The idea of someone "aging backward" seems like an innocent joke, but a small clinical study in California has suggested there might be more to it. Turns out, it might be possible to reverse the body's epigenetic clock, which measures a person's biological age. At least to some extent.

For one year, nine healthy volunteers took a cocktail of three common drugs — growth hormone and two diabetes medications — and on average lost 2.5 years of their biological ages, measured by analyzing marks on a person's genomes. If that wasn't enough, their immune systems also showed signs of rejuvenation.

The results were a surprise even to researchers. However, they do point out that the findings are preliminary because the trial was small and did not include a control group.

"I'd expected to see slowing down of the clock, but not a reversal," Steve Horvath, a geneticist at the University of California, Los Angeles, who conducted the epigenetic analysis, told Nature. "That felt kind of futuristic."

The trial was carried out mainly to test whether growth hormone could be used safely in humans to restore tissue in the thymus gland, which is located in the chest between the lungs and the breastbone, and is crucial for efficient immune function. White blood cells are produced in the bone marrow and then mature inside the thymus, where they become specialized T cells that help the body to fight infections and cancers. The gland, however, starts to shrink after puberty and increasingly becomes clogged with fat.

9 white men between 51 and 65 years of age participated in The Thymus Regeneration, Immunorestoration, and Insulin Mitigation (TRIIM) trial. It was led by immunologist Gregory Fahy, the chief scientific officer and co-founder of Intervene Immune in Los Angeles, and was approved by the US Food and Drug Administration back in May 2015.

Blood samples showed that the blood-cell count was rejuvenated in each of the participants. The researchers also used magnetic resonance imaging (MRI) to determine the composition of the thymus at the start and end of the study. In seven participants, accumulated fat had been replaced with regenerated thymus tissue.

Horvath used four different epigenetic clocks to assess each patient’s biological age. He found significant reversal for each trial participant in all of the tests.

“This told me that the biological effect of the treatment was robust,” he said. Moreover, the effect persisted in the six participants who provided a final blood sample six months after stopping the trial too.

Regenerating the thymus could be useful in people who have underactive immune systems, including older people.

Consider yourself Benjamin Buttoned.