While I have seen similar things in lifelong runners, I think they are the exception to the rule.
My fellow runners in their 60s and 70s are far better looking than their sedentary peers and in far better health. That was the case 20 years ago when they were in their 40s and 50s when we first started running together.
However, even though extremely competitive seniors are far healthier than their sedentary peers, my extremely competitive running peers seem to have a disproportionately large number of heart and immune disorder problems.
Why?
Of course, it could just be I'm looking at a small sample of the overall running population but here's my take on why lifelong seriously competitive runners seem to have more problems than lifelong recreational runners. I think it's just because we push our bodies harder.
As our cells age, they become less efficient at producing energy and less efficient at removing the waste byproducts of energy production from the body. As competitive runners we produce massive amounts of energy byproducts (compared to our sedentary peers and even to recreational runners) that must be rapidly removed from the body or else they cause long-term health problems.
When you're young, you can survive on the belief "if the furnace is hot enough, it will burn anything." But with age, you can no longer get away with that approach.
Eating healthy is a big part of the solution of staying healthy as we get older, but as extreme exercisers reach advanced age, it's not enough.
As we age... 60 for some of us, 50 for others... our cells become so inefficient that that they simply cannot get enough of the nutrients they need from even the healthiest of diets to operate to keep every system of the body operating as efficiently as they did when we were in our teens.
To me, this does not mean that you should quit training seriously and become a recreational runner instead of a competitive runner. To me, it means that serious runners need to supplement their diets with nutrients that have been shown to reduce inflammation, counter the effects of antioxidants, and allow muscles to recover faster from extreme exercise.
Since there are some studies that seem to show a possible link between various types of cardiovascular disease and extreme endurance exercising, I take several supplements recommended by my cardiologist for overall heart and arterial health. Also, starting at age 70, I started seeing a cardiologist twice a year to try to catch any minor heart problems before they become major heart problems.
If you're on Medicare, this is free! Granted I have to come out of pocket for the supplements and for a few of the cardiac tests but overall it's far, far less expensive than open heart surgery... or a funeral, for that matter.
EDITED: Oh and as another poster said... you must add weightlifting to your routine if you're not already doing so.