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HBOT and Longevity: What the Telomere Study Did and Did Not Show

HBOT longevity claims rest on one 2020 study: 30 older adults, 60 sessions, longer telomeres in blood cells, no control group. What it shows and what it lacks.

Updated September 14, 2026
9 min read
by Hyperbaric.app

This content is for informational purposes only and does not constitute medical advice. Always consult a healthcare professional. Read full disclaimer

Most claims that hyperbaric oxygen therapy (HBOT) slows ageing trace back to one 2020 study from Israel. Thirty healthy adults aged 64 and over completed 60 HBOT sessions, and afterwards telomeres in several types of immune cells in their blood measured more than 20% longer, with fewer senescent T cells. The study had no control group, and only 25 participants were included in the telomere analysis. Nobody has shown that HBOT slows ageing, prevents age-related disease or extends life, and ageing is not on any list of accepted HBOT indications.

This article looks at the science question: what that study measured, its limits, and what better evidence would look like. If you want the practical side (skin, energy, wellness chambers, cost and what to be sceptical of), read our companion guide to HBOT for anti-aging, which covers what to check before you pay for sessions.

What did the 2020 telomere study do?

The study, by Hachmo, Hadanny, Efrati and colleagues, was published in the journal Aging in November 2020. It was carried out at Shamir (Assaf-Harofeh) Medical Center in Israel, where several authors are also affiliated with Tel Aviv University.

QuestionWhat the study did
Who took part?35 healthy, independently living adults aged 64 and older were enrolled; 30 completed baseline tests and the full treatment course
What was the treatment?60 daily sessions, five a week over three months: 100% oxygen by mask at 2 ATA for 90 minutes, with 5-minute air breaks every 20 minutes, in a multiplace chamber
What was measured?Telomere length (by flow-FISH) and the proportion of senescent T cells in blood immune cells, at baseline, at sessions 30 and 60, and 1-2 weeks after the last session
Control group?None. Every participant received HBOT
How many were analysed?25 for telomere length and 20 for senescent cells, after samples of low quality were excluded

What it found

  • Telomere length in T helper cells, cytotoxic T cells, natural killer cells and B cells increased significantly, by more than 20%.
  • B cells changed most: telomeres were 29.39% ± 23.39 longer at session 60 and 37.63% ± 52.73 longer after the course. The large spread shows how much individuals varied.
  • Senescent T helper cells (a type of "worn-out" immune cell that no longer divides) fell by 37.30% ± 33.04 after the course. Senescent cytotoxic T cells fell by 10.96% ± 12.59.

The authors concluded that HBOT "may induce significant senolytic effects". The study was funded by a research grant from the Sagol network for neuroscience. Several authors disclosed that they work for AVIV Scientific Ltd, and the senior author disclosed that he is a shareholder.

What are the study's limitations?

The authors listed four limitations themselves:

  1. Small sample size.
  2. No control group. Without one, you cannot tell how much the measurements would have changed anyway, for example through natural variation between blood samples or drift in laboratory measurements over three months.
  3. Unknown duration. Measurements stopped 1-2 weeks after the last session, so nobody knows whether the changes last.
  4. Telomerase not measured. The enzyme that can lengthen telomeres was not assessed.

There are also broader reasons for caution.

Blood telomere length can change when the mix of cells changes

The study measured cells in the blood, which are constantly replaced. A 2011 study followed divers exposed to intense hyperbaric oxygen for 12 months and found telomere elongation in some white blood cell types but not others. Its title describes this as "telomere elongation followed by telomere length reduction". The authors suggested that, at least in granulocytes, the longer average telomeres may come from newly produced cells with longer telomeres entering the blood, and that this faster cell turnover might itself be relevant to tissue ageing. In other words, a longer average telomere in a blood sample is not the same as existing cells becoming younger.

