“The Partridge Family” star David Cassidy announced Monday that he has been diagnosed with dementia. The singer, whose mother and grandfather also suffered from the condition, “always knew this was coming,” he said during an interview with People magazine.

Initially, he was in denial about his diagnosis, Cassidy said. However, he always feared he would eventually develop dementia, which is a form of Alzheimer’s disease that causes severe memory loss and decline of language and other cognitive functions.

Cassidy’s announcement came after he failed to remember the lyrics to songs he’s been singing for the last 50 years of his life during a concert in Agoura Hills, California, Sunday night. Along with slurring words to his songs, the 66-year-old also reportedly fell off the stage during his performance.

Before ending the concert, Cassidy reportedly announced he would be retiring from his musical career and said that his Sunday night show would be his last.

“I want to focus on what I am, who I am and how I’ve been without any distractions,” he told People. “I want to love. I want to enjoy life.”

About 5.4 million Americans were suffering from Alzheimer’s disease, 11 percent of which were at least 65 years old, according to the Alzheimer’s Association’s 2016 Facts and Figures report. Although it was unclear exactly how many people living in the U.S. were battling various forms of dementia – there are five different classifications of dementia – the Alzheimer’s Association estimated about 14 percent of people 71 and older in the U.S. suffer from the disease.

Although symptoms of Alzheimer’s and dementia can vary and be hard to diagnose, symptoms normally include memory loss that can disrupt daily life, difficulty completing routine tasks at home or work, confusion with dates and time, decreased poor judgment, new problems speaking like slurred words or stuttering, inability to replace steps and increased instances of misplacing belongings, changes in personality and mood including apathy and depression and increased anxiety, agitation and trouble sleeping.