What s next Making a comedy at the Humane Society about euthanizing pets?  Patti Davis, daughter of late President Ronald Reagan and Nancy Reagan, penned a moving open letter to actor Will Ferrell on Thursday criticizing his involvement in an upcoming comedic film that will satirize President Reagan s tragic battle with Alzheimer s disease.The film, based on a 2015 Black List script, centers on a fictional story in which President Reagan begins suffering from dementia shortly after a landslide reelection victory in 1984. A young aide must convince Reagan that he is an actor playing the President in a movie.Ferrell is attached to play Reagan in the film and will produce it under his Gary Sanchez Productions banner.Here is the letter Patty Davis penned to Ferrell:Dear Mr. Ferrell,I saw the news bulletin   as did everyone   that you intend to portray my father in the throes of Alzheimer s for a comedy that you are also producing. Perhaps you have managed to retain some ignorance about Alzheimer s and other versions of dementia. Perhaps if you knew more, you would not find the subject humorous.Alzheimer s doesn t care if you are President of the United States or a dockworker. It steals what is most precious to a human being   memories, connections, the familiar landmarks of a lifetime that we all come to rely on to hold our place secure in this world and keep us linked to those we have come to know and love. I watched as fear invaded my father s eyes   this man who was never afraid of anything. I heard his voice tremble as he stood in the living room and said,  I don t know where I am.  I watched helplessly as he reached for memories, for words, that were suddenly out of reach and moving farther away. 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.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.Twice a week I run a support group called Beyond Alzheimer s for caregivers and family members of those with Alzheimer s and dementia. I look into haunted eyes that remind me of my own when my father was ill. I listen to stories of helplessness and loss and am continually moved by the bravery of those who wake up every morning not knowing who their loved one will be that day, or what will be lost. The only certainty with Alzheimer s is that more will be lost and the disease will always win in the end.Perhaps you would like to explain to them how this disease is suitable material for a comedy.