While competition in the sport is occasionally depicted as brutal by the media,[28] there had never been a death or crippling injury in a sanctioned event in North America[29] until the death of Sam Vasquez on November 30, 2007.[30] Vasquez collapsed shortly after being knocked out by Vince Libardi in the third round of an October 20, 2007 fight at the Toyota Center in Houston, Texas.[31] Vasquez had two separate surgeries to remove blood clots from his brain, and shortly after the second operation suffered a major stroke and never regained consciousness.[30] While questions have been asked about Vasquez's health before his final bout, no firm indications of pre-existing problems have yet surfaced. Since he was age 35, he would have had to undergo extensive pre-fight medical screening in order to obtain a license to compete in Texas.[30]
 
This was the third verified fatality in MMA. The first was the 1998 death of Douglas Dedge in an unsanctioned fight in Ukraine. There are unconfirmed reports that Dedge had a pre-existing medical condition.[32] The second was the 2005 death of a 35-year old man only identified as Lee in South Korea. This took place in an unsanctioned event in a restaurant called Gimme Five.[33]
 
A study by Johns Hopkins University concluded, "the overall injury rate [excluding injury to the brain] in MMA competitions is now similar to other combat sports [involving striking], including boxing. Knockout rates are lower in MMA competitions than in boxing. This suggests a reduced risk of traumatic brain injury in MMA competitions when compared to other events involving striking."[34]
 
Reference: Wikipedia