Molecular Hydrogen (Inhaled)

Inhaled molecular hydrogen (usually a hydrogen and oxygen gas mixture) has a scattered human randomized trial base, one small trial per indication. Zheng et al. (Respiratory Research, 2021; PMID 33985501): multicenter double-blind trial in acute exacerbation of COPD, hydrogen and oxygen against oxygen alone; the Breathlessness, Cough and Sputum Scale, a self-reported symptom score, fell 5.3 against 2.4 points at day 7, with lung function and blood gases unchanged; the comparator was oxygen alone and the trial was registered after it began. Tao et al. (Journal of Cellular and Molecular Medicine, 2022; PMID 35734974): 43 subjects with NAFLD, 13 weeks; liver fat on imaging improved in moderate to severe cases, a surrogate. Gao et al. (Medical Gas Research, 2026; PMID 40826930): 66 people with sleep disorders, single-blind, 7 days; sleep time, efficiency and questionnaire scores improved; funded by the device company Jinkai Instrument (Dalian), which took part in data analysis, interpretation and writing. Shi et al. (J Clin Biochem Nutr, 2023; PMID 37970554): 64 patients with Omicron COVID-19, shorter viral shedding, one small trial. Ono et al. (J Stroke Cerebrovasc Dis, 2017; PMID 28669654): 50 patients with acute cerebral infarction, 3 percent hydrogen twice daily for 7 days against conventional intravenous medication, not placebo and not blinded; stroke scale and imaging improved. Tamura et al. (EClinicalMedicine, 2023; PMID 36969346), HYBRID II: 15-hospital double-blind placebo-controlled trial of 2 percent hydrogen for 18 hours after out-of-hospital cardiac arrest, stopped early at 73 patients; the primary outcome, good neurological function at 90 days, was 56 against 39 percent and not significant (relative risk 0.72, 95% CI 0.46 to 1.13, p=0.15); 90-day survival and the modified Rankin scale favored hydrogen as secondary outcomes; funded by the gas supplier Taiyo Nippon Sanso. Ohsawa et al. (Nature Medicine, 2007; PMID 17486089): cell culture and a rat ischemia model, the selective-antioxidant mechanism; preclinical, no weight for a human grade. Lin et al. (J Pers Med, 2023; PMID 36675728): 184 adults aged 65 and over having noncardiac surgery; delirium in 12 against 24 percent. Wu et al. (2024; PMID 39099781): single-center trial after glioma surgery; smaller brain edema volume on imaging. Yoritaka et al. (Neurol Sci, 2021; PMID 34319514): 20-person double-blind Parkinson's pilot, no difference on the MDS-UPDRS. Chen et al. (2026; PMID 41908285): 53 infants with epileptic spasms, no difference in spasm relief, more adverse findings with hydrogen. Grade C: single unreplicated small positives per indication, and the one hard-endpoint trial missed its primary outcome. Inhaled hydrogen is graded separately from hydrogen water (also C), a different delivery, dose and evidence base.