At least 12 mixed martial arts fighters and kickboxers have died worldwide since 2007, competing in bouts or preparing for them, according to a Milwaukee Journal Sentinel review. Here is a look at the deaths.

October 2007: Mixed martial arts fighter Sam Vasquez is knocked out in the third round of a regulated fight in Houston, later dying of a subdural hemorrhage due to blunt trauma of the head.

June 2010: Michael Kirkham dies following a regulated MMA bout in South Carolina. The cause of death was subarachnoid hemorrhage of the brain.

July 2010: Kickboxer Adrienne Simmons dies after she was knocked out in a three-round bout in Orlando. A doctor was at the event, sponsored by the International Kickboxing Federation, but no ambulance. Simmons was wearing headgear. Reports did not list the cause of death.

August 2011: British kickboxer Mark Fowler dies in Australia. He collapsed after fighting five rounds and failed to regain consciousness. He died of head injuries.

December 2011: Mixed martial arts fighter Salvador Flamenco dies in Vancouver, Wash., from head injuries suffered in training bouts there.

April 2012: Mixed martial arts fighter Mike Mittelmeier dies in Bolivia in an unregulated bout. The cause of death was cerebral hemorrhage.

May 2012: Mixed martial arts fighter Dustin Jenson dies following an unregulated bout in South Dakota. Jenson watched the next fights before suffering a seizure. He died of subdural hemorrhage resulting from blunt force trauma to the head, related to an injury suffered a week earlier.

August 2012: Mixed martial arts fighter Tyrone Mimms dies following a regulated bout in South Carolina. Autopsy results were inconclusive.

April 2013: Mixed martial arts fighter Felix Elochukwu Nchikwo dies in Port Huron, Mich., in an unregulated bout. He had a cardiac arrhythmic disorder that caused his sudden death.

September 2013: Mixed martial arts fighter Leandro Souza of Brazil dies just before a weigh- in. He died in a sauna as he tried to cut 33 pounds in a week.

March 2014: Mixed martial arts fighter Booto Guylain dies in South Africa following complications resulting from a head injury experienced during a bout.

March 2014: Dennis Munson Jr. collapses and dies following his first kickboxing bout, which was unregulated, at the Eagles Club in Milwaukee. His brain was damaged, leading to organ failure, according to the autopsy.

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