The Four Types of Aging

Two older women walking in a field

Staying healthy isn’t just about how old you get.

It’s about how you get old.

That’s according to emerging research by Dr. Michael Snyder, a geneticist at Stanford University’s School of Medicine. Snyder and his team have discovered what he calls the body’s “ageotypes,” specific ways in which certain people age. People with different ageotypes grow differently over the course of their lifetimes, experiencing aging according to distinct patterns. These create, in Snyder’s words, “very distinct profiles” which can tell someone an enormous amount about how their body will change over time.

And perhaps more importantly, these profiles can tell people how to take better care of themselves as they grow older.


The Four Ageotypes

The body ages at different rates, a phenomenon that doctors call “biological” vs. “chronological” age. Take a chronologically 45-year-old individual, for example, with a biologically 55-year-old liver but biologically 35-year-old skin. This would mean that although the person had recently celebrated their 45th birthday, their liver more closely resembled that of a median 55-year-old while their skin resembled that of a median 35-year-old.

These effects are often the result of lifestyle choices by the individual. It’s how doctors note the aging effect that cigarettes have on a smoker’s lungs or the effect of weight issues on the heart.

However, the ageotype insight is that everyone is also predisposed to biologically aging in different ways. Someone’s ageotype defines how they will get older, with parts of their body aging faster or more slowly than others.

“The way we’re thinking about it,” says Snyder, “is like a car. You buy a car and it gradually wears out over time, but some parts wear out faster than others … And that’s kind of what we think we’re measuring here.”

As of October 2020, Snyder’s team has identified four distinct ageotypes: metabolic agers, or people whose immune systems age fastest; immune agers; kidney (or “nephrotic”) agers; and liver (or “hepatic”) agers.

A classic “immune ager,” for example, might be chronologically 40 with the immune system of a 42-year-old and a metabolism that is biologically 32. This person would likely remain more slender in old age but would also be increasingly prone to immunocompromise and related conditions over the course of their life. A metabolic ager, on the other hand, might retain a healthy immune system while increasingly struggling with diabetic risk factors and weight as they grow older.

And Snyder is quick to point out that research is still ongoing. There will be more than four types, he says, referencing cardiovascular aging in particular as a subject for ongoing study.

It’s also important to note that individuals can age in multiple different ways and will typically have a combination of ageotypes to varying degrees. A primarily nephrotic ager, for example, may also have a partial haptic ageotype, meaning their kidney functions are likely to age fastest, but their liver may develop a bit faster than the median, too. Other individuals may have a mix of ageotypes without a single dominant pattern. It is a highly individual, highly specific profile.


In Search of Biological Youth

Like most issues surrounding health, ageotypes are based on a combination of genetic predisposition and lifestyle choices. Knowing this, Snyder hopes to use his research into ageotypes in the opposite direction. If behavior can help accelerate aging, it can also help slow the process.

“The holy grail is being able to use this information actionably,” he says. “What you would do is suggest programs that might improve what people are doing. So if they are a metabolic ager, exercise and food would be the thing.”

Snyder believes this personalized and proactive approach to health will make a big difference in allowing people to live well longer.  Right now, he says, “I think the medical system is totally broken: At so many different levels it’s very reactive. We work on people when they’re sick, but we really don’t focus on keeping people healthy.”

Applying ageotypes to treatment would be a matter of helping people understand what their body needs as it gets older.

While the research remains new, an individual’s ageotype can be identified by studying the blood samples for molecules produced as a byproduct of bodily functions. Different levels of chemicals can indicate whether, say, the haptic system has aged more quickly than the metabolic system or vice versa.

Someday, this may enable doctors to create medical and, more often, lifestyle plans to help someone address the way their body is specifically aging. While far from the cure for old age, Snyder hopes that people can stay healthier longer once they can build their life around their body’s specific needs.

“We haven’t found the solution,” he says. “There’s no magic pill. I think we’ve just found the way to measure you in incredible detail. So we can see how you’re headed downhill and that’s the first step to trying to stop yourself from heading downhill.”

Ageotypes may help unlock new ways to treat chronic issues, and may allow people to extend their health and vitality longer than treatment currently allows. It is not, however, the long-sought path to eternal youth and energy. On that note, Snyder counsels that nothing can beat the advice that doctors have given for generations: “Right now the closest thing we have to a fountain of youth is exercise.”

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