There are many ways to define age. There’s the calendar. There’s how old you feel. And now, artificial intelligence can determine your true biological age by analyzing chest X-rays.

So while you might look and feel great, the true answers about your age lie within the body. That’s where AI comes in. Researchers at Osaka Metropolitan University in Japan have developed an advanced AI model that analyzes chest X-rays to accurately estimate a person’s age. More significantly, it has the potential to identify the cumulative effects of chronic diseases.

To develop their AI model, the researchers first obtained chest X-rays from more than 36,000 healthy people from a 13-year period. Then, they gathered similar images from another 34,000 people with diseases such as high blood pressure and chronic obstructive pulmonary disease.

In the healthy patients, there was a strong correlation between their AI-estimated age and their chronological age. Among the people with chronic diseases, the difference between their actual and AI-estimated ages was linked to their medical issues. In other words, the higher the AI-estimated age compared with their chronological age, the more likely those people were to have certain diseases.

The researchers say the AI technology could someday give doctors better insight into a person’s true age — one that’s based on conditions inside the body rather than the pages on a calendar. That, in turn, has the potential to lead to more accurate life expectancies and a better understanding of the effects of chronic diseases.

So, in the future, “looking your age” may be less about your face … and more about what’s happening inside your chest.