One hundred adults in Shenyang, China, breathed pure oxygen at 2.5 atmospheres for 30 sessions over roughly six weeks while researchers sampled their blood four times. Relative telomere length in their immune cells rose steadily, reaching about 29 percent above baseline by session 30, and the proportion of “worn-out” CD8 T cells that had lost the CD28 and CD27 co-stimulatory receptors fell modestly. Inflammatory cytokines did not move in any consistent direction across the group. The response was uneven: younger participants, women, and people with normal BMI showed the clearest reductions in senescent-looking T cells, while older, male, and overweight participants showed little. There was no control group, no sham chamber, and no randomization, so none of this establishes that hyperbaric oxygen caused the changes. The paper is best read as a large, well-instrumented observational time series that generates hypotheses rather than as evidence of an anti-aging intervention.
The idea that you can rewind a piece of the aging process by sitting in a pressurized chamber has been circulating in longevity circles since a small Israeli trial in 2020 reported telomere lengthening and fewer senescent immune cells after 60 hyperbaric sessions. This new study from China Medical University is the largest attempt yet to reproduce that signal, and it does something the earlier work did not: it samples blood repeatedly during treatment rather than only at the end, and it asks who responds rather than assuming everyone does.
The big idea is dose timing and personalization. By measuring at baseline and after 10, 20, and 30 sessions, the team could watch trajectories rather than endpoints. What they saw was two different shapes. Telomere signal climbed in a straight line and kept climbing. Senescent-phenotype T cells dropped early, at around 10 sessions, then drifted partway back. Inflammatory markers wobbled without direction.
That divergence matters. A biomarker that rises monotonically looks like a dose response. Markers that fall and then rebound look more like a transient perturbation, or like statistical noise settling back toward its long-run average. The authors are careful about this, and they raise an alternative explanation that deserves more attention than it usually gets: telomere length was measured in bulk immune cells, and senescent CD8 cells are known to carry unusually short telomeres. Remove some of those cells from the mixture and the average telomere signal goes up without a single telomere getting longer.
The personalization finding is the genuinely new contribution. Age, sex, and body mass index all appeared to shape the response, with the youngest participants showing reductions in senescent CD8 cells several times larger than the group average. But that youngest group contained only 14 people, and the confidence intervals around their apparently dramatic response are wide enough to accommodate almost anything.
The most important structural fact about this study is what it lacks. There was no control arm and no sham exposure. Seventy-three of the 100 participants were patients receiving hyperbaric oxygen for a medical reason, most commonly bone infection or bone death in the hip, conditions that produce systemic inflammation and that were being actively treated during the study window. Improvement in an inflammatory blood profile in that population is exactly what successful treatment of the underlying disease would look like. Disentangling that from any effect on aging biology is impossible with this design, and the authors say so.
Actionable Insights
The single strongest result here is telomere signal, with a standardized effect size of Cohen’s d = 0.70 after 30 sessions (roughly 0.46 to 0.94). In plain terms, a d of 0.70 means that if you picked one person’s post-treatment reading and one pre-treatment reading at random, the post reading would be higher about 69 percent of the time. That is a real, visible shift, not a rounding error.
The immune cell results are much smaller. The reduction in senescent-looking CD8 T cells was d = 0.25 to 0.37, which translates to about one to two fewer senescent cells per hundred CD8 T cells, moving the group average from roughly 48.6 percent to 47.1 percent. Inflammatory markers showed no group-level effect at all.
Weigh that against the cost. Thirty sessions at 2.5 atmospheres is roughly 60 to 65 hours inside a chamber across six weeks, and US self-pay pricing commonly runs $150 to $450 per session, so $4,500 to $13,500 for this protocol.
The honest take-home: nothing here justifies buying a course of hyperbaric oxygen for longevity. The one large effect is measured by a method that cannot distinguish true telomere lengthening from a change in which cells were in the tube.
Context and Source
- Open Access Paper: Hyperbaric Oxygen Therapy Modulates Immune Aging in a Personalized Manner: A Linear Mixed-Effects Analysis
- Authors: Hai-Tao Chu, Hang Zhao, Shan-Shan Wang, Xin Meng, Di Wang, Xiao-Bo Zhu, Yang Wang, Xue-Wei Yang
- Institution: Department of Hyperbaric Oxygen Medicine and Department of Surgical Oncology, the First Hospital of China Medical University, Shenyang, China. Two authors are affiliated with Canta Medical Tech. Co., Ltd., the commercial sponsor.
- Country: China
- Journal: Immunity and Ageing (BMC / Springer Nature).
- Impact evaluation: The impact score of this journal is 8.3 (2025 Journal Impact Factor; CiteScore approximately 10.1), evaluated against a typical high-end range of 0 to 60+ for top general science, therefore this is a Medium impact journal.