The 70-year-old Bowlen will no longer be a part of the club's daily operations, the Broncos announced Wednesday. Team President Joe Ellis is adding the title of chief executive officer and will have final say on all matters.
The Broncos say the ownership of the franchise is held in a trust Bowlen set up more than a decade ago in hopes that one of his seven children will one day run the team.
"As many in the Denver community and around the National Football League have speculated, my husband, Pat, has very bravely and quietly battled Alzheimer's disease for the last few years. He has elected to keep his condition private because he has strongly believed, and often said, 'It's not about me,'" Annabel Bowlen said in a statement Wednesday.
"Pat has always wanted the focus to be solely on the Denver Broncos and the great fans who have supported this team with such passion during his 30 years as owner. My family is deeply saddened that Pat's health no longer allows him to oversee the Broncos, which has led to this public acknowledgment of such a personal health condition," she added.
"Alzheimer's has taken so much from Pat, but it will never take away his love for the Denver Broncos and his sincere appreciation for the fans."
The team issued a statement offering "our full support, compassion and respect to 'Mr. B,' who has faced Alzheimer's disease with such dignity and strength."
Business is expected to go on as usual at Broncos headquarters.
Bowlen had reduced his public appearances in recent years, although he was still a fixture at the team's Dove Valley complex and at all of its games. After acknowledging in 2009 that he suffered short-term memory loss, he stepped back from day-to-day operations in 2011 when he promoted Ellis to president.
For the first time this offseason, Ellis represented the Broncos at the annual owners meetings.
Under Bowlen's guidance, the Broncos won six AFC titles and two Super Bowls. At 307-203-1, Bowlen and New York Giants founder Tim Mara are the only three-decade owners in pro football history to win 60 percent of their games.
The Broncos' 186 home victories are the most in the NFL since he bought the team in 1984, when John Elway was his quarterback, not his front office chief, and the Broncos' five losing seasons during those 30 years are the fewest in the league over that span.
Elway, now the team's general manager, once said Bowlen's competitive nature as a triathlete when he was younger translated into his business life "and how he ran the Broncos."
Bowlen was known as much for his humility as his competitive fire, doing his best to stay out of the spotlight even as he built a winning culture and a fan base that extends throughout the Rocky Mountain region.
His style endeared him to employees and players alike.
"Words can't express the love, respect & gratitude I have for Pat Bowlen. He set the standard for team ownership. Keep Mr. B in your prayers," former Broncos receiver Ed McCaffrey tweeted.
When Bowlen received the Mizel Institute's 2013 Community Enrichment Award, Hall of Famer Shannon Sharpe said: "I would be hard-pressed to believe that there's an owner that cares more about his city, about his state, about his players than Mr. Bowlen does."
Hall of Famer Gary Zimmerman said he realized Bowlen was a different type of owner when he signed up for a turkey his first Thanksgiving in Denver, thinking it was all a joke.
"Then I come into the locker room and there's Pat sticking turkeys into our lockers," Zimmerman recounted.
During Peyton Manning's whirlwind free agency tour in 2012, Zimmerman said, he knew any other teams pursuing the four-time MVP were just wasting their time.
"I knew he'd be a Bronco before he did," Zimmerman said, "because once he visited here and met with Mr. Bowlen, I knew there was no way he could go anywhere else."