Thread title: 100%, not more, not less...
Seriously: There are steroid users in the sport, it involves organized crime on many levels, it contains pretty disturbing traumas inflicted to the head and body, it demands very harsh training regimens and many aren't making enough to secure their old age.
Result: death from drug and alcohol abuse, suicide, murder, longterm injuries and suchlike is probably way higher than in most segments of the population.