# Inhalation of hydrogen gas elevates urinary 8-hydroxy-2'-deoxyguanine in Parkinson's disease.
> パーキンソン病患者における水素ガス吸入と尿中8-OHdG上昇：ランダム化二重盲検クロスオーバー試験


## Abstract

A randomized, double-blind, placebo-controlled crossover trial with an 8-week washout period enrolled 20 Parkinson's disease (PD) patients who inhaled approximately 1.2–1.4% hydrogen gas for 10 minutes twice daily over 4 weeks. Olfactory function, non-motor symptoms, activities of daily living, and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) were assessed. No statistically significant changes in clinical PD parameters were detected; however, urinary 8-OHdG concentrations rose by approximately 16%. This magnitude of increase is substantially smaller than the over 300% elevation seen in diabetes and is more comparable to levels observed following intense physical exercise. The authors propose that hydrogen-induced oxidative stress markers may reflect hormetic cellular adaptation, potentially involving Nrf2 and NF-κB pathway activation and heat shock responses, suggesting that beneficial effects of hydrogen could be mediated partly through such mechanisms.

### Mechanism

Hydrogen inhalation may activate the Nrf2 and NF-κB signaling pathways along with heat shock responses, inducing cytoprotective cellular adaptations through a hormetic mechanism, as reflected by a modest elevation in urinary 8-OHdG.

## Bibliographic

- **Authors**: Hirayama M, Ito M, Minato T, Yoritaka A, LeBaron TW, Ohno K
- **Journal**: Med Gas Res
- **Year**: 2018
- **PMID**: [30713666](https://pubmed.ncbi.nlm.nih.gov/30713666/)
- **DOI**: [10.4103/2045-9912.248264](https://doi.org/10.4103/2045-9912.248264)
- **PMC**: [PMC6352570](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6352570/)
- **Study type**: human randomized controlled trial
- **Delivery route**: inhalation
- **Effect reported**: null
- **H2 concentration**: 1.2–1.4%

## Delivery context

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

## Safety notes

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [LFL / UFL terminology](https://h2-papers.org/en/safety-notes/lfl-ufl-explained)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

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> **Cite as**: H2 Papers — PMID 30713666. https://h2-papers.org/en/papers/30713666
> **Source**: PubMed PMID [30713666](https://pubmed.ncbi.nlm.nih.gov/30713666/)