At this very moment, some parts of you may be biologically older than others.
That’s according to a study recently published in Cell, which concluded that body parts don’t universally age at the same rate. Some organs start to show signs of wear and tear long before others, the researchers found.
The human body is “kind of like a car: Even though the whole thing gets older, some parts wear out faster,” Michael Snyder, PhD, who directs the Center for Genomics and Personalized Medicine at the Stanford University School of Medicine, told Health. Snyder was not involved in the new study, but has previously researched the timing of human aging.
Tracking those different timelines, he said, helps scientists better understand the aging process—potentially leading, someday, to tools that can help slow it.
For the new study, researchers from the Chinese Academy of Sciences analyzed proteins to determine how and when different parts of the body age. “Proteins are the cornerstone of life,” they wrote in the paper. But a protein-based “blueprint of aging across human tissues remains uncharted.”
To change that, they collected 516 tissue samples from 76 people, ages 14 to 68, who died from brain injuries. The tissue samples came from organs including the heart, lungs, liver, pancreas, spleen, intestines, adrenal glands, and skin. While 76 people isn’t many, Snyder said the study was “novel” for analyzing so many tissues from so many different organs.
The researchers analyzed those tissues to identify aging-related changes in proteins throughout the body and in specific organs. They also mapped out whether some organs seem to age more quickly than others.
Overall, they found, the aging process seems to speed up around age 50.
But different organs seem to age on different timelines. Many examined in the study showed significant aging-related changes between 45 and 55, while some began aging even earlier.
By age 30, the aorta (the body’s largest artery), spleen, and adrenal glands (which produce hormones) already showed noticeable changes in their proteins, the researchers found.
The “early and pronounced aging of the aorta,” they wrote, suggests that aging-related changes to blood vessels may be an important driver of overall aging.
In a previous study, Snyder and his colleagues found that the body goes through two major periods of aging: one at 44 and another at 60. While those numbers don’t exactly match the ones in the new study, they’re not far off, Snyder said. And both studies support the idea that aging doesn’t happen all at once—and may start earlier than you think.
“A lot of these processes are happening silently in our bodies,” Manisha Parulekar, MD, an associate professor and chief of the Division of Geriatrics at Hackensack University Medical Center, who was not involved in the new research, told Health. “You cannot just go by looking at how you are feeling that particular day. This very slow, but constantly happening, process is [taking place] in the background.”
The new study’s findings are “interesting,” but ultimately difficult to translate to medical practice, Vadim Gladyshev, PhD, a professor of medicine at Harvard Medical School who studies aging but was not involved in the new study, told Health.
Gladyshev’s research suggests that organ-specific aging is associated with the development of disease in those body parts. But more research is needed, he said, to understand what specific shifts—like age-related changes in proteins—really mean.
“It’s very hard to interpret,” he said. “We don’t know, is this change a bad change, a neutral change, or a [beneficial] response of an organism to aging?”
Nonetheless, the new study revealed some “fascinating” findings worthy of further study, Parulekar said. For example, the researchers found that amyloid—a protein primarily associated with Alzheimer’s disease—accumulates in other aging organs as well.
The researchers also found proteins in the blood that seem to cause aging. That’s an interesting finding, Snyder said, and one that lays the groundwork to potentially develop new therapies targeting those proteins.
“You could, in principle, clear those proteins” with drugs and potentially reverse aging processes, he told Health—although much more research would be needed to prove that.
While the new study opens doors for further research, Parulekar said following tried-and-true habits is still the best way to live as long and healthy a life as possible.
Eat a balanced diet, stay physically active, get enough sleep, manage stress, practice mindfulness, and stay connected with your community, she suggested.
You’ve probably heard all of those things before. But the new study emphasizes that it’s time to stop putting them off—because aging, especially in some parts of the body, starts sooner than you might want to admit.
“Incorporating these habits as early as we can, in our 20s and our 30s, may help us slow down this clock,” Parulekar said.
