Not sure if this has been posted yet.
Serious distance runners would fall into this high-risk category of exercising at least 7.5 hr/week. This group was twice as likely to suffer from heart disease as those who exercise only a moderate amount. These stories about the study say only white men showed this correlation. Black men were not affected. Experts commented that the hypothesis is stress of "excessive time" exercising sustains elevated cortisol levels, causing increased calcification of the arteries.
http://nypost.com/2017/10/17/you-can-exercise-yourself-to-death-says-new-study/
http://www.medicaldaily.com/exercise-bad-you-too-much-may-be-unhealthy-your-heart-422189
Anyone gotten hold of the actual research paper? Please tell me this was some shoddy research.