study GRADE certainty rating is assigned. Read how records and evidence assessments are prepared.
Sources and record status
PMID: 30713666 · DOI: 10.4103/2045-9912.248264
Free full article on PubMed Central.
PubMed metadata and complete PubMed Central article; full-text and article-status check completed 8 August 2026.
10 August 2026
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