Scientists do not yet have a complete answer.
But several other clues from her biology may help.
A Gut Microbiome That Looked Surprisingly Young
Another remarkable finding came from her gut.
The human digestive system contains trillions of microorganisms, including bacteria that interact with food, metabolism, immunity and other biological processes.
Together, these microorganisms are commonly referred to as the gut microbiome.
As people age, the composition and diversity of the microbiome can change. Some bacterial groups decline, while other potentially harmful patterns may become more prominent.
In Branyas's case, researchers found elevated levels of bacteria from the Actinobacteriota group, including Bifidobacterium, a genus widely studied for its role in the human gut.
The University of Leicester reported that these bacteria are generally associated with younger microbiome profiles and are also found at elevated levels in some centenarians and supercentenarians.
This does not prove that Bifidobacterium made Branyas live to 117.
That would be far too strong a conclusion.
Her microbiome may have been partly a consequence of her diet, genetics, lifestyle or other characteristics rather than the original cause of her longevity.
Nevertheless, it provides another piece of the puzzle.
It suggests that exceptionally long-lived people may retain some characteristics of a healthier, more resilient gut ecosystem even at an age when many age-associated changes have already occurred.
Her Blood Revealed Very Low Inflammation
Inflammation is another major area of ageing research.
Inflammation is not inherently bad.
The immune system uses inflammation to respond to infection and injury. Short-term inflammation is an important part of normal healing.
The problem can arise when inflammatory activity remains elevated for long periods.
Researchers sometimes refer to this persistent, low-grade inflammation associated with ageing as inflammaging.
Long-term inflammation has been associated with numerous age-related diseases and biological changes.
When researchers analyzed thousands of proteins circulating in Branyas's blood, they found patterns suggesting unusually low inflammation.
The University of Leicester team specifically reported that her blood-protein profile showed very low inflammatory activity for someone of such advanced age.
That finding is important because chronic inflammation can influence multiple systems at once.
It can affect blood vessels, metabolism, immune regulation and other processes involved in healthy ageing.
Branyas's biology appeared to have maintained relatively effective control over this inflammatory burden.
That does not mean she had no inflammation.
Nor does it mean inflammation can simply be “switched off” to extend life.
Instead, the finding suggests that maintaining appropriate immune regulation may be one feature of exceptional healthy ageing.
Her Body Was Extremely Efficient at Handling Lipids
Another striking feature was her lipid metabolism.
Lipids include fats and fat-like molecules that perform essential functions in the human body.
Cholesterol, for example, is necessary for cell membranes and hormone production. But abnormal levels and transport of certain lipids can contribute to cardiovascular disease.
According to researchers involved in the study, Branyas had an unusually favorable lipid profile, including very low cholesterol levels and efficient lipid transport and metabolism.
The researchers suggested that both genetic factors and lifestyle may have contributed.
Her biology appeared particularly effective at processing potentially harmful molecules.
This could have reduced some of the biological stress placed on her cardiovascular system over the decades.
Cardiovascular disease is one of the major threats associated with ageing, so maintaining healthy lipid metabolism for an exceptionally long period could have been highly protective.
But once again, scientists must be careful.
A favorable lipid profile alone cannot explain 117 years of life.
Longevity is almost certainly the result of many interacting systems rather than one protective laboratory value.
Genetics May Have Given Her an Advantage
Genes were another major part of the investigation.
The researchers identified genetic characteristics that may have contributed to her extraordinary longevity.
The study found rare genetic variants associated with pathways related to lifespan and protection from age-related disease. Researchers also reported variants associated with lipid regulation and cardiovascular health.
Some of these variants were related to biological pathways previously implicated in longevity research.
But there is no single gene that guarantees an exceptionally long life.
According to NIH MedlinePlus Genetics, longevity is influenced by both genetic and environmental factors. Estimates suggest genetics may account for roughly 25% of variation in human lifespan, although the precise contribution differs across studies and the specific genetic mechanisms remain incompletely understood.
Research has identified genes and variants associated with longevity, including FOXO3 and APOE, among others.
Yet these variants are not present in every centenarian.
This is one reason scientists increasingly think of longevity as a complex, polygenic trait.
Hundreds or thousands of small biological influences may interact.