“Hyperbaric oxygen therapy reverses aging”

## The Study That Launched the Headlines Hadanny et al. (2020, *Aging*) randomised 35 healthy older adults (mean age 64) to 60 HBOT sessions over 90 days. Blood cell analysis showed telomeres lengthened by ~20% and senescent T-cells decreased by ~37%. This was interpreted as "reversal of aging." ## Why We Should Be Cautious 1. **Sample size**: 35 participants is far too small to draw conclusions. Telomere length varies substantially and is influenced by many factors. 2. **Blood cells vs. tissue**: Telomere changes were measured in peripheral blood mononuclear cells — not in target tissues like muscle, brain, or cardiovascular tissue. 3. **Non-replication**: As of 2024, no independent group has replicated these findings with a larger sample. 4. **Clinical significance**: Telomere lengthening of 20% in blood cells has unknown clinical relevance. Telomere length is one of many aging biomarkers, and its relationship to actual longevity in humans is more complex than often presented. 5. **Cost and access**: HBOT is expensive (~€100–200/session) and requires medical facilities. The risk/benefit calculation at this evidence level is poor.