Actor Gena Rowlands, who starred in 'The Notebook,' has Alzheimer's disease, her son says

Actor Gena Rowlands has Alzheimer's disease, her son, filmmaker Nick Cassavetes, has revealed.

Cassavetes, who directed his mom in "The Notebook," shared the news while discussing the film's 20th anniversary with Entertainment Weekly . In the romantic cult classic, Rowlands played the older version of the lead character Allie — played in her younger years by Rachel McAdams — who develops dementia.

"I got my mom to play older Allie, and we spent a lot of time talking about Alzheimer's and wanting to be authentic with it. And now, for the last five years, she's had Alzheimer's," Cassavetes said. "She's in full dementia. And it's so crazy — we lived it, she acted it, and now it's on us."

With a career spanning nearly seven decades across screen and stage, Rowlands has a resume stacked with more than 100 film and TV credits, two Academy Award nominations, an Honorary Academy Award, four Emmy Awards, two Golden Globe Awards and multiple other nods and wins. The 94-year-old is known for collaborating with her husband and the father of her three children — including Nick — John Cassavetes.

John also directed Rowlands' mother, Lady, in multiple films. In an interview with O magazine in 2004, Rowlands said her decision to play Allie in "The Notebook" was difficult because of her mother's health before her death in 1999.

"This last one — 'The Notebook,' based on the novel by Nicholas Sparks — was particularly hard because I play a character who has Alzheimer's," Rowlands said. "I went through that with my mother, and if Nick hadn't directed the film, I don't think I would have gone for it — it's just too hard. It was a tough but wonderful movie."

Alzheimer's disease is a progressive brain disease that causes the brain to shrink and cells to eventually die, according to Mayo Clinic . It's the most common cause of dementia — the gradual decline in memory, thinking, social skills and behavior — which can affect a person's ability to function.

It's not fully understood why people develop Alzheimer's disease, though causes likely include a combination of age, genetic, environmental and lifestyle factors, according to the National Institute on Aging . Having a family history of the disease doesn't mean someone will surely have it, but it does increase the odds. And although older age doesn't cause the disease, it's the most important known risk factor.

Mayo Clinic states about 6.5 million people aged 65 and older in the U.S. have Alzheimer's disease, and of the approximately 55 million people with dementia globally, 60% to 70% are estimated to have Alzheimer's disease.