The tiny bacteria living inside our intestines may reveal important clues about healthy aging, according to a new study published in Nature Communications.
Researchers from the University of Gothenburg have found that older adults who are more physically frail tend to have less diverse and less healthy gut bacteria. The findings suggest that the trillions of microbes living in the digestive system could one day help doctors identify older people who are at greater risk of illness, falls, disability, and even early death.
The human gut is home to trillions of bacteria, viruses, and other microorganisms. Together they are known as the gut microbiota. Although many people think of bacteria only as germs that cause disease, most gut bacteria are helpful.
They help digest food, produce vitamins, support the immune system, protect against harmful microbes, and communicate with many parts of the body, including the brain. Over the past decade, scientists have discovered that changes in gut bacteria may be linked to conditions such as obesity, diabetes, heart disease, depression, dementia, and healthy aging.
As people grow older, many experience a condition known as frailty. Frailty is not simply getting older. It is a medical condition in which the body becomes less able to recover from illness or stress.
Frail older adults are more likely to fall, lose muscle strength, become disabled, spend time in hospital, and die earlier than healthier people of the same age. Understanding why frailty develops has become an important goal because the world’s population is aging rapidly.
To investigate whether gut bacteria are linked with frailty, researchers studied 2,081 Swedish women aged between 75 and 80 years who were part of the SUPERB study.
The team analysed genetic material from bacteria found in stool samples to identify which microbes were present and what they were likely to be doing. The researchers then compared these findings with each participant’s level of frailty.
Instead of relying on a single test, the scientists used the Frailty Mortality Index, or FMI. This index combines information about physical ability, body function, mental health, and other factors to estimate both frailty and the future risk of death.
The results showed a clear pattern. Women with higher frailty scores had much lower bacterial diversity in their intestines. They also had fewer microbial genes and reduced predicted bacterial functions.
In other words, not only were there fewer different types of helpful bacteria, but the bacteria that remained appeared less able to carry out important biological tasks.
The researchers identified 404 bacterial species that were significantly linked with frailty. Many of these same bacterial patterns were also found in a completely separate study involving 1,448 older men and women from China. Finding similar results in two very different populations strengthens confidence that the associations are real rather than occurring by chance.
Lead researcher Marina Vilar Geraldi said the findings show that the gut microbiota reflects important aspects of frailty in older adults.
Senior researcher Professor Mattias Lorentzon added that future studies will investigate whether these bacterial patterns could eventually help doctors identify older adults who need extra support or whether changing the gut microbiota might reduce frailty.
The researchers stress that this study found an association, not proof of cause and effect. It is still unknown whether unhealthy gut bacteria contribute to frailty or whether frailty itself changes the gut microbiota. Larger long-term studies and clinical trials will be needed to answer this important question.
Overall, this is a strong study because it included more than 3,500 older adults from Sweden and China and confirmed many findings across two independent populations.
However, because it was observational, it cannot show that gut bacteria directly cause frailty. Even so, the research adds to growing evidence that the gut microbiota plays an important role in healthy aging and may eventually become part of future health assessments or treatments for older adults.
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Source: University of Gothenburg.
