For years I used to quote Dennis Leary’s routine where he said he would continue to smoke because it didn’t matter how you treated your body because you’d end up like Jim Fixx. As I wrote eariler, Jim Fixx was an avid running enthusiast who suddenly dropped dead while running in his early 50’s. I, too, found this incredibly funny and used his situation as a reason to not run, along with other scary running stories (such as a girl who was so addicted to the endorphin “high” you get while running that she ignored the pain of her shin splints and caused permanent damage, etc.).
Lo and behold, some basic research turns up Jim Fixx’s autopsy, which indicates that he neglected his cholesterol which caused 95% blockage of one artery, 85% of another, and 50% of a third, eventually causing a massive heart attack. So it wasn’t really running that killed him; it was the lack of importance he put on regular cholesterol checkup and maintenance, coupled with a poor family history (a heart attack killed his father at age 42).
So, if anything, Fixx’s running history probably extended his life a few years.