Telomere length is an uncertain marker of ageing

A review in the Journals of Gerontology concluded that although telomeres are involved in cellular ageing, the human evidence that telomere length works as a biomarker of ageing is "equivocal". More recently, a group of ageing researchers writing in Nature Medicine noted that there is still no consensus on how biomarkers of ageing should be validated before they are used to judge longevity interventions. A change in a biomarker is not the same as a longer or healthier life.

Independent follow-up is still needed

A 2021 commentary in Rejuvenation Research summarised the telomere study and the same group's cognitive trial as preliminary results that "require follow-up", noting that the durability of the changes "is yet to be determined". Most of the human data on HBOT and ageing markers come from this one research group.

What else has the same group studied?

The Sagol Center team has published several related studies in healthy older adults using the same 60-session, 2 ATA protocol:

  • Thinking skills. A randomised trial of 63 adults over 64 found greater improvement in global cognitive function, attention and information processing speed after HBOT than in a control group, along with increased blood flow in parts of the brain. The control group received no intervention rather than a sham, and participants knew which group they were in, which the authors list as a limitation.
  • Physical fitness. A randomised trial of 63 sedentary adults over 64 reported that maximal oxygen consumption per kilogram rose by 1.91 ml/kg/min after HBOT, with increased blood flow to the heart muscle. Again the control group had no intervention and was not blinded.
  • Skin. A small study took skin biopsies from 13 men and found more collagen, longer elastic fibres, more blood vessels and fewer senescent cells after HBOT than after a three-month period without treatment. Our anti-aging guide discusses what that does and does not mean for how skin looks.

These are consistent with each other, but they share the same design weaknesses: small numbers, no sham comparison, short follow-up and a single centre.

Why might oxygen affect ageing at all?

The team's proposed mechanism is the hyperoxic-hypoxic paradox. Cells sense changes in oxygen level, not just the absolute level. So when oxygen rises sharply during a session and then falls back, cells may respond as if oxygen were scarce, switching on some of the same repair and blood-vessel-growth signals that low oxygen normally triggers. The air breaks in the protocol are designed to create those fluctuations.

A separate line of research, from the University of Pennsylvania, found that a single 2-hour exposure to 2.0 ATA oxygen doubled circulating CD34+ stem/progenitor cells in humans, and that levels were eight times higher over a course of 20 treatments.

These mechanisms are biologically plausible and worth studying. But a plausible mechanism, and changes in blood markers, do not show that a person ages more slowly.

What would stronger evidence look like?

To show that HBOT meaningfully affects human ageing, studies would need:

  • A sham control. A sham chamber session can be convincing. A 2023 Geneva trial found that compressing volunteers to 1.3 ATA with added ventilation, heating and faster compression led most of them to believe they had received a full 2.0 ATA treatment.
  • More people, in more than one centre, ideally run by researchers without a commercial interest in HBOT.
  • Outcomes that matter in daily life, such as physical function, independence, disease or mortality, not only blood biomarkers.
  • Long follow-up, to see whether any change lasts months or years after treatment ends.
  • Careful safety reporting. A course at 2.0 ATA or more commonly causes temporary short-sightedness, and middle ear barotrauma is one of the most common side effects of HBOT, according to a review of HBOT side effects.
  • Clarity about dose. The study used 2 ATA with 100% oxygen. "Mild" soft chambers at around 1.3 ATA were not tested, and the Undersea and Hyperbaric Medical Society (UHMS) considers mild hyperbaric treatment unproven. Our hard-shell vs soft-shell guide explains the difference.

What this means for you

The honest summary is that HBOT for longevity is an open research question. The 2020 study is interesting early biology, not proof that HBOT slows ageing. If you choose to try it anyway, know which protocol a clinic is using and how it compares with the studied one, understand the side effects (see HBOT side effects), and discuss it with your doctor first.

When you want to compare providers, you can find a hyperbaric clinic near you in the directory.

Sources

This article is for information only and is not medical advice. Talk to a qualified physician before starting HBOT for any reason.

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