Jerry Quarry, pictured above in 1972, died on Sunday at the age of 53. Left: Quarry in action against Muhammad Ali on October 26th, 1970. He fought Ali twice for the heavyweight title but lost both times.

Former heavyweight boxer Jerry Quarry, who twice fought Muhammad Ali and lost two title shots, died on Sunday at the age of 53 after a long descent into dementia brought on by repeated blows to the head, his niece said.

Quarry died at Twin Cities Hospital in Templeton in central California. He was admitted a week ago with pneumonia but his niece, Sheri Coolbagh, said that had been brought on by dementia pugilistica, which is brain damage caused by blows to the head.

The progressive malady, similar to Alzheimer's disease, left Quarry virtually helpless. "He died of complications to pneumonia - brought on by dementia," said Coolbagh, who added that Quarry had suffered for 14 years from dementia which had greatly worsened in the past three years. Quarry, a native of Los Angeles, compiled an impressive professional record with 33 knockouts. He won his first 20 bouts before losing a 10-round decision to Eddie Machen in 1966. Quarry bounced back to win his next 10 fights, twice defeating former champion Floyd Patterson in 1967.

After Ali was stripped of the World Boxing Association crown, Quarry lost a disputed 15-round title bout to Jimmy Ellis on April 27th, 1968. Fourteen months later, he got another shot at the belt, but was knocked out by Joe Frazier in the seventh round in New York.

On October 26th, 1970, Quarry was Ali's first opponent after his three-and-a-half-year exile and proved easy pickings. Ali knocked him out in the third round on his road back to the championship and sent him to the canvas again in the seventh round on June 27th, 1972.

Quarry stopped Ron Lyle in 12 rounds in February 1973 and scored a first-round knockout of Earnie Shavers 10 months later.

Frazier knocked Quarry out again in June 1974 and Ken Norton also beat him by knockout in March 1975. He fought again in 1977, then was inactive until 1983, when he posted victories over a pair of no-name opponents.

Out of money and already showing signs of blunt force trauma, Quarry returned to the ring on October 30th, 1992, and lost in six rounds to Ron Cramner.

He founded the non-profit Jerry Quarry Foundation to prevent other athletes from following in his footsteps.