Genetics has a huge role to play. Alberto Salazar had a heart attack at 48. Now, maybe running gave him a few years before his first incident as it sounds like he was already taking medication for high blood pressure and cholesterol.
The point being once you get into serious mileage like the 30+ miles per week, doing 15-20 mile training runs and racing 1/2 and full marathons its best to view them as personal performance goals vs health goals.
Also, as someone who has run long distance for about 10 years now, take it from me that rest is as important as the miles. Making sure you have rest build into your training plan and after your goal race. This will help you avoid burnout and injuries. Remember, all training really does is takes your body to a stressing point. Its the rest portion that allows your body to respond and adapt to the stress which in turn allows your body to perform at a higher level of performance.
The point being once you get into serious mileage like the 30+ miles per week, doing 15-20 mile training runs and racing 1/2 and full marathons its best to view them as personal performance goals vs health goals.
Also, as someone who has run long distance for about 10 years now, take it from me that rest is as important as the miles. Making sure you have rest build into your training plan and after your goal race. This will help you avoid burnout and injuries. Remember, all training really does is takes your body to a stressing point. Its the rest portion that allows your body to respond and adapt to the stress which in turn allows your body to perform at a higher level of performance.