Denver Broncos owner Pat Bowlen has handed control of the team to president Joe Ellis, due to an ongoing battle against Alzheimer's disease.

Bowlen purchased the Broncos in 1984 and during his 30 years at the helm, the team has reached six Super Bowls. The Broncos won back-to-back titles in 1997 and 1998, though their most recent appearance ended in defeat to the Seattle Seahawks in February.

In May 2009, Bowlen told reporters that he was dealing with short-term memory loss. However, the team and Bowlen's family acknowledged on Tuesday that his condition had developed into Alzheimer's over the previous five years.

A statement from the Broncos read: "In recent years, Denver Broncos owner Pat Bowlen has taken a reduced role with his team while courageously and privately battling Alzheimer's disease.

"The Broncos are very saddened that Mr. Bowlen is no longer able to be part of the team's daily operations due to his condition. We continue to offer our full support, compassion and respect to 'Mr. B,' who has faced Alzheimer's disease with such dignity and strength."

Following a stint with the Broncos during the 1980s, Ellis rejoined the franchise in 1998. In 2008, he was named the team's chief operating officer before taking over as team president three years later.

"It's a really, really sad day," Ellis told The Denver Post. "It's sad for his family, his wife and his seven children. It's sad for everyone in the organisation.

"It's also a sad for all the Bronco fans who know what Pat Bowlen meant to them as an owner. It's a day nobody wanted to see happen."

Bowlen's wife Annabel also thanked the Broncos fans for their support, while NFL commissioner Roger Goodell offered his own sympathies in an official league statement.