2022 · Liu et al. — The Effect of a Low Dose Hydrogen-Oxygen Mixture Inhalation in Midlife/Older Adults with Hypertension: A Randomized, Placebo-Controlled Trial
Super-Abstract
In adults aged 50 to 70 with hypertension, inhaling a hydrogen-oxygen mixture (66% hydrogen) 4 hours a day for 2 weeks lowered arm systolic blood pressure compared with baseline, from 151.9 to 147.1 mmHg on the right arm, while blood pressure did not change with placebo air. Night-time diastolic ambulatory pressure fell by 2.7 mmHg, and angiotensin II, aldosterone and cortisol were lower than at baseline in the hydrogen group. All reported effects are changes within each group: the abstract gives no direct statistical comparison between the two groups, so it does not show that hydrogen lowered blood pressure more than placebo air. (Frontiers in Pharmacology, 2022.)
Commentary
The study asked whether inhaling a low-dose hydrogen-oxygen mixture affects blood pressure in midlife and older adults with hypertension. It randomised 60 participants aged 50 to 70 to placebo air or a mixture of 66% hydrogen and 33% oxygen, each inhaled 4 hours a day for 2 weeks. The abstract does not say whether participants or staff were blinded, does not give the gas flow rate and does not name a primary endpoint. Blood pressure at all four limbs and 24-hour ambulatory blood pressure were measured before and after the intervention, together with plasma hormones related to hypertension. In total, 56 participants completed the study: 27 in the air group and 29 in the hydrogen-oxygen group. A subgroup analysis compared participants aged 50 to 59 with those aged 60 to 70.
Key quotes
- „The right and left arm systolic blood pressure (SBP) were significantly decreased in H2-O2 group compared with the baseline levels (151.9 ± 12.7 mmHg to 147.1 ± 12.0 mmHg, and 150.7 ± 13.3 mmHg to 145.7 ± 13.0 mmHg, respectively“ — the main result, a change from baseline within the hydrogen group
- „No significant differences were observed in the Air group before and after the intervention.“ — the placebo result, again compared only with its own baseline
- „Inhalation of a low-dose H2-O2 mixture exerts a favorable effect on blood pressure, and reduces the plasma levels of hormones associated with hypertension on renin-angiotensin-aldosterone system and stress in midlife/older adults with hypertension.“ — the authors' conclusion, based on before-and-after comparisons within groups
Our assessment
The trial was randomised and used placebo air as a comparator. The abstract reports only before-and-after changes within each group, not a direct comparison between hydrogen and placebo, so it cannot show that the hydrogen mixture lowered blood pressure more than air. The authors' conclusion of a favourable effect rests on these within-group comparisons. Limitations: 60 participants and 2 weeks of treatment. Blinding and a primary endpoint are not mentioned in the abstract. Many blood pressure readings and hormones were analysed, which raises the risk of false-positive findings. The age comparison splits an already small sample. Blood pressure and hormone levels are surrogate markers, and cardiovascular events were not studied. Adverse events and the flow rate of the gas are not reported in the abstract.
Study design
- Type: randomised, placebo-controlled trial (blinding not stated in the abstract), 2 weeks · n: 60 randomised, 56 completed (27 air, 29 H₂-O₂) · H₂ delivery: inhaled hydrogen-oxygen mixture (66% H₂, 33% O₂), 4 hours a day for 2 weeks
- Comparator: inhaled placebo air on the same schedule
- Result: no primary endpoint named; all tests within groups against baseline. H₂-O₂ group: right arm SBP 151.9 to 147.1 mmHg, left arm 150.7 to 145.7 mmHg (all p < 0.05), night-time diastolic ambulatory BP −2.7 ± 6.5 mmHg (p < 0.05), angiotensin II, aldosterone, cortisol and aldosterone-to-renin ratio lower (p < 0.05). Air group: no significant changes. Larger right arm SBP fall at age 60 to 70 than at 50 to 59 (p < 0.05)
Abstract
Objective: To explore the effect of a low-dose hydrogen-oxygen (H2-O2) mixture inhalation in midlife/older adults with hypertension. Methods: This randomized, placebo-controlled trial included 60 participants with hypertension aged 50-70 years who were randomly divided into Air group (inhaled placebo air) or H2-O2 group [inhaled H2-O2 mixture (66% H2/33% O2)]. Participants in both groups were treated 4 h per day for 2 weeks. Four-limb blood pressure and 24-h ambulatory blood pressure were monitored before and after the intervention, and levels of plasma hormones related to hypertension were determined. Results: A total of 56 patients completed the study (27 in the Air group and 29 in the H2-O2 group). The right and left arm systolic blood pressure (SBP) were significantly decreased in H2-O2 group compared with the baseline levels (151.9 ± 12.7 mmHg to 147.1 ± 12.0 mmHg, and 150.7 ± 13.3 mmHg to 145.7 ± 13.0 mmHg, respectively; all p < 0.05). Meanwhile, the H2-O2 intervention significantly decreased diastolic nighttime ambulatory blood pressure by 2.7 ± 6.5 mmHg (p < 0.05). All blood pressures were unaffected in placebo group (all p > 0.05). When stratified by age (aged 50-59 years versus aged 60-70 years), participants in the older H2-O2 group showed a larger reduction in right arm SBP compared with that in the younger group (p < 0.05). In addition, the angiotensin II, aldosterone, and cortisol levels as well as the aldosterone-to-renin ratio in plasma were significantly lower in H2-O2 group compared with baseline (p < 0.05). No significant differences were observed in the Air group before and after the intervention. Conclusion: Inhalation of a low-dose H2-O2 mixture exerts a favorable effect on blood pressure, and reduces the plasma levels of hormones associated with hypertension on renin-angiotensin-aldosterone system and stress in midlife/older adults with hypertension.
Source & links
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