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It was 45 years ago today that Bruce Lee lay down for a nap in the Hong Kong home of actress Betty Ting and never got up. The official cause of death for the then-32-year-old remains cerebral edema, or brain swelling, caused by a hypersensitivity to the painkiller equigesic.

But nearly a half century later, that story is still not convincing some of the Kung Fu legends biggest fans.

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The wildest conspiracy theories suggest that he was killed by ninjas, bad feng shui, the mafia or a mythical delayed "dim mak" death punch.

Most serious people agree that it was brain swelling that did Lee in, but there's little agreement on what caused it. The South China Morning Post runs through the possibilities today and begins by dismissing the accepted notion that the painkiller killed Lee:

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Actress Betty Ting Pei, who was with Lee when he died in her flat in the city’s Beacon Hill neighbourhood, said she gave Lee an Equagesic pill when he said he had a bad headache, shortly before he died.



However, there was insufficient medical evidence to prove beyond doubt that the drug caused the condition and a verdict of death by misadventure was recorded at the inquest. Neither meprobamate nor aspirin, the two constituents of Equagesic, are known to cause a cerebral oedema.

Another possibility is that Lee had a bad reaction to cannabis, which was found in his system upon his death. But that probably wasn't it either.

Hong Kong doctors believed that the cerebral oedema could have been brought on by ingesting cannabis – traces of hash were found in Lee’s stomach and intestine at the time of his death.



But no causal link between cannabis and cerebral oedema has ever been documented, and this theory has been dismissed as speculation.

That leaves two other theories that don't emanate from the lunatic fringe. One that's been around for a while suggests that Lee died because he was epileptic, something that wasn't discovered until 20 years after his death.

The latest theory, advanced in the new book Bruce Lee: A Life, is that Lee died of heat stroke after having his sweat glands removed. The book's author, Mathew Polly, wrote about the theory for History.com:

A common finding in the autopsy of heat-stroke victims is cerebral edema. “A person who has suffered one heat stroke is at increased risk for another,” says Dr. Lisa Leon, an expert in hyperthermia at the U.S. Army Research Institute of Environmental Medicine. “Patients experience multi-organ dysfunction during the hours, days and weeks of recovery, which increases the risk of long-term disability and death.”

As he notes, the day on which Lee died was the hottest day of July in Hong Kong, which leads him to conclude that the cerebral edema that killed Lee "seems clearly to have been caused by heat stroke."