Someone is diagnosed with Alzheimer's every 70 seconds. At least they'll forget about it in a minute.
Why would you make a joke about people with Alzheimer's disease?
I'm just reminding myself it's a fact that people with Alzheimers have short memories.
Alzheimers is a terrible disease that doesn't deserve being marginalized by humor. Save the humor for a more appropriate subject.
People with Alzheimers are dating people without it in real life because they can't remember.
Alzheimer's is a fatal disease and the memory loss causes a lot of pain for the people who have it and their families. You should consider your audience before you tell jokes like this. If you think about how the joke might make someone feel, then you might not find it so funny.