It was horrifying to watch my Aunt Minnie go through dementia. No one had any clue she'd progressed into dementia because when you called to see how she was doing she'd chat just like old times, when you visited she was just as charming and friendly as ever, you simply had no clue. But very quickly she'd started forgetting basic things - like eating - but she was happy, and when you called to check up on her she'd be her normal old self so we had no clue.
Then one day she left the house and forgot where she lived and that's when we realized what was going on.
What made me so mad wasn't that we didn't catch it, it was the fact the doctor told us had she not done that she'd likely have died in her sleep due to lack of nutrition within the next month. She went from a happy woman who was, unknowingly, starving herself to death to a woman who lived in a care home for 5 years as we watched her slowly lose herself - in the end she'd forgotten how to speak or even recognize her name. She looked like a frightened animal at the end, stuck in a bed unable to move because she'd forgotten how to even move - abject terror on her face as she struggled to breathe.
I offered to stay with her and keep her from burning the house down while she starved herself to death, but I was told "that would be cruel!" so instead I watched the nursing home torture her for half a decade while she called us every 30 minutes for days on end begging us to take her home only to calm her down and then have her forget and start the whole thing over.
Dementia / Alzheimer's runs in my family, you better believe I'd be down for a test like this every year during my annual doctor visits - I wanna know I'm gonna lose it well before I lose it so I can enjoy my last days having fun and make memories with the family they'll never forget!