'There's nothing funny about Alzheimer's': Ronald Reagan's children lash out at Will Ferrell after it is revealed he will play their father in a COMEDY about his battle with dementia 

The children of Ronald Reagan have voiced their outrage after it emerged that Will Ferrell would be playing their father in a comedic film about his battle with Alzheimer's disease.

Patti Davis and Michael Reagan both lashed out at Ferrell on Thursday, with Michael writing on Twitter; 'What an Outrage....Alzheimers is not joke...It kills..You should be ashamed all of you.'

Patti meanwhile spoke of watching her father slowly drift away over the 10 years he fought the disease, and said she now runs a group called Beyond Alzheimer’s that provides support for caregivers and family members dealing with the disease.

'Perhaps you would like to explain to them how this disease is suitable material for a comedy,' Patti wrote to Ferrell in an open letter.

It was announced earlier this week that Ferrell would star and produce Reagan, a Black List script from writer Mike Rosolio about the actor turned president's second term.

A description of the film when it was named to the Black List said; 'When Ronald Reagan falls into dementia at the start of his second term, an ambitious intern is tasked with convincing the Commander-In-Chief that he is an actor playing the President in a movie.' 

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Mixed reaction: It was announced earlier this week that Will Ferrell (above as George Bush on Saturday Night Live) would star and produce Reagan, a comedy about Ronald Reagan

Not happy: Reagan's daughter Patti Davis (left in 2013) and son Michael Reagan (right in 2011) are lashing out at Ferrell for agreeing to be in the film

Tough subject: The film is about Reagan (above in 1982) falling into dementia during his second term as president

'I watched helplessly as he reached for memories, for words, that were suddenly out of reach and moving farther away,' wrote Patti in her letter. 

'For ten long years he drifted - past the memories that marked his life, past all that was familiar…and mercifully, finally past the fear.

'There was laughter in those years, but there was never humor.'

Patti went on to say; 'Alzheimer’s is the ultimate pirate, pillaging a person’s life and leaving an empty landscape behind. It sweeps up entire families, forcing everyone to claw their way through overwhelming grief, confusion, helplessness, and anger.

'Perhaps for your comedy you would like to visit some dementia facilities. I have - I didn’t find anything comedic there, and my hope would be that if you’re a decent human being, you wouldn’t either.'

President Reagan died in 2004 as a result of pneumonia that was complicated by his Alzheimer's 

Patti and her parents had a complicated relationship, which was not helped by the release of her memoir The Way I See It. 

The book, released in 1992, painted her mother as a remarkably cruel woman and her father as a man who emotionally abandoned his children.

Davis also wrote that her mother relied heavily on sleeping and prescription pills during her years in the White House despite her 'Just Say No' campaign.

Reagan was also accused of hiding her husband's two children from his first marriage from Davis and her brother in their childhood years.

She reportedly received a $500,000 advance for the book, which her parents responded to by releasing a statement saying; 'We have always loved all of our children, including our daughter, Patti. We hope the day will come when she rejoins our family. Toward that end, we see no useful purpose for further comment.'

Davis also did not make her mother very pleased when she posed naked for Playgirl in a 1994 issue of the magazine.  

Awful: Reagan was diagnosed with Alzheimer's in 1994 and passed away a decade later because of the disease (l to r: Ron, Nancy, Patti and Michael at his funeral)

There was a live reading of the script last March in Los Angeles with Lena Dunham, Dennis haysbert and James Brolin, who played Reagan.

Brolin previously played the president in the television miniseries The Reagans. 

Ferrell has yet to respond to these attacks from the Reagan children.