Thanks for this, OP. It's interesting, as pre Pandemic I was really fit, physical job, swimming and seeing a personal trainer. He did this test on me and it came out as 64. I was 48! I was bloody gutted.
I'm now 53, I've put 3 stone on and my health has deteriorated (I now have a disability and am unable to exercise much) yet my heart age is 61.
I'll take that, to be fair, as I need all the positives I can get. My family history re heart issues <75 is decent, and I don't have diabetes or high cholesterol. (My BP issues and weight are the only thing pushing up my score)
Food for thought