A few years ago, a study was published reporting that men with a high narcissism score have about three times the level of the stress hormone cortisol in their saliva compared to men with low narcissism.

Original article:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0030858

Commentary:
http://www.tipsonlifeandlove.com/general-health-health/narcissistic-men-...

It seems that living as a narcissist is very stressful. A limited stress response at appropriate times is useful, however, long term chronic stress and high cortisol are detrimental to one’s health.

http://dujs.dartmouth.edu/2011/02/the-physiology-of-stress-cortisol-and-...

Therefore if, at a future date, you see news of a man with malignant narcissism in a very stressful job who has suffered a heart attack or a stroke, feel free to wonder if elevated cortisol was involved. Theists among you may consider that, “The Lord works in mysterious ways.”