"I want to focus on what I am, who I am and how I’ve been without any distractions," Cassidy told People magazine in an interview. "I want to love. I want to enjoy life."
Cassidy's publicist confirmed the report to ABC News.
Both his grandfather and mother suffered from the disease, which affects memory, Cassidy, 66, told People. The actor said that "the only way I knew [my mother] recognized me is with one single tear that would drop from her eye every time I walked into a room."
"I feared I would end up that way," he continued. "I was in denial, but a part of me always knew this was coming."
Over the past few years, Cassidy has had several brushes with the law. He also spent time in a substance rehabilitation center in 2014.
Earlier this month, Cassidy wrote on his website that he planned to retire to some degree, calling it "the most difficult decision I have ever made in my entire life."
"I will always be eternally grateful for the love and support you’ve shown me. I still love very much to play and perform live. But it’s much more difficult for me now," he wrote. "I’m not going to vanish or disappear forever."