Ronald Reagan's Daughter Remembers Being by His Side as Alzheimer's Took Its Toll: 'Courage and Such Grace'

When doctors first noticed that former President Ronald Reagan had begun to develop symptoms of dementia in 1989, his daughter Patti Davis remembers now, it "didn't feel real."

A fall on a horse had led to a brain scan, which showed signs of plaque, but it wasn't yet clear that it would develop further. Reagan's official diagnosis with Alzheimer's in 1994 — and his corresponding letter to the world announcing he had the disease — was different, Davis says. "It was the start of a journey that I knew nothing about."

Speaking to PEOPLE after the release of a new book about Alzheimer's caregivers, Floating in the Deep End, Davis says that her dad's diagnosis came "at a terribly dark period in my life."

"I had sold my house at the bottom of the market, I had very little money. I knew no one in New York, where I was living, and had tried to run away from an abusive relationship," she says. "It was just like everything I touched went wrong. I was really thinking I didn't need to be here. Like, who would miss me? I was emotionally tired."

But watching her dad deal with his suffering somehow helped her with her own.

"When this happened I suppose it could have taken me farther down that dark road," Davis says, "but it actually had the opposite effect. Because I thought, 'My father is facing this with such courage and such grace, and my despair paled in comparison to that.' This was bigger than whatever I was going through, and it meant that I had something bigger to focus on. I wanted to be there for that."

In his letter announcing his diagnosis, Reagan looked ahead to the coming day when he would need support: "At the moment I feel just fine. … Unfortunately, as Alzheimer's Disease progresses, the family often bears a heavy burden."

Davis being there for her father came with its own set of challenges, though — including working through a fractured (and well-documented) relationship with her mother, former First Lady Nancy Reagan, who was the president's chief defender and most ardent supporter.

Davis says the changes in her father's health provided an opportunity to get to know her mother in a different way and to define the relationship in her own terms.

"As much as Alzheimer's, and the person who has it, comes to dominate your life, it also presents you with an opportunity to free yourself from the domination of the past," Davis writes in Floating in the Deep End. "The dynamics that were once in place don't need to define the future. I'd spent so many decades longing for what I was never going to get from my parents. Alzheimer's made me realize that I had to be the one to change."

Speaking to PEOPLE, Davis says she learned an important lesson about parent-child relationships while tending to her father in his later years.

"Here's the thing that I came to: Ultimately, the most important thing is not that the parent belittled you, or made you feel worthless, or deserving of punishment," she says. "Ultimately, what's most important is that you believed them. That's the voice that trails you for all those years. And that's where the area of change has to be."

While she learned to better communicate with her mom, Davis also learned to see her dad in a new light, writing that the disease enabled her to know him "a bit better" as he retreated into an almost child-like version of himself.

"Alzheimer's moves a person back through time," she writes. "If you're willing to follow them down that road, you learn things you might never have learned otherwise."

As the former president, a towering man in both stature and presence, grew smaller, Davis says he became "stripped away, to the essence of himself."

"My father at his essence was a sweet, gentle person," she says, recounting a day sunlight streamed through the window of his California ranch and onto the floor. "He thought something had spilled something on the floor and he tried to wipe it up. That was his instinct — I have to wipe this up so no one else has to."

Davis says she knew her father's true temperament well before his Alzheimer's diagnosis. But knowing that the end was on the horizon meant that she was able to appreciate him without any hang-ups.

"There [had been] so much else in the way — my wanting him to be a more available, present father got in the way of really appreciating and being grateful for the human being he was underneath everything," she says now. "It was kind of fascinating to see shadows of that near-sighted boy with an alcoholic father who was very alone from a very young age and learned to create his own world."

Even in total silence — watching the way Reagan's eyes lit up when he saw an old photo, or the way his hands would move up and down, clutching an invisible object while he sat in his favorite chair (a surefire sign, says his daughter, that the avid equestrian was holding the reigns of a horse in his mind) — Davis learned more about her father as the disease took its toll.

More challenging, she says, was applying those lessons to her mother.

"Finally, instead of feeling resentful, I felt sympathy for her. She created this family that was pretty broken, and now she was losing the love of her life," Davis says. "It's not that we didn't want to be there, but nobody knew how."

Davis continues: "I turned a corner to thinking, 'How sad for her. She could have had that, but nobody knows how to do it and she doesn't know how to ask for that or foster that now.' "

In 2004 — 10 years after announcing his diagnosis to the world — Ronald Reagan died at age 93 in Bel Air, California, of complications from Alzheimer's. As Davis writes in her book, he took his final breath while staring into his wife's eyes and closing his own one last time.

Mrs. Reagan died 12 years later, in 2016 at the age of 94.

Looking back on her own experience of that last decade of her dad's life, Davis admits the journey was a lonely one. She found that the one of the best ways to cope with the stresses of being a caretaker was to find others in a similar situation.

"People would recognize me in Manhattan and give me snippets of information about a parent or grandparent or spouse and then they'd be gone," she says with a laugh. "I felt like I was in the French underground. There was really no information about it so people just told who they could."

Recognizing an appetite for a support group for caregivers, Davis established Beyond Alzheimer's eight years after her father's death. She then worked on getting the program licensed so it could expand beyond Los Angeles, but she says she was met with a lot of resistance from hospitals around the country.

"A lot of them said, 'This just isn't in our budget.' I thought okay, fine, I'll put the information I've learned out there in a different way and at least people have a resource," Davis says.

That resource comes in the form of her new book, which includes both anecdotes about her father's experience as well as the tools she's used to cope as a caregiver.

"We've gotten a lot better about talking about the disease but I don't think there is enough care for the caregivers," Davis says.

And after all it is the caregivers, she writes in her book, that feel perhaps most adrift due to a dementia diagnosis: "For the decades of my father's illness, I felt as if I were floating in the deep end, tossed by waves, carried by currents, but not drowning."

Now on dry land, so to speak, Davis hopes that others can view the very daunting experience the way she has come to remember it.

"Yes, someone's cognition is crumbling, their recognition is fading. But it allows you a wider lens to look at that person," she says. "There's always a different way to look at it."