healthHealth and Medicine

Study Suggests That Americans May Be Aging More Slowly Over Time


Robin Andrews

Science & Policy Writer

Biological age is a subjective concept, but that doesn't mean it's entirely flawed. perfectlab/Shutterstock

A new study, published in the journal Demography, makes a rather curious claim: Americans appear to be biologically aging far slower than they are chronologically aging. There are a bunch of implications attached to this research, but before we go into those, you’re probably wondering what biological age actually is.

Your chronological age is determined by how many times you orbit the Sun. Twenty-five orbits, 25 years old, easy peasy. As it happens, though, the concept of biological age also exists, and it’s likely mismatched with your chronological age.


As you go through life, your body develops and changes. Your blood pressure, respiratory characteristics, muscle mass, cholesterol levels, immune system resilience, and so forth could all be used as potential biomarkers for how biologically aged you are.

Results are normally compared against biomarker stats from other people the same chronological age as you. Average biological ages are then matched to the majority’s chronological age. It’s worth pointing out, however, that there’s no agreed standard as to how to measure biological age, which means this method is sometimes criticized for its subjectivity.

Either way, biological age becomes a risk indicator. If you’re 50 and your biological age is 50, you’re averagely healthy for your age. If you’re biological age is 70, then you’re unhealthy and more likely to become unhealthy is some form or another. If you’re biological age is 30, then the opposite is true.

A pair of researchers, from the University of Southern California and Yale, were curious as to how American’s biological ages had changed over time. Using several databases of biomedical data, obtained between 1988 and 2010, belonging to 21,575 Americans aged 20-79, they gave it a shot.


Biological ages were ascertained using a wide range of factors, including metabolism, specific blood proteins, organ function, breath capacity, blood pressure, and far more. They also made sure to take into account health behaviors that could be modified, including smoking, drinking, diet, and medications.

Using their sociodemographically varied data set (although still comprised of 74.3 percent white subjects), they concluded that all groups had experienced some decline in their biological age, relative to their chronological age, in that time period.

Young males showed the greatest “delay” compared to young females, and older adults experienced the greatest delays overall – changes largely explicable by alterations in smoking, weight changes, and medication.

“It is hard to say for sure, but it is likely that many of the other developed countries that show increases in life expectancy are also experiencing this due to on overall slowing of the aging process – some possibly more so than the US,” co-lead author, Prof. Morgan Levine from Yale’s School of Medicine, suggested to IFLScience.


So why does this matter? Well, at its heart, the paper has a bit of a beef with the relentless focus of health officials on the nation’s improving life expectancy.

“Increasing life expectancy has been interpreted as improving health of a population,” it begins. “However, mortality is not always a reliable proxy for the pace of aging and could instead reflect achievement in keeping ailing people alive.”

The researchers are essentially saying here that medical advances and methods may be the primary driver of lower mortality rates in the US. Treatments may not be eliminating potentially fatal diseases, but it may be preventing them from killing people for longer, for example.

The length of someone’s life cannot simply indicate how healthy they are, and the discrepancies in the biological aging delay between demographics has, as the authors note, “important social and economic implications.”


There’s only so much medical treatment can do to improve someone’s chronological age. If groups with slower delays in biological aging – say, young females – continue to fall behind, it could mean they’ll spend more of their lives in poor health, all while adding to the burden of the nation’s social support and healthcare systems.

The long and short of this study? It’s not just about the quantity; quality counts too.


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