My grandfather was born in 1915, survived 3 years in the European Theatre (including landing at Normandy,) ate like a human garbage can, and lived to the age of 82.
He had a quad-bypass in his late sixties, and had probably ridden 300,000 miles on a bike by that point. The cardiologist said, "That bike is why you're alive. You have the heart of a 20 year old, and the arteries of a corpse."
So it's all of the above: genetics, diet, lifestyle. Genetics seems to play the highest card.
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