If you've ever been told "you look good for your age," take it as the compliment it's meant to be—some people can't say the same. A study published in the Proceedings of the National Academy of Sciences finds people age at what the Guardian calls "wildly different rates," with biological ages not matching up to their chronological ones.

Researchers studied 871 New Zealanders born in 1972 or '73 at the ages of 26, 32, and 38. Using a set of 18 biological markers such as blood pressure, cholesterol levels, and metabolism, scientists calculated each subject's biological age—and while most came in around where they should be, there were others who clocked in as either "younger" or "older." "The overwhelming majority are biologically in their mid-40s or younger, but there are a handful of cases who are in pretty bad shape," one of the study's authors says, per the Guardian.

One "extreme case" had the unfortunate designation of basically being a 61-year-old, the paper notes. And those who ranked on the "older" side of things didn't just suffer the indignity of being given this label.

"Already, before midlife, individuals who were [aging] more rapidly were less physically able, showed cognitive decline and brain [aging], self-reported worse health, and looked older," the researchers write.

Why knowing who seems to age faster than others is important: Scientists hope to be able to study younger people's physiology for warning signs of diseases they haven't yet developed so that anti-aging therapies can be honed and maximized.

"What we need are measurements that can show whether these therapies are working, so we don't have to wait 50 years to see if someone is still alive or not," the scientists say, per the Guardian.

(A 3-year-old Oklahoma girl who doesn't appear to be aging at all still looks like a baby.)

This article originally appeared on Newser: You May Be Aging More Quickly Than Your Peers

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