Protocol
Hyperbaric Oxygen (HBOT) · 60 sessions at 2.0 ATA
(Aging, 2020; PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 32589613): randomized controlled trial People are assigned to the treatment or a comparison by chance, so the groups differ only in what they received. It is the design that can show cause and effect. in healthy older adults, 60 sessions; some cognitive measures improved against control.
Grade C: human trials exist, but they are small, mixed or not yet repeated. This is not a finding that it does not work. How to read a grade →
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How this letter has changedLatest: October 2026 · Downgraded.
The record held B on Hadanny et al. (Aging, 2020; PMID 32589613), one randomized trial, with Hachmo et al. (Aging, 2020; PMID 33206062), an uncontrolled study from the same center, beside it, and had sat in the replication The same finding reproduced by a separate research group. A result seen once can be chance or bias; a replicated one is harder to explain away. baseline since September as a known contradiction of Rule 03. A search in October found no independent randomized trial. A single positive trial nobody has repeated is C. Applied the written grade definition under the editor's standing instruction of October 2026 (Arnold Sandlow, D.C.).PMID 32589613 PMID 33206062
Every change to a letter on this site is dated and published. The full evidence log →
This protocol is 60 sessions of breathing pure oxygen in a pressurized chamber. In one study from one group, healthy older adults improved on some thinking tests. In a second study by the same group, with no comparison group, the ends of chromosomes in blood cells grew longer. No outside group has repeated these results.
Hadanny et al. (Aging, 2020; PMID 32589613): randomized controlled trial in healthy older adults, 60 sessions; some cognitive measures improved against control. Hachmo et al. (Aging, 2020; PMID 33206062): the same group's uncontrolled trial in 35 adults aged 64 and over; telomere length in isolated blood cells rose, by 37.63 percent in one lymphocyte subset and less in others, and senescent T-helper cells fell. One randomized trial from one center, surrogate and cognitive-test endpoints The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score., no clinical outcome: C.
Why this gradeGrade C, small or unreplicated trials. The reasoning, and what the grade does not cover.
Grade C: one randomized trial from one group, Hadanny et al. (Aging, 2020; PMID 32589613), in which 60 sessions improved some cognitive measures in healthy older adults, and the same group's uncontrolled trial in 35 adults, Hachmo et al. (Aging, 2020; PMID 33206062), in which telomere length in isolated blood cells rose. Under the written rule a single positive randomized trial nobody has independently repeated is C; the telomere finding is uncontrolled and would not carry a letter on its own. Moved from B in October 2026.
WHAT THIS GRADE DOES NOT COVERany clinical outcome such as disease, disability or mortality, which no cited trial measured; pressures below 2.0 ATA or air-filled chambers, which were the sham A fake version of a procedure or device used as the comparison, so participants cannot tell which one they received. condition; and the established medical uses of hyperbaric oxygen, such as decompression illness, which are outside this protocol.
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The evidence, in fullTwo papers, each linked to its PubMed record.
Hachmo et al. (Aging (Albany NY), 2020; PMID 33206062): clinical trial: HBOT increased telomere length and decreased senescent cell fraction. Hadanny et al. (Aging (Albany NY), 2020; PMID 32589613): RCT Randomized controlled trial: people are assigned to the treatment or a comparison by chance, so the groups differ only in what they received. It is the design that can show cause and effect.: HBOT improved some cognitive measures in healthy older adults.
Telomere length and senescent cell percentage at baseline and after 60 sessions: these were the endpoints reported by Hachmo et al. (Aging, 2020; PMID 33206062). Cognitive function using a validated battery at baseline and post-protocol if cognitive enhancement is the target. Session count and ATA pressure must match the studied protocol: partial protocols have not been studied.
Evidence notes: not independently replicated, randomized trial
Endpoint graded: Telomere length, senescent T cells and cognitive measures in healthy older adults (surrogate)
Last reviewed: July 2026
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("hyperbaric oxygen"[tiab]) AND (healthy[tiab] OR aging[tiab] OR "older adults"[tiab]) AND (telomere[tiab] OR cognit*[tiab] OR senescen*[tiab]) AND (randomized controlled trial[pt] OR clinical trial[pt])Grades move when new trials publish. A free monthly email lists every grade EBL moved, with the reason and the trial behind it: the sign-up is on the Evidence Log →