hs-CRP is well known as a useful biomarker and it is cheap to test too. If you look at page 13 of the GrimAge 2 paper, you'll see CRP is one of the factors most negatively correlated with their aging clock, in fact basically as strong of a negative impact as smoking. https://escholarship.org/content/qt6k46n006/qt6k46n006.pdf

This new news is about research published in the Journal of the American College of Cardiology.

It's definitely not some marketing fad.