A new analysis of data gathered from a small Indigenous population in the Bolivian Amazon suggests some of our basic assumptions about the biological process of aging might be wrong.
Inflammation is a natural immune response that protects the body from injury or infection. Scientists have long believed that long-term, low-grade inflammation — also known as “inflammaging” — is a universal hallmark of getting older. But this new data raises the question of whether inflammation is directly linked to aging at all, or if’s linked to a person’s lifestyle or environment instead.
The study, which was published today, found that people in two nonindustrialized areas experienced a different kind of inflammation throughout their lives than more urban people — likely tied to infections from bacteria, viruses and parasites rather than the precursors of chronic disease. Their inflammation also didn’t appear to increase with age.
Scientists compared inflammation signals in existing data sets from four distinct populations in Italy, Singapore, Bolivia and Malaysia; because they didn’t collect the blood samples directly, they couldn’t make exact apples-to-apples comparisons. But if validated in larger studies, the findings could suggest that diet, lifestyle and environment influence inflammation more than aging itself, said Alan Cohen, an author of the paper and an associate professor of environmental health sciences at Columbia University.
“Inflammaging may not be a direct product of aging, but rather a response to industrialized conditions,” he said, adding that this was a warning to experts like him that they might be overestimating its pervasiveness globally.
“How we understand inflammation and aging health is based almost entirely on research in high-income countries like the U.S.,” said Thomas McDade, a biological anthropologist at Northwestern University. But a broader look shows that there’s much more global variation in aging than scientists previously thought, he added.
The study “sparks valuable discussion” but needs much more follow-up “before we rewrite the inflammaging narrative,” said Bimal Desai, a professor of pharmacology who studies inflammation at the University of Virginia School of Medicine.
Inflammation is different in different places.
In the study, researchers compared blood samples from about 2,800 adults between 18 and 95. People in the more industrialized Chianti region of Italy and in Singapore both showed the types of proteins that signal inflammaging.
The Tsimane group in Bolivia and the Orang Asli group in Malaysia, on the other hand, had different inflammatory markers likely tied to infections, instead of the proteins marking inflammaging. (The four datasets used blood samples with subjects’ informed consent, whether written or verbal, and institutional approval.)
The fact that inflammation markers looked so similar in groups from industrialized regions, but so different from the others, is striking, said Aurelia Santoro, an associate professor at the University of Bologna who was not involved in the study. “This suggests that immune cells are activated in fundamentally different ways depending on context.”
The Tsimane population’s protein markers were less linked to inflammaging than the Orang Asli’s; authors speculated that this might be because of differences in lifestyle and diet.
Some experts questioned the findings’ significance. Vishwa Deep Dixit, director of the Yale Center for Research on Aging, said it’s not surprising that lifestyles with less exposure to pollution are linked to lower rates of chronic disease. “This becomes a circular argument” that doesn’t prove or disprove whether inflammation causes chronic disease, he said.
Either way, the findings need to be validated in larger, more diverse studies that follow people over time, experts said. While they had lower rates of chronic disease, the two Indigenous populations tended to have life spans shorter than those of people in industrialized regions, meaning they may simply not have lived long enough to develop inflammaging, Dr. Santoro said.
The problem may be tied to urban living.
Because the study looked at protein markers in blood samples, and not specific lifestyle or diet differences among populations, scientists had to make educated guesses about why industrialized groups experience more inflammaging, Dr. Cohen said.
Dr. McDade, who has previously studied inflammation in the Tsimane group, speculated that populations in non-industrialized regions might be exposed to certain microbes in water, food, soil and domestic animals earlier in their lives, bolstering their immune response later in life.
At the same time, people in urbanized, industrial environments are “exposed to a lot of pollutants and toxins,” many of which have “demonstrated pro-inflammatory effects,” he said. Diet and lifestyle could also play a part: The Tsimane tend to live in small settlements with their extended family and eat a largely plant-based diet, he said.
There might also be good and bad types of inflammation, Dr. Cohen said. While the Indigenous populations did experience inflammation from infection, those levels weren’t tied to chronic disease later in life. That could mean that the presence of inflammation alone isn’t as bad as we thought, he added.
It’s not clear if people can do anything to manage inflammaging late in life. People who want to age more healthily may be better off eating better and exercising more to regulate immune response in the long run, instead of focusing on drugs or supplements advertised to target inflammation, Dr. Cohen said.
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