I am (way) over 55. My father who did not exercise, smoked, and ate an extremely high fat diet had his first open heart surgery in his 50s, (eggs in bacon grease, hamburger for lunch, steak and fries for supper). Many years ago I found out that I do not make much of the good cholesterol. He probably was the same. I eat a very low fat diet, exercise, do not smoke, and my bad cholesterol is also low. Each year I get a physical and ask the doctor if I am good to dive for another year. As long as he says yes, I am good to go. End of story as far as I am concerned.