If you could turn back time, you might use this old-timey clock.
Photo: North Charleston/Flickr

People age at different paces. If you went gray before all your friends, or found wrinkles creeping along your forehead in your 20s, you might already be well aware of the inequalities bestowed by the passage of time. But it’s not just our appearance that changes at a varying rate. This difference in how our bodies age is measured by what’s known as “biological age.”

Increasingly, scientists have been interested in studying the differences between biological age and chronological age in order to better understand why some people age better than others. Such research can help shed light on things that actually work to help us live longer, better lives. And a new study from the University of Southern California and Yale University, published in the journal Demography, suggests that Americans might already be doing something right.

Today, we live longer lives than ever, and researchers wondered whether changes in biological age over time—rather than medical advances alone—are a factor in that. What they found suggests that Americans may indeed be aging more slowly than they were two decades ago.

To arrive at that finding, researchers looked at two data sets from the National Health and Nutrition Examination Survey, one collected between 1988 and 1994, and the other between 2007 and 2010. Using indicators like metabolism function, inflammation, and organ function, along with measures like levels of hemoglobin and total cholesterol, they calculated biological age for people in each data set, and compared it to chronological age. In the more recent group, biological age was generally lower for the same age groups. The difference between the two time periods was biggest in older adults.

Some of that slowing of the aging process, they concluded, was the result of changes in behaviors, such as a trend away from smoking.

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While not a definitive take on the subject, the study makes several important points. Pushing major health problems farther toward the end of life, of course, would not only make for healthier people, but also place less strain on medical and financial resources that deal with the sick. And the study identifies areas for future investigation, including smoking and exercise, that might help us better understand how lifestyle and environmental factors contribute to overall health over a lifetime.